MSR® Water Treatment & Hydration FAQ

The information presented here is intended to be a supplement to your filter or purifier instruction manual. Please refer to the manual when performing any of the procedures described on our web site.

Click on a category, then choose a question to view its answer.

General Water Treatment FAQ

Why do I need a filter or purifier?

Virtually all surface waters are contaminated with at least one of the three types of potentially disease-causing microorganisms: protozoa, bacteria, and viruses. A 1992 study found that 97% of U.S. rivers and lakes contain one or both of the protozoan parasites Giardia and cryptosporidia.

While it is true that you can drink directly from many water sources, it is critical to understand that each time you do, there is a chance of ingesting one of these bugs. Infection symptoms can range from an upset stomach to debilitating illness and, depending on where you are, can mean anything from a simple inconvenience to a life-threatening situation. Since microorganisms are impossible to see, taking the proper precautions with any water can help to ensure a safe trip.

What is the scoop on protozoan parasites?

Protozoa are the largest of the waterborne bugs measuring in the one-micron range. Giardia and cryptosporidia are the most infamous of the group. The infective cysts and oocysts of protozoa are extremely robust and can survive for months in a water source. They thrive in domestic and wild animals as well as humans. Cryptosporidia oocysts are known for their resistance to chemical treatment. Most disinfectants are ineffective, and the few that are require long dwell times to do the job.

What is the scoop on bacteria?

Bacteria are an order of magnitude smaller than protozoa measuring in the 0.5 - 2 micron range. The most well-known bacteria are E. coli; others include Leptospira (which causes Leptospirosis), Campylobacter, Salmonella, and Shigella. Bacteria aren't as hearty, surviving in water only for weeks instead of months. However, unlike protozoa and viruses, which require a host to multiply, some bacteria can grow in water and so can be found in higher numbers than protozoa and viruses. Bacteria, like protozoa, are often carried by both animals and humans. Because of this, many water sources are contaminated with bacteria. Beware especially of sources near agricultural operations.

What is the scoop on viruses?

Viruses are the smallest type of pathogen, ranging between 0.02 - 0.3 microns. Waterborne viruses are very resilient and can survive for months. It is important to note that viruses are generally species-specific. In other words, those that infect animals do not infect humans and vice versa. Because of this, and the well-maintained sewage systems in developed countries, not as many water sources are contaminated with human viruses. However, in heavily traveled backcountry areas, viruses can be present where human waste is not disposed of properly. In developing countries with little or no sewage control, viruses are often widespread and purification in such countries should be standard procedure for all travelers.

What happens if I drink water that contains viruses, bacteria and protozoa?

First, it will usually take more than one organism to make you sick—around 10 for protozoa and viruses and 10 to 1,000,000 for bacteria depending on the species. The onset of symptoms can start anywhere from 10 hours to several weeks from the point of infection depending on the type and amount ingested, and constitution of the individual. Symptoms can range from nothing to diarrhea, abdominal cramps and pain, nausea, vomiting, muscle cramps, fever, fatigue, headache, chills, loss of appetite, and, in the case of hepatitis, dark urine and jaundice. Symptoms usually dissipate in a couple of days or weeks, again depending on the three elements above. Healthy adults will generally knock the illness without needing medical attention and without lasting effects. However, infants, young children, elderly, pregnant, and immune-compromised individuals are at higher risk of needing medical attention or having complications from an illness. Your location—a remote basecamp in Pakistan or a day hike close to home— will play a key role in the severity of your illness, should you become infected. For more information on diseases caused by specific pathogens, please visit

How is a filter different from a purifier?

A filter actually removes matter and microbes from the water while a "purifier" can employ a variety of methods to disinfect the water (such as UV or MIOX® or combination system like the MSR Sweetwater® purifier). A purifier must meet the EPA Guide Standard for Testing Microbiological Purifiers, which requires inactivation of all three classes of microbes: protozoa, bacteria and viruses. Filters in general claim to remove only protozoa and bacteria, making it adequate for most travel in developed countries. Some filters alone can qualify as a purifier, but since they are filtering to such a small pore size, they tend to clog quickly. Essentially the classification as a "purifier" means that the device must be capable of inactivating viruses, as well as protozoa and bacteria.

What do MSR filters remove from the water?

MSR microfilters remove protozoa and bacteria. The microfilters (MSR Sweetwater® and Miniworks®) that contain carbon can also reduce tastes, odors, some chemicals, pesticides, and herbicides.

What does inactivate mean?

Inactivate means to damage a microorganism sufficiently to render it harmless.

How do I decide whether a filter or a purifier is best for me?

To decide whether you need a filter or a purifier, two important factors must be evaluated: water sources and susceptibility.

When evaluating water sources it is important to keep the following in mind: In general, protozoa and bacteria infect both animals and humans and are transmitted to water sources by animal and human waste. In contrast, waterborne viruses are species-specific and therefore transmitted to water sources by human waste alone. As a rule of thumb, remote areas with few people require (at least) filtration while popular areas with many human visitors require purification. If traveling in developing countries with poor sanitation, purification will be your safest choice.

Susceptibility is another good way to determine needs. If the treated water is to be consumed by infants or young children, elderly, or pregnant or immunocompromised individuals, then it is essential to use a purifier for the highest level of protection. Purification is also best for people who tend to get sick. If you rarely get sick and do not fit into any categories mentioned above, then filtration may be adequate depending on the water source.

What pore size or micron rating are the MSR filters?

Micron ratings aren't always the best way to gauge effectiveness. Test procedures for micron ratings vary so greatly that comparing them is misleading. In addition, micron ratings for filters do not tell you how the product will perform with actual bugs. There is an EPA Guide Standard for Testing Microbiological Purifiers, which describes how to test products to determine if they are removing or inactivating the proper number of pathogens in different types of water throughout the life of the device. When looking for a microfilter or purifier ask if the product has been tested according to the EPA Guide Standard and passed. For a microfilter, meeting the EPA Guide Standard means removing 99.9% of protozoa and removing 99.9999% of bacteria in all required water types. To be classified as a purifier, the device must meet the EPA Guide Standard for the removal of protozoa and bacteria as well as virus which must be inactivated to 99.99% in all required water types. All of the MSR filters and purifiers have passed the levels of inactivation required by the EPA Guide Standard with flying colors.

Will my filter or purifier protect me from bioterrorism?

As a result of the September 11 attack and the following concerns about bioterrorism, we have received a number of inquiries regarding our microfilters' ability to protect against such threats. MSR microfilters will protect you from harmful microorganisms that are 0.2 microns or larger. The anthrax bacteria, for example, measures about 8 microns and would be removed by all MSR filters. Additionally, if a water reservoir were contaminated with a biological agent, it is unlikely that enough organisms could be added or would survive the treatment process of the water plant to provide an infectious dose at the tap. Our water supply is more likely to be compromised or cut off completely as a result of a natural disaster, such as an earthquake or hurricane, or by a general state of disorder following any kind of attack or natural disaster. By including a good water treatment device (and knowing how to use it) in your emergency kit, you will be prepared for most situations.

How will tannins (tea-colored water) affect my filter or purifier?

MSR filters will remove some tannins from the water you are filtering. Like other contaminants, they will clog your filter over time, requiring you to clean the cartridge. Tannins will react with disinfectants and can make treated water taste unpleasant. If possible, look for a clear water source to prolong the life of your filter and improve the taste of purified water.

Do MSR filters and purifiers remove chemical contaminants from the water?

MSR filters and purifiers provide microbiologically safe drinking water. The carbon in the filters and disinfectant of the purifiers will adsorb or react with some chemical contaminates such as herbicides, pesticides, and volatile organic compounds (VOCs). However, MSR filters or purifiers will not protect you from high chemical concentrations or heavy metal contamination. Do your best to avoid water sources such as mining tailing ponds or those near agricultural operations.

What is the warranty on MSR filters and purifiers?

MSR filters and purifiers come with a limited warranty. Contact our Warranty and Repairs Department at 1-800-531-9531 if there are any problems with your filter or purifier and they will be happy to help with solutions.

Understanding Prop 65

What is California Proposition 65?
Proposition 65 is the Safe Drinking Water and Toxic Enforcement Act passed by voters in the State of California in 1986. The act was created to inform people about possible exposure to chemicals known by the State of California to cause cancer, birth defects and/or other reproductive harm.

What are the requirements of Proposition 65?
Proposition 65 requires that the Governor of California maintain and publish a list of harmful chemicals. The list is updated annually and includes chemicals that can be found in solvents, drugs, dyes, food additives, by-products of certain processes, pesticides, and tobacco products.

A chemical is listed if it has been classified as a reproductive toxicant or carcinogen by an "authoritative" organization on the subject. The U.S. Environmental Protection Agency, U.S. Food and Drug Administration, National Institute for Occupational Safety and Health, the National Toxicology Program, and the International Agency for Research on Cancer are considered authoritative for carcinogens. For reproductive toxicants, the authorities are the U.S. Environmental Protection Agency, U.S. Food and Drug Administration, National Institute for Occupational Safety and Health, and International Agency for Research on Cancer. Chemicals will also be listed if they are required to be labeled or identified as a carcinogen or as a reproductive toxicant by an agency of the state or federal government.

Why has MSR placed a Proposition 65 label on its products?
Any company with 10 or more employees operating or selling products within the State of California must comply with the requirements of Proposition 65. To comply, businesses are: (1) prohibited from knowingly discharging listed chemicals into sources of drinking water; and (2) required to provide a "clear and reasonable" warning before knowingly and intentionally exposing anyone to a listed chemical.

A Proposition 65 warning means that the business has evaluated the exposure and has concluded that it exceeds the "no significant risk level," or that the business is providing a warning based on the presence of a "listed" chemical without actually evaluating the exposure.

MSR is providing a warning based on our knowledge about the presence of one or more listed chemicals without attempting to evaluate the level of exposure. While using an MSR product, the exposure to a "listed" chemical may be well within the "no significant risk" range, but out of caution, we have placed the Proposition 65 warning labels on our products.

Are consumers who are using an MSR product with a Proposition 65 warning at risk?
The California government states: "The fact that a product bears a Proposition 65 warning does not mean by itself that the product is unsafe." The government also explained, "You could think of Proposition 65 more as a 'right to know' law than a pure product safety law."

A Proposition 65 warning means that the product contains one or more listed chemicals. By law, a warning is required unless the business proves that the exposure to the chemical poses "no significant risk." The "no significant risk" level for carcinogens is defined as the level which is calculated to result in not more than one excess case of cancer in 100,000 individuals exposed over a 70-year lifetime. Therefore, if you are exposed to the chemical in question at this level every day for 70 years, theoretically, it will increase your chances of getting cancer by no more than 1 case in 100,000 individuals so exposed.

The "no significant risk" level for reproductive toxicants is defined as the level of exposure which, even if multiplied by 1,000, will not produce birth defects or other reproductive harm. Therefore, the level of exposure is below the "no observable effect level," divided by 1,000. (The "no observable effect level" is the highest dose level which has not been associated with observable reproductive harm in humans or test animals.) For further information about California's Proposition 65, please visit

HyperFlow FAQ

What is Hollow Fiber technology?

Hollow fiber is the filtration media used in both the HyperFlow™ Microfilter and the AutoFlow™ Gravity System. Commonly used in areas such as municipal water filtration systems and medical applications, this technology is ideally suited to the outdoor market.

To understand how hollow fibers work, think of a straw with permeable walls. Water is forced through the walls (filtered) and clean water flows out through the center channel. The real advantage comes when a cluster of hollow fiber straws is used, offering a dramatic increase in the amount of surface area available for filtration when compared with any other type of filter media. The benefits are much higher flow rates and a far lighter, more compact system.

How effective are hollow fibers?

Our system meets the EPA Guide Standard for the Removal of Bacteria and Protozoa. The pore size of the media is 0.2 microns.

The prefilter on my HyperFlow won’t lie flat. What can I do?

This can happen from tightly winding the hose around your filter for storage. To get the twists out of the hose, simply pull straight out to stretch it. You can also pinch the hose at one end and slide your fingers all the way down to the other end, allowing any coils to unwind on the way.

Why Backflush?

You must backflush regularly to maintain optimal performance of the filter cartridge. This is especially true in murky or very silty water. Since hollow fiber is not a depth-based media like ceramics, you don’t clean by removing clogged material from the exterior of the filter media. Instead, you must rinse the particulate that collects on the outside of the Hollow Fiber membranes. Infrequent backflushing makes the particulate harder to remove and more difficult to restore the media’s flow capacity. We recommend backflushing anywhere from every 8 liters to after each use, depending on water quality. The more you backflush, the better your flow performance and the longer life you can expect from your filter cartridge.

How do I backflush?

Click here for a video demonstration. Before leaving for the field give it a couple practice runs at home.

If you do air lock the filter cartridge, you will just need to reverse the check valves to their forward flow orientation, and pump water forward through the pump a couple of times. You have not damaged the fibers by air locking the filter.

I am having trouble backflushing. I pull back on the pump and no water comes through into the pump cylinder.

The most common problem with backflushing is getting air-lock in the filter cartridge. This can be avoided by ensuring that there is ONLY water (no air) present at the Pump Outlet. Read through the instructions for backflushing and check out the instructional video for assistance.

My filter clogged very quickly in the silty water I’m filtering. Is there anything I can do to extend the life of my filter?

Silty Water

Filtering very silty water can shorten the life of any filter. Here are some pointers to help minimize the effect of silt on your HyperFlow™:

  • Collect water in a pot or other vessel and allow the silt to settle out prior to filtering.
  • Strain water with a bandana or large coffee filter prior to filtering.
  • Use the Sweetwater® SiltStopper™ prefilter in conjunction with the pump. This will help trap silt particles before they hit the biological microfilter. This will reduce flow rates, but help prolong the life of your cartridge in challenging environments. (We recently updated the SiltStopper prefilter to accommodate the larger tube size of the HyperFlow microfilter. Earlier versions may need a zip tie to make sure the tubing stays attached firmly.)
Tea-colored (Tannic) water

This color of water typically comes from a high concentration of decaying vegetation adjacent to, or in, streams and lakes, resulting in a variety of organic acids. These include, but are not limited to, tannic, fulvic, and humic acids. These acids and the accompanying water conditions are very hard on ALL types of water filters.

Get your water elsewhere if you can. However, if no alternative exists and you are predominantly filtering these waters, we recommend using an MSR® MiniWorks® EX filter. Its ceramic element will collect all these impurities in its outer-most layer, allowing you to scrub away the clogged portion to restore normal flow rates. If you must use a HyperFlow filter, backflushing frequently will help to minimize the effect of these impurities. When you return home, add 2 drops of unscented household bleach to one liter of water and backflush this solution through the filter. This will help to break up organics that might be clogging the filter and provide the recommended treatment of your system for long-term storage.

Limited use in these conditions will not have a dramatic effect, but extended use can permanently impair hollow fiber media.

I’ve heard there were issues with some early versions of the HyperFlow. Have they been resolved?

In early 2008, we identified a flow performance issue with some of the first hollow fiber filter cartridges shipped with MSR HyperFlow microfilters. The performance issue did not affect the product’s ability to filter safe drinking water but could be frustrating, as the flow rate of some filters did not perform to product specifications. We have rectified the issue and all HyperFlow filter cartridges produced after January 2008 perform to flow specifications.

Are there any long-term storage recommendations?

When storing your filter for extended periods– essentially any time longer than two weeks, we recommend mixing 2 drops of household bleach (no fragrances or dyes) with 1 liter of water and pumping this mixture through the filter. This will help prevent the formation of biofilm (algae growth) which will reduce flow rates. Do not use more than recommended amounts of bleach. High levels of bleach can damage fibers.

What about freezing?

Once you have used your HyperFlow and wet the Hollow Fiber filter media, the fibers will remain wet for a very long time. Therefore, it is important to prevent it from freezing which can permanently damage the filter media. If you are traveling in areas where you are expecting freezing or near freezing temperatures, bring the filter into your tent - or even your sleeping bag if freezing is a definite concern. The Cleanside cover is watertight and will prevent any leakage wherever you store it. If you think your filter may be damaged from freezing, perform a Filter Test before the next use.

What if the filter takes a hard drop?

The casing of the pump is designed to protect the Filter Cartridge from most drops, but direct drops onto cement (or similarly hard surfaces) and any drops above 4 feet (1.2 m) should be avoided. If a Filter Cartridge outside the pump housing is ever dropped after being wetted, you should replace the Filter Cartridge. (We don’t recommend removing the Filter Cartridge from the protective pump housing except to replace the Filter Cartridge.) If you think your filter may have been damaged from a drop, perform a Filter Test before the next use.

Can I tell if I’ve damaged the hollow fibers?

Yes, you can, but not just by looking at the Filter Cartridge. If you have experienced a hard drop or may be concerned that your pump has frozen, there is a Filter Test Guide that came with your system. This includes instructions for checking the integrity of your filter. Also, please view this informational video about checking filter integrity. Essentially you’ll be intentionally air-locking your filter to prove the integrity of the hollow fibers. In preparation you need to make sure that your filter is fully wetted out. This means that you should have pumped several liters of water before performing this test. Generally your filter cartridge will not dry much during storage, so as long as you have used the pump a few times, you should be in good shape.

Is there a manual I can download for my HyperFlow microfilter?


How Do I Get Replacement Salt & Test Strips For My MIOX® Purifier?

Keeping your MIOX® purifier running strong is easy. Because the MIOX uses simple rock salt, and chlorine test strips that can be purchased off the shelf, we’re no longer asking you to rely on our customer service department for these replenishment supplies. Here’s what we’ve tested and recommend:

  • Salt: Food-grade rock salt or coarse salt (the type used in a salt grinder). This can easily be purchased at any grocery or kitchen supply store.
  • Test Strips: Off-the-shelf “Free Chlorine” test strips. You’ll want ones that register free chlorine levels of 3.0 ppm. We recommend SenSafe™ Free Chlorine Water Check test strips.
  • Using the Test Strips: Follow the instructions in your MIOX users’ manual, substituting the off-the-shelf test strips for Step 8 and Step 10 in the illustrated instructions (or Step K and Step L in the written instructions).

Greater than or equal to 3.0 ppm free chlorine = OK. Less than 3.0 ppm free chlorine = Too Low.

See MIOX instructions here.

What are the metal parts that I see when looking into the open purifier?

The metal parts make up the electrolytic cell. When you look down into the top of the purifier you will see a 3/8" diameter titanium post in the center; this is the cathode. Around the inside of the cell, inside the plastic outer case, is a piece of titanium tubing; this is the anode. The anode and the cathode are the two halves of the electrical circuit that create the MIOX cocktail.

How do I decide if the MIOX Purifier is the best choice for me?

The MIOX Purifier is ideal for anyone who needs their water treatment system to:

  • Purify (not just filter) for international travel and heavily used backcountry areas.
  • Treat very large quantities of water without pumping.
  • Be ultralight and ultra-compact.
  • Be virtually maintenance free.
  • Positive, visual confirmation that dosing is adequate to purify.

For example, a large group on a river trip can gather water in gallon containers at night, dose with the MIOX Purifier in minutes, and have purified water ready to go in the morning. The MIOX Purifier has a 7–10-year shelf life due to its lithium batteries, making it ideal for emergency preparedness and is compact and light enough for ultralight travel.

Using the MIOX Purifier in conjunction with a filter is an excellent system for international travel. Purifying pre-filtered water with a MIOX solution reduces dwell times to only 15 minutes by removing resistant protozoa and is an excellent strategy for extremely challenging water, greatly improving dirty-tasting or -smelling water. The MIOX Purifier also provides peace-of-mind. It is the only chemical purifier with safety-indicator strips to confirm that you have added enough disinfectant to purify your water after the appropriate dwell time.

How do you know the MIOX Purifier inactivates giardia, cryptosporidia, bacteria, and viruses, and how long does it take?

Two full rounds of testing according to the Environmental Protection Agency Guide Standard were performed at BioVir, an independent lab, using the MIOX Purifier. One test was performed with giardia plus bacteria and viruses in both general (type 1) and worst-case (type 2) water as per the EPA Guide Standard. Knowing that cryptosporidia is a more resistant bug, testing was also performed with crypto plus bacteria and viruses in both waters. The required 3-log inactivation was achieved in both general and worst-case water conditions in 30 minutes for giardia and four hours for cryptosporidia. Bacteria and viruses were inactivated to the required 6-log and 4-log levels in only 15 minutes for both water types.

What is cryptosporidia?

According to the United Stated Center for Disease Control, “Cryptosporidiosis is a diarrheal disease caused by microscopic parasites of the genus Cryptosporidium. Both the disease and the parasite are commonly known as "Crypto."

Many species of Cryptosporidium exist that infect humans and a wide range of animals. The parasite is protected by an outer shell that allows it to survive outside the body for long periods of time and makes it very resistant to chlorine disinfection.

While this parasite can be transmitted in several different ways, water is a common method of transmission and Cryptosporidium is one of the most frequent causes of waterborne disease (drinking water and recreational water) among humans in the United States.”

Because both animals and humans carry crypto, it is found in most surface water sources. The potential for contamination can be estimated by the surrounding influences, such as agricultural operations, high concentrations of wildlife and/or well-traveled backcountry areas where improper human waste disposal has become problematic.

If I run out of salt, can I use any salt or seawater?

Other forms of salt besides rock salt will work, including table salt, sea salt, crystal salt, tablet salt, and even No Salt, which is a potassium chloride mixture. Seawater is not salty enough to work and will give a low-salt fault if used. If you use table salt, you may need to shake more vigorously because of the compaction that occurs with small granules, and you may need to shake more than 10 times to get the right concentration of brine.

What oxidants does the MIOX Purifier make and how does it make them?

Electrolysis breaks the chemical bonds of the salt water, or brine (NaCl + H2O), and stimulates chemical reactions, creating primarily chlorine (Cl2 + HOCl + OCl-). Based on microbiological testing, it is likely that other chloroxygen compounds more potent than chlorine are also being created. With current technology, we have been unable to identify these other compounds; therefore, we can claim only that we make a strong chlorine/hypochlorous acid solution. We know, however, that the MIOX solution effectively inactivates cryptosporidia, while chlorine does not—even after days of exposure. The bubbles you see while the purifier is operating are hydrogen ions being freed.

How does the MIOX cocktail compare to chlorine dioxide, chlorine, and iodine treatment?

The MIOX cocktail and chlorine dioxide tablets are effective against cryptosporidia, while chlorine and iodine are not. The MIOX Purifier performs as well as the chlorine dioxide tablets on the market and has the added benefit of an unlimited self life (other than the batteries which must be replaced every 7–10 years). Chlorine dioxide tablets expire after two years. Also, MIOX-treated water tastes better than water treated with iodine, does not make the treated water urine-colored, and does not have the possible thyroid side effects of iodine. In addition, the MIOX Purifier is the only chemical treatment technology with safety-indicator strips for solid confirmation that you have added enough disinfectant to purify your water after the appropriate dwell time. The main reason someone would choose tablets over the MIOX Purifier is cost. However, after 200 liters of operation, or one set of lithium batteries, you will break even with the cost of using comparable tablets and then the MIOX Purifier will start paying for itself.

How long do the salt and batteries last?

The salt packet and batteries provided will last for about 200 liters of operation depending on use. Doses for larger volumes will deplete the batteries faster than those for smaller volumes, with the four-liter treatments causing the most depletion. A full salt chamber will treat about 20 liters depending on use.

How do I treat more than four-liter volumes of water?

To treat volumes greater than four liters, simply calculate how many doses are needed to total the desired volume and add the doses one after the other. For example, if you have 10 liters of water to treat, add two four-liter doses and one two-liter dose. To determine if the proper dosing has been achieved, be sure to check with the safety-indicator strips according to the directions, after the last dose is added.

What about taste—does it make good coffee?

Under most conditions, you will not notice any unpleasant taste. However, some people report a slight tap-water flavor. In tea-colored/tannic water with high organic content, it is possible to detect a more noticeable flavor as the oxidants react with the tannic acid. For those with a sensitive palate, adding vitamin C (ascorbic acid) and drink mixes after the required dwell time can improve taste. In addition, exposure to sunlight and aerating the water after the required treatment time will help improve taste. MIOX®-treated water will also impart a strange taste if used for making coffee. However, boiling water itself is an effective method of purification so there is no need to brew your coffee with Miox-treated water.

What is background demand?

Background demand refers to how much of the oxidant or disinfectant is used up by the background impurities in a given source such as silt, organic matter and dissolved solids. For example, a fast-running clear mountain spring in the heart of the Cascades will have a small background demand, mostly from dissolved solids, while a molasses-paced, tea-colored river channel in the Everglades will have a much higher demand from decaying organic matter and the unfortunate runoff from encroaching developments. The greater the background demand, the more disinfectant needed for effective purification. The MIOX Purifier will create enough disinfectant in one dose to treat the majority of water sources in the U.S. However, when traveling to developing countries or using a highly suspect water source, a second dose may be needed.

Since water sources vary, how do I know I've added enough MIOX cocktail?

After you have dosed your water with the appropriate level of cocktail, check it with the included safety-indicator strips. Remove one safety-indicator strip from the bottle and swirl the end with the pad in the treated water for one second. After 15 seconds, compare the color of the pad to the color chart on the bottle to determine if the water has been treated with enough MIOX cocktail. The color should match or be darker than the color block next to the "OK" reading. If it is, wait 10 minutes and repeat the check one more time. If both readings are OK, wait the required dwell time before drinking. If the reading is TOO LOW at either reading, repeat the dosing procedure and recheck with another safety-indicator strip until you achieve an OK or OK+ reading.

What if I don't have the safety-indicator strips?

Don't panic. We have an overkill option just for this purpose. Simply add two four-liter doses per liter of water, shake and wait the required treatment time.

If the water is cold, do I have to wait longer?

No, you do not have to wait longer when your water source is cold. The wait times listed are for use in worst-case water conditions, which include a temperature of 40 degrees Fahrenheit (4 degrees Celsius).

What about that scum (bio-film) in my container?

Tests performed on municipal systems during the switch from chlorine to MIOX treatment show that mixed oxidants are superior for bio-film removal. So the scum should disappear with the use of the MIOX Purifier.

Does the MIOX Purifier cocktail reduce chemical contaminants or heavy metals?

The MIOX Purifier was created with the military in mind. One of the main concerns for military personnel are chemical weapons. Many of the chemical weapons are beefed-up versions of pesticides and herbicides, which are often used as surrogates in testing. The U.S. Dugway Proving Ground performed testing on the MIOX Purifier to determine its efficacy against chemical contaminants. It is very effective at reducing the chemical weapons Soman, VX, and Lewisite. Environmental Health Labs performed testing using the MIOX Purifier to determine efficacy against pesticides, herbicides, and VOCs, and it performed well with complex open-structured compounds such as Malathion but not with simple closed-structured compounds such as Benzene. The MIOX Purifier is not effective at reducing heavy metal contamination. In general, it is best to avoid water sources such as mining tailing ponds or those near large agricultural operations.

I make it a point to consume antioxidants. Is there a problem adding oxidants to my water?

Much of what we do in life contains some level of risk. Many feel that the benefits of disinfecting water greatly outweigh the risks. However, if the residual disinfectant is of great concern, a one-micron filter containing carbon can be used 15 minutes after treatment with the MIOX Purifier to remove any residual oxidants from the water. It is also a very effective way to treat really nasty water. Some people choose not to use chemical treatment at all, which is not usually a problem here in the U.S. In developing countries, however, where there is a high risk of human waste contamination, and therefore a concern of viral contamination, a chemical treatment step can save you from the viral two-step.

I am sensitive to chemicals in water—is the MIOX Purifier the right choice for me?

People sensitive to chemicals, or those who would prefer to avoid them altogether, can use boiling as another option for effective water purification. While some might think UV purification is an effective option, it is extremely difficult to inactivate Cryptosporidium in this manner – especially in silty water or in volumes of over 1 liter at a time.

I am on a salt-restricted diet. Will the salt in the MIOX solution be a problem?

Approximately 5–50 milligrams/liter of sodium is added, depending on the dosage. Sodium addition is less pronounced at higher treatment volumes because the mixed oxidants are more concentrated at those levels. Two ways to minimize sodium addition are to shake the purifier fewer times, resulting in a less concentrated brine solution, and/or to use the four-liter dose.

What about disinfection by-products?

Since chlorine and hypochlorous acid are present in the MIOX cocktail, disinfection by-products can be formed. For added protection, use a one-micron filter containing carbon 15 minutes after treatment with the MIOX Purifier to remove disinfection by-products.

Will the MIOX solution damage my gear if spillage occurs?

Since the MIOX cocktail contains chlorine and can discolor or damage fabrics, we recommend you use caution when creating and using it.

I dropped my MIOX Purifier and now it won't work—what's wrong?

On some early models of the MIOX Purifier the battery bumper was not cushy enough to withstand a direct three-foot drop on concrete that directly impacted the battery cap. This can cause a dent in the batteries to the degree that they no longer touch the contact strip. A new set of batteries will fix the problem.

I am treating tea-colored water and my MIOX Purifier isn't working properly—what's wrong?

Some waters, such as swamps and bogs, contain high levels of organics making them tea-colored. The organics in the water react with the salt while creating the saltwater solution, or brine. Water sources with high organic content require more shaking to achieve the required levels of salt in solution to run the MIOX Purifier. Some waters require as many as 50 shakes. In this case a smaller dose will run better than the larger four-liter dose. Another fix is to have a small container of water that does not contain high levels of organics to use for making the MIOX cocktail.

Can I use a filter with the MIOX purifier to decrease the treatment time?

Yes, if a one-micron filter or smaller is used then you only need to wait 15 minutes for inactivation of viruses and/or bacteria. The MIOX treatment can be added either before or after filtration. If added before filtration, wait 15 minutes before filtering and be sure to filter into a clean container. If added after filtration, wait 15 minutes before drinking the water.

Can I use rechargeable batteries in the MIOX®?

While it is possible to find some rechargeable batteries that can power the MIOX, in general they are quite unreliable due to inconsistencies in manufacturer’s power output ratings. In addition, because they tend to die with little warning and drain over time without use, we recommend using only CR123 Lithium batteries to ensure reliable performance.

Is there a manual I can download for my MIOX purifier?

MiniWorks EX / WaterWorks EX FAQ

Can I upgrade my old MiniWorks with an EX filter?

Marathon™ EX ceramic cartridges are compatible with all WaterWorks and MiniWorks microfilters, old and new. Using it in a pre-2003 filter will increase a MiniWorks filter's output by approximately 25%, thanks to the new AirSpring Accumulator™.

What are the materials in the EX filters?

The Marathon ceramic element is made from diatomaceous earth that's heated to the point where it just begins to melt. Most particles are caught within about .005 inch of the surface. When it clogs, you abrade away the clogged pores, making them immediately ready for more use, with almost 100% recovery after each cleaning. Marathon ceramic provides long-lasting protection from protozoa and bacteria. A block carbon core reduces tastes, odors, some chemicals, and many pesticides. The WaterWorks microfilter also incorporates a PES (polyethersulfone) membrane filter, which passes the test for a sterilizing or pharmaceutical-grade filter. It serves as a safety net, providing a second fail-safe seal.

How long will my ceramic filter last?

How long a filter lasts will vary radically from one water source to the next. The ceramic element can last up to 2000 liters. Filter-life ratings are based on best-case scenarios because the testing is performed with clean lab water. Generally you can assume that your filter will last between 50 and 100% of the rated life.

How much water will my filter pump before clogging?

Normal conditions may allow a user to filter between 10 and 20 liters between cleaning. Please note that water quality varies a lot with the season and water source. In general, the more turbid (cloudy) the water, the more frequently your filter will require cleaning and eventually replacement. The MiniWorks is one of the most cost-effective portable treatment devices currently available.

Why is the handle on my filter so hard to push?

There are three possible causes of this. The most likely is that one of the microfilters is clogged. Review the instructions for cleaning the ceramic filter. The PES membrane (WaterWorks microfilter only) may also be clogged. It will have to be replaced or removed altogether. Lastly, the piston O-ring may be very dry, causing friction. Lubricate it with the silicone lubricant provided in the maintenance kit (or use lip balm or petroleum jelly).

Why is the handle on my water filter so hard to pull?

If the handle is hard to pull, something is obstructing the flow of water into the filter. Clean the inlet foam and remove any kinks in the inlet hose.

Why does the handle on my filter feel limp when pumping?

The most common reason for a limp handle is dirt under the umbrella valve. Remove the head of your water filter to expose the umbrella valve. Rinse under it or pull it off and rinse. Reinstall.

Why does my filter squeak when I am pumping?

The squeaking you hear is probably caused by actuation of the pressure-relief valve. This valve is designed to release when there is excessive pressure. Water goes back out the intake hose so you stay dry. You can tell if your relief valve is releasing by watching bubbles in the intake hose—if they go back and forth when you pump, the relief valve is working. It may be time to clean your ceramic filter (reference your owner's manual for complete details), or maybe you are pumping too fast. Do not pump faster than one stroke per second for best efficiency. Older MSR filters sometimes squeak in the pump head, piston pins, and bushings. You can eliminate the squeak with a tiny dab of lubricant on these parts. Newer MSR filters have the lubricant molded right into the pins and bushings, eliminating the squeak.

How should I store my EX filters?

Remove the ceramic element and air dry for 3–5 days. This will prevent growth of mold, mildew, and bacteria. Wash and dry other filter parts thoroughly before long-term storage

I forgot to dry out my filter before putting it away—what should I do now?

The ceramic cartridge, which comes as standard equipment in the WaterWorks and MiniWorks, can be boiled to kill bacteria that may grow in it. Always let the water cool down before removing the ceramic cartridge from the water. Removing it early can damage the plastic end caps. (Cold water can be added to the hot water to speed this process.) Dry thoroughly before storing. FYI: Because the WaterWorks microfilter has a bacteria-proof membrane immediately downstream from the ceramic cartridge, bacteria cannot get into the water you drink even if it grows in the ceramic.

What happens if my filter freezes?

If you anticipate that you will encounter freezing temperatures, make sure you drain the filter of excess water after each use to protect it from damage. If the filter does freeze, bring it inside the tent or other warm place to thaw, or follow the directions (in the instructions) for boiling the cartridge.

Can I use the Sweetwater® Purifier Solution with the MiniWorks?

Unfortunately, no. The SweetWater Purifier System and Solution are regulated by the EPA and have undergone extensive laboratory testing to verify their efficacy as a system. SweetWater Purifier Solution is carefully formulated to inactivate viruses remaining in water that has been pumped through a SweetWater Microfilter. Filters vary in performance and it is likely that more or less disinfectant may be required to achieve purification with other filters. Along the same lines, for the solution to work independently of a filter, you would need a very strong dose—to the point of tasting offensive. The wait time would also be much longer than five minutes. Finally, cryptosporidia, which would have been removed by the filter, would not be effectively inactivated by use of the SweetWater Purifier Solution alone.

Is there a manual I can download for my MiniWorks EX microfilter?

SweetWater FAQ

How does the system work?

First, pump with your SweetWater microfilter. This will take care of giardia, crypto, bacteria, and particulates. Next, add five drops per liter of SweetWater Purifier Solution, shake and wait five minutes. This will inactivate viruses and leave you good-tasting, purified water.

When do I need SweetWater Purifier Solution?

Whenever there is a possibility of human waste contaminating the water. Definitely when visiting developing countries and also in high-use areas of developed countries, such as the Appalachian Trail, where recent outbreaks of the Norwalk virus have been reported.

What is SweetWater Purifier Solution?

SweetWater Purifier Solution is an EPA-registered grade of bleach, which we have formulated to prolong shelf life to two years. The technical term for the active ingredient in bleach is sodium hypochlorite. The common industry name is chlorine. Chlorine is the disinfectant of choice used in the treatment of tap water. So it's a tried-and-true method and thus tastes familiar. In our taste-testing only two out of 10 people reported a tap-water taste; the other 8 detected no chlorine flavor. For those with especially discerning taste buds, vitamin C (ascorbic acid) or drink mixes can be added after the five-minute wait time to reduce any chlorine flavor that remains.

Why can't I use SweetWater Purifier Solution with other filters or by itself?

The SweetWater Purifier System and Solution are regulated by the EPA and have undergone extensive laboratory testing to verify their efficacy as a system. SweetWater Purifier Solution is carefully formulated to inactivate viruses remaining in water that's been pumped through a SweetWater Microfilter. Filters vary in performance. It is likely that more disinfectant may be required to achieve purification with other filters. Along the same lines, for the solution to work independently of a filter, you would need a very strong dose—to the point of tasting offensive. The wait time would also be much longer than five minutes. And finally, cryptosporidia, which would have been removed by the filter, would not be effectively inactivated by use of the SweetWater Purifier Solution alone.

Why not use iodine tablets?

Iodine tablets are costly, at 80 cents a gallon, have a short shelf life, and, since they taste unpleasant, contribute to dehydration. More importantly, scientific tests have proven them to be ineffective against cryptosporidia, while double doses and long dwell times are required to eliminate giardia. Also, chlorine, unlike iodine, is not use-restricted. It can be used-long term and while pregnant. Finally, there are no confusing instructions based on water conditions. With the SweetWater Purifier System you pump only once, as fast as you like, add five drops/liter of SweetWater Purifier Solution, shake, and wait only five minutes under all conditions. No double pumping and no long wait time.

Why is SweetWater Purifier Solution added after filtration?

When developing the system, both pre- and post-treatment methods were tested. We found that post-treatment was the simplest, the most effective, and the best way to minimize the amount of chemical used in the water. This is because filtration removes a majority of the contaminants from the water, which allows the chlorine to react only with the viruses. Therefore, much less chlorine is needed and you don't have to have to worry about water conditions.

What about leakage of SweetWater Purifier Solution?

SweetWater Purifier Solution is packaged in a durable dropper bottle with a tight-sealing screw cap, then enclosed in a zip-lock baggy. This offers double protection from leakage. Since it is a chlorine solution and can discolor or damage fabrics, we recommend you use caution when packing and keep it in the supplied zip-lock bag when not in use.

How should I store SweetWater Purifier Solution?

In order to avoid deterioration, store your SweetWater Purifier Solution in a cool, dry area, away from direct sunlight and heat. For even better results, refrigerate when not in use. The two-year shelf life was based on an average temperature of the solution at 77° F/25° C. To counterbalance any high-temperature exposure, it is a good idea to store the product in the refrigerator when not in use.

What is the filter material in the SweetWater Microfilter?

The labyrinth depth filter is made of a proprietary blend of microscopic borosilicate fibers in a specially formulated binder resin. A black (or white) mesh filter-replacement safety indicator is imbedded in the filter to let the user know when to purchase a new cartridge. Lastly, there is granular activated carbon to reduce unpleasant tastes and odors.

How long will my filter last?

Filter life varies greatly depending on water source. The SweetWater Microfilter is rated up to 750 liters. Filter-life ratings are based on best-case scenarios because the testing is performed with clean lab water. Generally you can assume that your filter will last between 50 and 100% of the rated life.

What if normal cleaning doesn't restore flow?

If regular brushing does not help to fully restore flow rate, the Sweetwater filter cartridge may be clogged with organic matter. Mix up a bleach solution of 30 milliliters (1 ounce, or 2 tablespoons) of regular household bleach to 1 liter (1 quart) of water. Pump the solution through the filter, stopping before pumping air in to the inlet tube, and allow the filter to soak (assembled) overnight. The next morning, pump a couple of liters through. Now the filter is clean and ready for your next trip.

Why is my SweetWater Microfilter becoming more and more difficult to pump?

The more that you have used the filter, the slower you will be able to pump water. Also, it is normal that, with use, the flow rate will slow from its initial rate of 1+ liters per minute. With these points in mind, when pump resistance grows, first clean the filter, then back flush the SiltStopper prefilter (if included). Make sure that the bottle adapter air hole is clear, and confirm that the hoses are not kinked. If these actions do not lessen resistance (especially the cleaning), then it's most likely time to replace the filter.

How should I store my filter?

Remove inlet hose from the water source and pump SweetWater Microfilter until dry. Detach the filter cartridge from pump and shake out water; air dry if possible. Avoid getting unfiltered water into outlet hose or bottle adapter. For long-term storage, place filter cartridge in a zip-lock bag in freezer to retard bacterial growth. Discard your first few quarts of water filtered after extended storage.

What if I forgot to follow the storage directions for my SweetWater Microfilter?

No problem. If the filter is dry and clean, pump a couple of liters through it and you're good to go. If the filter is wet and scummy, mix up a bleach solution of 30 milliliters (1 ounce, or 2 tablespoons) of regular household bleach to 1 liter (1 quart) of water. Pump the solution through the filter, stopping before pumping air in to the inlet tube, and allow the filter to soak (assembled) overnight. The next morning, pump a couple of liters through and you're ready for your trip. This is also an excellent way to rejuvenate a filter that is not responding well to brushing. If you did follow the storage instructions, be sure to thaw out your filter cartridge overnight and pump a couple of liters through it to make sure everything is in working order before your trip.

How do I use the SiltStopper® prefilter?

Attach inlet or dirty hose of the microfilter to the red hose barb at the bottom of the SiltStopper prefilter. Attach one end of the short clear hose provided with the SiltStopper to the clear hose barb at the top of the SiltStopper. Finally, attach the other end of the short hose to the inlet hose barb of the microfilter.

Is there a manual I can download for my SweetWater microfilter?

MSR Hydration FAQ

How do I dry my MSR reservoir?

MSR reservoirs are easily dried. Prop them open with a spoon or other utensil to let them air dry. Alternately, hang them on a plastic bag dryer, widely available at kitchen supply stores and numerous online retailers.

How do I freeze my MSR reservoir?

A frozen reservoir makes a great ice pack and, during the dog days of summer, delivers a steady source of cold, refreshing hydration. Lay your reservoir half-full on its side in the freezer with all air purged. Do not over-fill. Water expands as it freezes and this can burst your reservoir.

How do I clean my MSR reservoir?

Use hot, soapy water and rinse thoroughly with hot water. For tough cleaning jobs, add 1/4 cup of baking soda to 3/4 cup of water per liter and shake for 30 seconds. Add 1/4 cup lemon juice and wait a moment for the effervescence to subside. Shake 10 seconds and vent by loosening cap away from face. Repeat shaking and venting three times. Expel as much air as possible, cap bottle, and allow to soak 20 minutes. Rinse thoroughly with hot water. Caution: When adding lemon juice to baking soda, effervescence occurs and will cause pressure to build inside your reservoir. Vent often.

How do I disinfect my MSR reservoir?

To disinfect, add one ounce of unscented household bleach (such as Clorox Regular or Clorox Ultra) to one liter of clean water. Mix for 10 seconds. Fill drinking tube with solution and leave overnight. Rinse thoroughly and air dry.

My bite valve comes off too easily. What should I do?

The best way to restore a snug fit between the bite valve and the drinking tube is to remove the bite valve from the drinking tube. Next, cut a small section off the end of the drinking tube. Clean the bite valve and drink tube with rubbing alcohol, lick the end of the drinking tube and place the bite valve back on the end. After it dries, there should be an excellent seal.

How do I prevent the water in my hydration system from freezing in cold weather?

Start the day with warm or hot water in your reservoir and pack any extra clothing layers around it. Inside a pack, this will generally prevent freezing in all but the most extreme cold. For drink tubes and bite valves, sip often to maintain flow. Do not leave residual water in the drink tube between drinks. Blow into your bite valve to force water back into the reservoir. Also, keep as much of the drink tube covered as possible; inside a pack or jacket.

Is there a way to filter into my reservoir without removing it from my pack?

Yes. Simply remove your bite valve and connect the end of your hose directly to your filtration system’s outflow port. This method is compatible with all MSR® filters. Using an AutoFlow™ filter system, this method creates one of the lightest, most compact and efficient means possible of getting water.

My water sloshes around in my reservoir when riding or running. Can I make it stop?

Absolutely. Simply turn your reservoir upside down after filling it. Then simultaneously squeeze the reservoir and the bite valve to purge all the air. This will eliminate sloshing.


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