Frequently Asked Questions


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