Best portable water filters for emergencies

Four portable filters and purifiers, compared on what their makers publish. We have not tested them. First, what the CDC says a portable filter can and cannot do.

Specifications last checked November 9, 2026. How we evaluate · Corrections and updates

For a household or group, see the gravity filters guide.

Start with stored water and boiling

Ready.gov says to store at least one gallon of water per person per day for several days, for drinking and sanitation. Water that is not commercially bottled should be replaced every six months. A filter is for when that supply runs out.

The CDC calls boiling the best way to kill germs in water: a rolling boil for 1 minute, or 3 minutes above 6,500 feet. If you can boil, you do not need a filter for germs. A filter helps when you cannot boil, or as a first step for cloudy water.

What a portable filter can and cannot do

The CDC's guidance on making water safe in an emergency sets three limits:

• Viruses. Portable filters will not remove viruses. After filtering, the CDC says to add a disinfectant such as chlorine, iodine or chlorine dioxide.
• Pore size. To remove bacteria, a filter needs an absolute pore size of 0.3 micron or smaller. For parasites such as Giardia or Cryptosporidium, 1 micron or smaller.
• Chemicals. Water with fuel or toxic chemicals cannot be made safe by boiling or disinfecting. Use bottled water or another source.

Three of the four products below list pores of 0.1 or 0.2 micron, which meets the CDC's size rule for bacteria and parasites. They do not claim to remove viruses. The fourth, the Grayl GeoPress, is sold as a purifier and says it removes viruses. That is the maker's claim, and we have not seen the lab report. Grayl also says an independent lab tested it to NSF/ANSI protocols 42 and 53.

Quick answer

These are comparisons of published figures. A household facing flood or sewage water could reasonably choose differently from one facing a short outage.

The four models, one by one

Sawyer Squeeze

The Squeeze has a 0.1 micron hollow-fiber membrane and comes with two reusable pouches, a cleaning plunger and coupling, and gravity tubing. Sawyer says it removes 99.99999% of bacteria and 99.9999% of protozoa, citing an independent lab report. The filter weighs about 3 oz, and the full kit lists 8.19 oz. It is covered by a lifetime limited warranty, but Sawyer says a filter can be backwashed to restore up to 98% of its original flow. It also says there is no warranty for a frozen filter and recommends replacing one you suspect froze after first use. Its help page says it will not remove metals, chemicals, pesticides, VOCs or salt. Sawyer does not claim virus removal.

LifeStraw Peak Series Straw

It uses a 0.2 micron membrane, weighs 2.3 oz (65 g) and is rated for 4,000 L (1,000 gal). LifeStraw says it meets US EPA and NSF P231 standards for removing bacteria and parasites, and its warranty is 3 years. It does not claim virus removal.

Katadyn BeFree 1.0L

The BeFree 1.0L Black Edition is a collapsible 1-liter flask with a 0.1 micron filter that removes bacteria, cysts and sediment. It weighs 73 g, with a flow of up to 2 liters a minute and a capacity of up to 1,000 L depending on water quality, for clear water. Katadyn describes it as suited to occasional use. Katadyn's warranty statement gives 2 years for its filters other than the Pocket. A different model, the BeFree AC, adds a carbon stage and is a separate product.

Grayl GeoPress 24 oz

The GeoPress is a press bottle that makes 24 fl oz in 8 to 10 seconds, at up to 5 liters a minute. Grayl rates the cartridge for 350 presses (250 L, 65 gal) and says it removes viruses, bacteria and protozoan cysts. That is 250 L, against 4,000 L for the LifeStraw. The cartridge carries a 10-year warranty for workmanship. Grayl says an independent lab tested it to meet or exceed NSF/ANSI protocols 42 and 53, and that it meets the EPA's guide standard for purifiers. At 15.9 oz (450 g) it is by far the heaviest of the four. The product page gives no removal percentages, so we leave those blank.

How to choose

• Match the filter to the threat. For clear lake or stream water, a 0.1 or 0.2 micron filter covers bacteria and parasites. For water that may carry sewage or flood runoff, viruses are a concern, so a purifier claim or a disinfectant step matters.
• Pre-filter cloudy water. The CDC says to strain it through a clean cloth or coffee filter, or let it settle, before treating.
• Check cleaning and storage. Sawyer, for one, voids its warranty on a frozen filter. Read the maker's manual for both, and try the filter once before you need it.
• Price. Prices change often, so we do not print them here. Compare the current price on the seller's page.

Safety and limits

• Follow the maker's instructions. The figures here are the makers' claims, not our test results.
• Chemical contamination. None of these products makes fuel- or chemical-contaminated water safe. Use bottled water.
• No promise of protection. We compare published figures. We do not promise that any product will protect your health.

Questions people ask

Is a filter the same as a purifier?

No. The CDC says portable filters do not remove viruses. A purifier is sold with a virus-removal claim, as Grayl does for the GeoPress.

Do I need a filter if I can boil water?

No. The CDC calls boiling the best way to kill germs. A filter is useful when you cannot boil, and for cloudy water before you boil it.

All four, side by side

Cells marked "to be verified" are figures we did not find on the maker's page. We leave them blank rather than guess.

Where the figures come from

• CDC: How to Make Water Safe in an Emergency
• Ready.gov: Water
• Sawyer Squeeze, product page, help page and Sawyer Standard page
• Katadyn warranty statement
• LifeStraw Peak Series Straw, product page and warranty page
• Katadyn BeFree 1.0L Black Edition, product page
• Grayl GeoPress 24 oz, product page

Citing the CDC and Ready.gov does not mean they endorse this site. If a figure here is wrong, tell us. We fix it and note the change on the corrections page.