Verdict: the Sawyer Squeeze (SP129) is the best all-round backup water filter for a home emergency kit. Sawyer rates it to 0.1 micron absolute and says it removes 99.99999% of bacteria and 99.9999% of protozoa. It does not claim to remove viruses, so plan to boil or disinfect after filtering. Choose the Platypus GravityWorks 4.0L to filter for a family without pumping, the MSR Guardian for virus protection at household volume, and the GRAYL GeoPress for a go-bag.

A filter is a backup, not your water supply. Stored water comes first (see the emergency water storage container guide ), and CDC says boiling is the best way to kill germs in water.

Filters, purifiers and what neither can fix

CDC’s water treatment guidance explains what portable devices can and can’t remove:

  • Filters remove parasites and, at an absolute pore size of 0.3 micron or smaller, bacteria too, but not viruses. CDC’s advice is to filter water and then disinfect the filtered water.
  • Purifiers go further: their makers rate them to remove viruses too. The MSR Guardian and GRAYL GeoPress below carry that claim.
  • Chemicals are a separate problem. CDC says you cannot make water containing fuel, toxic chemicals or radioactive materials safe by boiling or disinfecting it. Use bottled water or a different source, and contact your health department. Platypus and MSR list their units as not effective against chemicals or toxins.

CDC also warns never to use water from radiators or boilers that are part of a home heating system for drinking, cooking or hygiene.

Quick picks

Pick Best for Type Maker says it removes Flow (maker) Cartridge life (maker)
Sawyer Squeeze SP129 All-round backup Squeeze filter, 0.1 micron absolute Bacteria, protozoa, microplastics Not published Not published; lifetime limited warranty
Platypus GravityWorks 4.0L Filtering for a family Gravity filter, 0.2 micron Bacteria, protozoa Up to 1.75 L/min Up to 1,500 L
MSR Guardian Virus protection at volume Pump purifier, 0.02 micron Viruses, bacteria, protozoa 2.5 L/min 10,000+ L
GRAYL GeoPress 24 oz Go-bag purifier Press bottle purifier Viruses, bacteria, protozoan cysts 24 oz in as little as 8 seconds About 350 cycles (250 L)

Specifications are from each maker’s product page, checked October 5, 2026.

The picks

Sawyer Squeeze: best all-round backup filter

The Sawyer Squeeze (SP129) uses a 0.1-micron absolute hollow fiber membrane. Sawyer says it removes 99.99999% of bacteria such as salmonella, cholera and E. coli, 99.9999% of protozoa such as giardia and cryptosporidium, and 100% of microplastics. It is backed by Sawyer’s lifetime limited warranty.

It is the most flexible pick for a home kit. You fill the included pouch and squeeze water through the filter into a clean container, or thread the filter onto a standard bottle with 28 mm threads. Sawyer’s kit also includes gravity tubing, inline hydration pack adapters, a cleaning plunger and a cleaning coupling. Because it does not claim virus removal, follow CDC’s filter-then-disinfect approach.

Platypus GravityWorks 4.0L: best for filtering for a family

The Platypus GravityWorks 4.0L is a pump-free gravity system with a dirty reservoir, a clean reservoir, a hollow fiber microfilter, hoses and a shutoff clamp. You hang the dirty bag and let gravity do the work. Platypus lists a flow of up to 1.75 liters a minute, a 0.2-micron pore size, a cartridge life of up to 1,500 liters and a system weight of 11.5 ounces.

Platypus says every microfilter is individually tested to meet EPA and NSF guidelines for removing 99.9999% of bacteria and 99.9% of protozoa. Its spec table lists it as not effective against viruses or chemicals, so disinfect after filtering. Platypus recommends backflushing a quarter liter of water for every 6 liters filtered, depending on water quality.

MSR Guardian: best for virus protection at volume

The MSR Guardian is a hand-pump purifier with a 0.02-micron hollow fiber cartridge. MSR says it meets NSF protocol P248, the testing standard used by the U.S. military, for removing viruses, bacteria, protozoa and sediment. It pumps 2.5 liters a minute, and the cartridge treats 10,000+ liters.

MSR says the pump cleans itself on every stroke, so it never needs backflushing, and that it is built to withstand freezing and 6-foot drops to concrete. It weighs 1 lb 1 oz and measures 8.25 by 4.4 inches. Choose it if you want one device that removes viruses for a whole household without chemicals or waiting.

GRAYL GeoPress: best purifier for a go-bag

The GRAYL GeoPress 24 oz is a bottle with a press-down purifier cartridge. GRAYL says it removes 99.99% of viruses, 99.9999% of bacteria and 99.9% of protozoan cysts. It also says the cartridge meets the U.S. EPA’s Guide Standard and Protocol for testing microbiological water purifiers. It holds 24 oz (710 ml), weighs 15.9 oz, and makes a full bottle in as little as 8 seconds.

GRAYL rates the cartridge for about 350 cycles (250 liters). Replace it when a press takes about 25 seconds, or three years after first use. An unused, airtight cartridge can be stored for up to 10 years, which suits a bag that sits in a closet. GRAYL also says its activated carbon adsorbs chemicals including PFAS and VOCs, but CDC’s advice for water with fuel or toxic chemicals is still to use another source.

How to treat water after a disaster

Follow your health department’s instructions first. Beyond that, CDC and Ready.gov give these steps:

  • Boil when you can. Bring clear water to a rolling boil for 1 minute, or 3 minutes above 6,500 feet. Ready.gov calls boiling the safest method of treating water.
  • Settle or strain cloudy water first. Let particles settle, or strain the water through a clean cloth, paper towel or coffee filter. GRAYL notes that straining out silt also extends cartridge life.
  • Filter, then disinfect. For the Sawyer and Platypus filters, boil the filtered water or disinfect it with unscented household bleach.
  • Use bleach by the label. CDC says to follow the bleach label’s directions for disinfecting drinking water, stir, and let it stand at least 30 minutes.
  • Store treated water clean. Keep it in clean, sanitized containers with tight covers.

We left purification tablets off this list. CDC lists iodine and chlorine dioxide tablets as disinfectants, but Ready.gov says iodine and camping-store treatment products whose only active ingredient is not 5.25 to 6.0 percent sodium hypochlorite should not be used.

How to choose an emergency water filter

  • Decide whether you need virus removal. The Sawyer and Platypus filters do not claim it, so they rely on boiling or bleach afterward. The MSR Guardian and GRAYL GeoPress do.
  • Match the output to your household. A gravity filter or pump handles batches for several people. A squeeze filter or press bottle suits one person.
  • Plan for clean containers. Treated water needs a clean, covered container. Keep source and treated water containers separate.
  • Check cartridge life and storage. Buy a spare cartridge for any unit you rely on, and follow the maker’s storage directions.
  • Keep it away from chemical hazards. None of these makes fuel- or chemical-contaminated water safe, according to CDC’s guidance.

Which emergency water filter to buy

For most homes, store water first, then add a Sawyer Squeeze as a backup and keep bleach on hand to disinfect what you filter. Choose the Platypus GravityWorks if several people will rely on filtered water, the MSR Guardian if you want virus removal at household volume, and the GRAYL GeoPress for each go-bag. The LifeStraw Peak Squeeze review covers another squeeze filter. For the rest of the kit, see the 72-hour emergency kit guide and the home emergency kit checklist .

Sources checked