Store safe water first: Reliance Aqua-Tainer jugs year-round, a waterBOB the night before a storm. Then a filter: Sawyer Squeeze for go-bags, Platypus GravityWorks for a family, GRAYL GeoPress if you want virus protection. Filters handle specific contaminants; none makes fuel- or chemical-contaminated water safe. Follow local water advisories.
Enough volume for a family's drinking water at camp or in an outage
OutdoorGearLab's top group filter
Keep in mind
No virus protection
Needs somewhere to hang it, about shoulder height
Slows down in silty water until you backflush
Platypus GravityWorks 4.0L Water Filter System specifications
Type
Gravity filter with separate 4L dirty and 4L clean reservoirs
Removes
Bacteria, protozoa and particulates; not viruses or chemicals (Platypus)
Filter rating
0.2 micron hollow fiber
Flow
1.75 L/min (Platypus)
Cartridge life
1,500 liters (Platypus)
Weight
11.5 oz (326 g)
Maintenance
Backflush in the field by reversing flow
Capacity
4L dirty + 4L clean reservoirs
Image: GRAYL
05Best for viruses
The cautious pick.
GRAYL GeoPress 24 oz Purifier · 5 of 5
YesRemoves viruses (GRAYL)
8 secPer 24 oz (GRAYL)
65 galCartridge life (GRAYL)
24 ozPer press
Get it if You want one bottle rated for viruses, with carbon that GRAYL says adsorbs many chemicals and heavy metals, for travel or sketchy taps.
Skip it if You suspect fuel, industrial or toxic contamination; GRAYL says to find another source. Or you need water for a family. About 65 gallons per cartridge.
Strengths
The only pick here that GRAYL rates for viruses as well as bacteria and protozoa
OutdoorGearLab got clear water from a metal-polluted river with it
No setup: fill, press, drink
Keep in mind
Short, costly cartridge life: about 65 gallons
One person's water at a time
Not for industrial spills, high lead, mercury or toxic algae (GRAYL)
The only pick here that GRAYL rates for viruses as well as bacteria and protozoa
OutdoorGearLab got clear water from a metal-polluted river with it
No setup: fill, press, drink
Keep in mind
Short, costly cartridge life: about 65 gallons
One person's water at a time
Not for industrial spills, high lead, mercury or toxic algae (GRAYL)
GRAYL GeoPress 24 oz Purifier specifications
Type
Press-action purifier bottle
Removes
Viruses, bacteria and protozoan cysts; carbon adsorbs many chemicals and heavy metals, but not built for industrial spills, high lead, mercury or toxic algae (GRAYL)
Speed
8 seconds per 24 fl oz (GRAYL)
Cartridge life
About 350 presses / 250L / 65 gal (GRAYL)
Capacity
24 fl oz per press
Colors
Several; same purifier
Side by side.
Pick two. Compare the numbers—not the marketing.
Manufacturer specs. Virus claims matter most: only the GRAYL is rated for viruses here.
Squeeze filter; also inline or gravity with the included tubing
Gravity filter with separate 4L dirty and 4L clean reservoirs
Press-action purifier bottle
Removes
Nothing: storage only
Nothing: storage only
Bacteria and protozoa (Giardia, Cryptosporidium) per Sawyer; not viruses or chemicals
Bacteria, protozoa and particulates; not viruses or chemicals (Platypus)
Viruses, bacteria and protozoan cysts; carbon adsorbs many chemicals and heavy metals, but not built for industrial spills, high lead, mercury or toxic algae (GRAYL)
Capacity
7 gallons (26 L)
Up to 100 gallons, depending on your tub (waterBOB)
Viruses, bacteria and protozoan cysts; carbon adsorbs many chemicals and heavy metals, but not built for industrial spills, high lead, mercury or toxic algae (GRAYL)
Capacity
24 fl oz per press
How we chose
Capacities, ratings and what each filter removes come from the manufacturers. Field verdicts come from OutdoorGearLab, which compared 26 filters and purifiers. How much to store comes from Ready.gov; how to treat water comes from the CDC and EPA. We don’t run our own lab tests, and we haven’t joined any of these brands’ affiliate programs.
Store first, filter second
One gallon per person per day. That’s the Ready.gov minimum, for drinking and sanitation, for several days. Kids, nursing mothers, sick people and hot weather need more. A family of four needs 12 gallons for three days.
Rotate it. Water you bottle yourself should be replaced every six months. Use food-grade containers, clean them with dish soap, and keep them cool and dark (Ready.gov).
Filters are the backup. They treat specific germs in creek or rain water. None is a blanket fix for floodwater or chemical spills, and none helps if you have nothing to filter.
Don’t drink pool or spa water. The CDC says it’s for hygiene and cleaning only. If you suspect fuel or toxic chemicals in any water, boiling, bleach and filters won’t fix it. Use another source and call your health department.
Filter vs purifier, in plain English
Hollow-fiber filters like the Sawyer and the Platypus stop bacteria and protozoa such as Giardia and Cryptosporidium. They don’t stop viruses or chemicals, as OutdoorGearLab and the makers both say. The CDC says portable filters don’t remove viruses and suggests adding a chemical disinfectant after filtering. A purifier like the GRAYL GeoPress is rated for viruses too, but GRAYL says it isn’t built for industrial spills, high lead, mercury or toxic algae.
Boiling kills germs best. The CDC says: let cloudy water settle or strain it through a cloth, then bring clear water to a rolling boil for 1 minute. Above 6,500 feet, boil for 3 minutes. Boiling does not make chemically contaminated water safe.
Bleach is the fallback. Use plain, unscented chlorine bleach meant for disinfection; no scented, color-safe or added-cleaner bleach (EPA). Follow the label first. If it has no water directions, the CDC’s table for 5–9% bleach is 8 drops per gallon, doubled for cloudy, colored or very cold water. Stir and wait at least 30 minutes. Bleach doesn’t work as well as boiling on Giardia and Cryptosporidium.
Also worth a look
MSR Guardian. OutdoorGearLab’s pick for murky water: a pump purifier rated for viruses that cleans itself as you pump. It’s heavy and costs several times more than the Sawyer. We’ll add it once we’ve checked listings.
