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Emergency prep

Certified beats claimed. Water filters ranked on proof.

Most emergency filters are not purifiers, and most purifier claims are the maker's own. When we checked NSF's public purifier listing, it held just two makers. Here is what each product can show.
What do I need?See the list

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Filter or purifier? Check your water source

Pick where your water will come from. We show what treatment it needs and which standard to look for.

Where will your water come from?

You need

A purifier, or boil or bleach after filtering

Water of unknown quality can carry viruses as well as bacteria and parasites. CDC says filters alone do not remove viruses, so use a purifier, or filter and then disinfect.

Look for certification to

  • NSF P231: Microbiological purifiers for water of unknown quality: bacteria, viruses and cysts. Based on the EPA 1987 Guide Standard.
  • NSF P248: A US Army and NSF protocol for emergency and field purifiers, with tougher test water.

How we rank

We rank on evidence, not features or reviews. Strongest first:

  1. In a certifier's public listing. You can find the model under that standard yourself.
  2. Maker names a third-party certifier. The maker says a certifier such as IAPMO certified it.
  3. Maker's own claim only. The maker says it "meets" or was "tested to" a standard.

A product is on this page only if we could read its standards claim on the maker's page or a certifier's listing. We checked every claim on October 26, 2026. We list no prices.

Purifiers: for water of unknown quality

Only one of these isin a certifier's listing. The rest are worth considering, but read the claim for what it is.

1. Multipure Aquapremier (CBXT element)

In a certifier's public listing

Home unit plumbed in to its own tap

Listed by NSF under Standard P231 (Microbiological Water Purifiers) for bacteria, live cyst and virus reduction.

  • Works from your tap, so it needs water pressure. It is no help if the taps run dry.
  • One of only four products, from two makers, in NSF's P231 listing when we checked.

Claim read on NSF's listing on October 26, 2026 · See it at Multipure (opens in a new tab)

2. MSR Guardian Gravity Purifier

Maker's own claim only

Gravity purifier for a household, 10-liter bag

Maker says it meets NSF Protocol P248 for removing viruses (99.99%), and the US EPA Guide Standard and Protocol for Testing Microbiological Purifiers.

  • Maker's spec sheet lists it as not effective against chemicals or toxins.
  • Not in NSF's public P231 listing; the P248 claim is the maker's.

Claim read on the maker's page on October 26, 2026 · check the listing · See it at MSR (Cascade Designs) (opens in a new tab)

3. LifeStraw Peak Series Gravity Purifier

Maker's own claim only

Gravity purifier, 8-liter bag

Maker says it meets US EPA and NSF P231 drinking water standards for removing viruses, bacteria and parasites.

  • Not in NSF's public P231 listing when we checked; the maker says it was independently lab-tested.

Claim read on the maker's page on October 26, 2026 · check the listing · See it at LifeStraw (opens in a new tab)

4. LifeStraw Family

Maker's own claim only

Gravity purifier sized for a family

Maker says it meets NSF/ANSI P231 for reducing viruses, bacteria and parasites, and was lab-tested to WHO, US EPA and WQA standards.

  • Maker says it does not remove fluoride or chlorine.
  • Not in NSF's public P231 listing when we checked.

Claim read on the maker's page on October 26, 2026 · check the listing · See it at LifeStraw (opens in a new tab)

5. Grayl GeoPress Purifier (24 oz)

Maker's own claim only

Press bottle for one person, about 24 oz at a time

Maker says it meets or exceeds the US EPA Water Purifier standard for microbiological filtration, and was tested by a certified lab to NSF/ANSI protocols 42 and 53.

  • One bottle at a time: good for one person, slow for a household.
  • Not in NSF's public listings when we checked; the claims are the maker's.

Claim read on the maker's page on October 26, 2026 · check the listing · See it at Grayl (opens in a new tab)

Tap water filters: for water that is already treated

These improve tap water you already trust. They are not purifiers, and neither works as a substitute for boiling during a boil-water notice.

1. AquaTru Classic countertop reverse osmosis

Maker names a third-party certifier

Countertop filter for tap water; plugs into the wall

Maker says it is independently tested and certified by IAPMO to NSF standards to reduce 84 contaminants found in tap water.

  • For tap water, not water of unknown quality: it is not a P231 purifier.
  • Needs a 120-volt outlet, so it stops in a power outage unless you have backup power.
  • Check the exact model in IAPMO's listing database.

Claim read on the maker's page on October 26, 2026 · check the listing · See it at AquaTru (opens in a new tab)

2. Epic Pure XP dispenser

Maker's own claim only

Pour-through dispenser for tap water

Maker says it is NSF certified to NSF/ANSI 42 and 372, and independently tested to NSF/ANSI 42, 53, 401 and P231. NSF's listing shows the PureXP cartridge certified for material safety only.

  • NSF's public listing for the PureXP cartridge says: certified for material safety requirements only.
  • The maker's page names P231 in one place and P473 in another; we could not confirm either.
  • Sold for municipal or well water, not water of unknown quality.

Claim read on the maker's page on October 26, 2026 · check the listing · See it at Epic Water Filters (opens in a new tab)

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Standards, in plain English

Water filter standards and what each covers
StandardWhat it covers
NSF/ANSI 42Taste and odor only, such as chlorine and particles. Not a health claim.
NSF/ANSI 53Health contaminants in tap water, such as lead, some chemicals and cysts. Only the contaminants listed for that model.
NSF/ANSI 58Reverse osmosis systems: dissolved solids and listed contaminants such as arsenic and nitrate.
NSF/ANSI 401Some emerging contaminants, such as certain drugs and microplastics.
NSF P231Microbiological purifiers for water of unknown quality: bacteria, viruses and cysts. Based on the EPA 1987 Guide Standard.
NSF P248A US Army and NSF protocol for emergency and field purifiers, with tougher test water.

CDC adds: to remove parasites such as Cryptosporidium, look for NSF 53 or 58 with "cyst reduction" or an absolute pore size of 1 micron or smaller.

How to look a product up yourself

  1. Open NSF's certified water treatment listings (opens in a new tab).
  2. Type the maker's name, or pick a standard such as Microbiological Water Purifiers (NSF P231).
  3. Find the exact model. Read the claims listed beside it: a listing can cover materials only, or one contaminant only.
  4. Not there? Try IAPMO's listings (opens in a new tab) or WQA's product search (opens in a new tab). If it is in none of them, the claim is the maker's own.
When we searched the P231 purifier listing on October 26, 2026, it held four products from two makers (opens in a new tab), all home units on a tap. None of the portable or gravity brands sold for emergencies were in it.

Left off this list

  • Berkey. Named in a 2023 EPA stop-sale order. See the FAQ below.
  • Alexapure. Publishes no certifications we could find.
  • Squeeze and straw filters whose pages name no standard. The Sawyer Squeeze page, for example, cites its own lab report for bacteria and protozoa and says nothing about viruses or any standard. That is a filter, not a purifier.

For tank filters in vans and RVs, see Camper Volts.

Frequently asked questions

What is the difference between a water filter and a water purifier?

A purifier is tested to remove viruses as well as bacteria and parasites, so it can treat water of unknown quality. The line comes from the EPA's 1987 Guide Standard: 6-log (99.9999%) of bacteria, 4-log (99.99%) of viruses and 3-log (99.9%) of cysts. CDC says most portable filters remove parasites but not viruses or bacteria.

What NSF certification should an emergency water filter have?

For water of unknown quality, such as a creek, rain barrel or tap water under a boil notice, look for a microbiological purifier claim: NSF P231 or P248, both built on the EPA Guide Standard. For safe tap water with a specific problem such as lead, look for NSF/ANSI 53 or 58 for that contaminant. NSF/ANSI 42 covers taste and odor only.

How do I check if a filter is really NSF certified?

Search the maker's name in NSF's public listings at info.nsf.org/Certified/DWTU, pick the standard, and look for the exact model and the claims listed for it. Some products are certified by IAPMO or WQA instead; both have their own search. "Tested to" or "meets" a standard is the maker's claim. "Certified to" should come with a listing you can find.

What about Berkey?

We do not list Berkey. On May 8, 2023 the EPA ordered Berkey International LLC to stop selling Black Berkey filters and the Berkey systems sold with them, including the Big, Travel, Royal, Imperial and Crown (order FIFRA-08-2023-0038). The EPA said the labels and websites claimed the filters removed viruses and bacteria, and that silver self-sterilized them, which makes them pesticides under federal law, and that none were registered with the EPA. That is a registration and labeling ruling, not a test of the water. Berkey sued the EPA in federal court in Puerto Rico in March 2024 to challenge the order. We have not confirmed where that case stands now.

Do I need a filter if I store water?

Stored water comes first. A purifier is the backup for when stored water runs out. For a household, a gravity purifier such as the MSR Guardian Gravity Purifier or the LifeStraw Family treats water in batches without pumping.

We are not a testing lab. Every claim here is quoted from the source linked beside it, on the date shown. Makers change products and pages; check the listing before you buy. Not medical advice. See our disclaimer.

Sources

  1. NSF, Certified Drinking Water Treatment Units listings — search by maker or standard
  2. NSF listing: Standard P231 Microbiological Water Purifiers — 2 makers, 4 products when checked October 26, 2026
  3. CDC, Making Water Safe in an Emergency — most filters remove parasites but not viruses or bacteria; pore sizes
  4. CDC, A Guide to Water Filters (Cryptosporidium) — NSF 53 or 58 cyst reduction; absolute 1 micron
  5. US EPA Region 8, Stop Sale, Use or Removal Order to Berkey International LLC, FIFRA-08-2023-0038 (PDF) — May 8, 2023: Black Berkey filters and systems; virus and bacteria claims; not registered
  6. Berkey International LLC v. EPA, complaint, US District Court for Puerto Rico, filed March 6, 2024 (PDF, hosted by EPA)
  7. Multipure Aquapremier (CBXT element): NSF listing — checked October 26, 2026
  8. MSR Guardian Gravity Purifier: maker's page — checked October 26, 2026
  9. LifeStraw Peak Series Gravity Purifier: maker's page — checked October 26, 2026
  10. LifeStraw Family: maker's page — checked October 26, 2026
  11. Grayl GeoPress Purifier (24 oz): maker's page — checked October 26, 2026
  12. AquaTru Classic countertop reverse osmosis: maker's page — checked October 26, 2026
  13. Epic Pure XP dispenser: maker's page — checked October 26, 2026
  14. Sawyer Squeeze product page — checked October 26, 2026

Keep going

Photo: Devon MacKay on Unsplash (Unsplash License).