Water Filter Replacement: How Often, per NSF and CDC Guidance

What It Means

Water filter replacement means changing the cartridge in a pitcher, faucet, under-sink, fridge or whole-house filter before it wears out. NSF, which certifies filters, says a filter certified to its standard 53 must have a stated capacity, meaning how much water it can treat before it needs changing, and that figure is in the manual or on the box. CDC adds a health reason: germs can live and multiply in a filter that isn't maintained and replaced on the maker's schedule.

Try It: When Will This Filter Run Out?

Enter your filter's rated capacity from its manual or box, and roughly how much water goes through it a day. The starting numbers are only examples.

Rated capacity (gallons)Gallons filtered a day

Days until it's used up40

About how many weeks5

If the maker also gives a time limit, change it at whichever comes first.

How It Sounds at Home

"When did we last change the pitcher filter?"
"The light on the filter's gone red."
"Grab a replacement cartridge, the water tastes off."

The Breakdown

How often, per NSF, CDC and the makers

Filter	When to replace it	Source
Any NSF/ANSI 53 certified filter	When it reaches its rated capacity in gallons	NSF
Any home water filter	On the maker's schedule, before it expires	CDC
Whole-house filter	On the maker's schedule; some remove the chlorine that keeps germs down	CDC
Refrigerator filter	Usually about every six months	Whirlpool

Which standard is which, per NSF

Standard	What a certified filter reduces
NSF/ANSI 42	Taste and odor issues such as chlorine
NSF/ANSI 53	Contaminants with a health effect
NSF/ANSI 401	Up to 15 emerging contaminants found at trace levels

Make it last between changes. Write the install date on the housing or in your calendar. Buy the replacement the maker specifies or one certified for your housing, since NSF warns that a look-alike cartridge can leave a gap that lets water flow around it.

Good to Know

CDC says germs that grow in the slime inside pipes can live and multiply in a water filter that isn't maintained and replaced, and some whole-home filters take out the chlorine that would otherwise kill them. Follow your own filter's manual for the interval and any flushing it asks for after a change. A filter only reduces what it's certified for, so check the standard on the box against what you want it to do, and ask your water supplier or local health department if you have a specific worry about your water.

FAQ

How often should I replace my water filter?

When it reaches the capacity or time the maker lists, whichever comes first. NSF says the capacity is in the manual or on the packaging, and CDC says to replace filters on the maker's schedule.

What happens if I don't change my water filter?

It can stop reducing what it's certified for, and CDC warns germs can grow inside a filter that isn't maintained and replaced.

Are cheaper look-alike cartridges OK?

NSF cautions that a non-certified cartridge may not seal in the housing, letting water go around it, and may be made of materials never checked for drinking water. Use the maker's part or one certified for your system.

Do It in Buhata

Maintenance and Vault

Add "Replace the water filter" to Maintenance in the Household X add-on at your filter's interval, and keep the cartridge model in Vault (Plus).

Open Buhata

Related Terms and Categories

Fridge water filter
The replaceable cartridge that filters water for a refrigerator's dispenser and ice maker, usually changed about every six months.
Water softener
A home system that removes the calcium and magnesium that make water hard, usually by trading them for sodium in a tank of resin beads.
Hard water stains
White, chalky marks left on glass, faucets, tile and toilets when hard water dries and leaves its calcium and magnesium behind.
HVAC filter
The removable filter in a furnace, central air conditioner or heat pump that traps dust from the air; ENERGY STAR says check it monthly and change it at least every 3 months.
Fridge deep clean
A full clean of the refrigerator with the food and shelves out, the parts washed, and the inside cleaned and sanitized, beyond wiping up spills.

Home maintenance and repairs

Sources

NSF, "Changing Water Filters"; NSF, "NSF/ANSI 42, 53 and 401: Filtration Systems Standards"; NSF, "Water Filters FAQs"; CDC, "Preventing Waterborne Germs at Home"; CDC, "About Choosing Home Water Filters"; Whirlpool, "How Often Should You Change Your Refrigerator Water Filter?"

Last updated September 30, 2026.