How to tell if a generic filter is certified

"Meets NSF standards" or "tested to NSF protocols" is not the same as being certified. Only a product in the NSF listing (or another accredited certifier's listing, such as IAPMO or WQA) is actually certified.

What the standards mean

• NSF/ANSI 42 (aesthetic): taste, odor, chlorine, particles. It does not cover health contaminants like lead.
• NSF/ANSI 53 (health): health-related contaminants such as lead, cysts and some VOCs. Each product is certified for specific contaminants, so check the list.
• NSF/ANSI 401 (emerging contaminants): trace pharmaceuticals and chemicals. Whirlpool's data sheet calls these "emerging compounds/incidental contaminants".

Many cheap generics are certified to 42 only, meaning chlorine and taste. If lead matters to you, look for 53 with lead reduction listed.

How to check the NSF listings

1. Go to the NSF drinking water treatment units listings.
2. Search by trade name (the brand, like "Waterdrop") or company name.
3. Find the exact model number on the box. Brands often sell a cheap 42-only version and a pricier 42/53/401 version with nearly the same name (for example, Waterdrop WD-, WDS- and WDP- versions).
4. Check which standard section the model appears under and which contaminants are listed.
5. No listing? Treat the claim as unverified.

Note: the NSF listing confirms certification, not fit. Fit comes from the seller.