Skip to content
TapBuff
ZIP

iSpring US31 3-Stage Under Sink Water Filtration System

Checked against its certification listings: what they cover, what the maker claims, and what it costs over five years.
Under-sink carbon

Listings checked Oct. 16, 2026

Certified to

Not on any listing

NSF, WQA, IAPMO, checked Oct. 16, 2026. Every claim on this page is the maker’s alone.

Maker’s list price

$143

as of Oct. 16, 2026

Each replacement, at list price

Replacement filter set (F3)
$32

Five years, household of 3

$431

7.9¢ per gallon

Disclosure: TapBuff earns a commission if you buy through some links on this page. It does not change which standard or filter we name. As an Amazon Associate, TapBuff earns from qualifying purchases. How TapBuff makes money

Price on AmazonThe maker’s page

List price from the maker’s site, checked Oct. 16, 2026. Prices change; the maker’s page is the final word.

No certification found

Not on any listingNSF, WQA, IAPMO, checked Oct. 16, 2026

TapBuff searched the certifiers’ own listings and found nothing for this product. That does not mean it does not work. It means no independent certifier has confirmed what it reduces, so every claim below is the maker’s alone.

Certified for, and claimed

Certified, by a listing

Nothing.

Claimed by the maker only

  • sediment
  • chlorine taste and odor
  • chloramine
  • heavy metals
  • PFAS

Certification claims we could not find on a listing

  • iSpring's product name says "NSF Certified", and its description says the system was "tested by independent third party against NSF/ANSI standards (42, 53, 61)." No listing for the US31 was found at NSF, WQA or IAPMO on Oct. 16, 2026. NSF lists iSpring only for reverse osmosis systems, under NSF/ANSI 58.

What it costs over five years

Household of 3, 3 gallons a day of drinking and cooking water. Installation not included.

ItemReplacedCountAmount
System, with first media—1$143
Replacement filter set (F3)Every 6 monthsmonth rating9$288

Five-year total$431

Per gallon7.9¢

Run it for your household

Worth knowing

No certification found. iSpring publishes no gallon ratings. It says to replace the filters every 6 to 12 months, and lists the sediment filter (FP15) at up to 6 months and the two carbon filters (FG15, FC15) at up to 12; the F3 set holds all three, so the 6-month figure is recorded. Prices are the $142.99 and $31.99 regular prices.

Other under-sink carbon filters

All filters

Where to go next