What does GPF mean on a toilet?
Three letters on every toilet listing, and one of the few bathroom numbers backed by a federal standard and an independent performance test.
By Sawyer V. · · How we research
The short answer
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Quick picks
Tap any row for the full write-up. Prices are checked against Amazon rather than remembered — where we have no verified figure the button says so.
| # | Product | Best for | Renter | Price |
|---|---|---|---|---|
| 1 |  Adair One-Piece Elongated Toilet, 1.28 gpf 1.28 gpf through an AquaPiston canister, WaterSense certified, at a 12 in. rough-in. | Anyone replacing a toilet today | Owner-only | |
| 2 |  H2Option Two-Piece Dual Flush Chair Height Elongated Toilet with Seat and Wax Ring 0.92 gpf light and 1.28 gpf full, with a published MaP score of 1,000 grams. | Cutting the average flush below 1.28 | Owner-only |
The number itself
GPF is gallons per flush: the volume of water a toilet uses in one full flush, measured at the factory rather than in your house. Its metric twin, Lpf, appears beside it on most listings — 1.28 gpf is 4.8 Lpf.
The two thresholds that matter
The EPA sets both out plainly. There is “the current federal standard of 1.6 gallons per flush”, which is the legal ceiling for new toilets, and there is the WaterSense label, which requires “toilets to use 1.28 gallons per flush or less”.
That is a 20 percent reduction against the federal maximum, and it is why almost every toilet we cover publishes 1.28 gpf: the label has become the market standard.
What lower GPF saves
Toilets are the biggest single indoor water user in a home, “accounting for nearly 30 percent of an average home’s indoor water consumption” on the EPA’s figures. Replacing old ones, it says, means “the average family can reduce water used for toilets by 20 to 60 percent—that’s nearly 13,000 gallons of water savings for your home every year! They could also save more than $170 per year in water costs”.
Does a lower flush clear less?
Not according to the certification. The EPA requires that “All WaterSense labeled tank-type toilets must comply with and are independently certified to meet the same rigorous performance requirements as standard toilets”, including “Mixed testing media flushability”, “Bowl surface cleaning”, “Drainline waste transport” and “Waste extraction”.
There is also an independent score: MaP testing, published in grams of waste cleared. American Standard publishes 1,000 grams for the H2Option; nobody else in our catalog publishes a MaP figure at all, which is worth knowing when a listing talks about flush power without a number.
GPF is not the only number on the flush
- Flush valve size. American Standard publishes 3 in. valves on the Colony 3 and Cadet PRO; a larger valve moves the tank’s water faster.
- Trapway. Published at 2 in. on the Colony 3 and 2-1/8 in. on the Cadet PRO, Santa Rosa, Memoirs Stately and Adair. A fully glazed trapway is published as easier to clear.
- Water surface. Kohler publishes 11 x 8-1/8 in. on the Santa Rosa and 9-5/8 x 7-3/8 in. on the Memoirs Stately. A bigger surface keeps the bowl cleaner; a smaller one is quieter to use.
What GPF does not tell you
It does not tell you how the toilet sounds, how often it needs a second flush in your drain line, or whether the flapper will still seal in five years. Those are the things owners care about and makers do not publish. The honest use of GPF is as a water figure, checked against the WaterSense threshold, and nothing more. The dual-flush toilets are ranked here.
Every pick in full
2 we would buy. Each carries its Renter-Safe Install Rating, the published specs behind it, and the honest gap in what we know.
1. The 1.28 gpf standard
Adair One-Piece Elongated Toilet, 1.28 gpf
Kohler · K-3946 · best for anyone replacing a toilet today
1.28 gpf through an AquaPiston canister, WaterSense certified, at a 12 in. rough-in.
Kohler’s Adair publishes 1.28 gpf (4.8 lpf) with a 2-1/8 in. fully glazed trapway and an 11 x 7-3/4 in. water surface. That is the number nearly every current toilet publishes, because it is what WaterSense requires.
Renter-Safe Install Rating
- Drilling
- None
- Tools
- Not published
- Time to fit
- Not published
- Power
- None
- Reversible on move-out
- No
Why: A full toilet replacement on the property's drainage: out with the old one, new wax ring, new supply connection. An owner's job.
Read from published documentation, not from fitting one. Kohler — Adair K-3946 specification sheet. How the verdict is derived: renter-safe ratings explained.
What’s wrong with it
A one-piece body at 28-9/16 in. deep needs the floor space.
What we can’t tell you
Kohler publishes no MaP score for it.
Published specifications
| Type | One-piece, floor-mount |
|---|---|
| Bowl | Elongated — “offers added room and comfort” |
| Height | Comfort Height; 16-1/2 in. from floor to rim on Kohler's drawing |
| Flush | 1.28 gpf (4.8 lpf), AquaPiston canister |
| Trapway | 2-1/8 in. fully glazed |
| Water surface | 11 in. x 7-3/4 in.; rim to water surface 6-1/16 in. |
| Rough-in | 12 in. |
| Footprint | 28-9/16 in. deep, 16-5/16 in. wide at the tank, 28-7/16 in. tall |
| Seat | Cachet Quiet-Close seat that “quickly unlatches from the toilet for easy removal” |
| Standards | EPA WaterSense; California Energy Commission; ADA when installed to its requirements |
| Warranty | KOHLER Toilets and Seats Limited Warranty — terms are on Kohler's website, not the sheet |
| MaP rating | Not published on the specification sheet |
#ad Price $759.26 as of October 18, 2026. Prices change; Amazon’s listing is the one that counts. How we’re funded.
2. Two numbers on one toilet
H2Option Two-Piece Dual Flush Chair Height Elongated Toilet with Seat and Wax Ring
American Standard · 606AA002.020 · best for cutting the average flush below 1.28
0.92 gpf light and 1.28 gpf full, with a published MaP score of 1,000 grams.
A dual-flush toilet publishes two figures. American Standard’s H2Option publishes “1.28 gpf / 4.8 Lpf full, 0.92 gpf / 3.5 Lpf light” and a MaP rating of “1,000 grams” — the only flush-performance score published among the toilets we cover.
Renter-Safe Install Rating
- Drilling
- None
- Tools
- Not published
- Time to fit
- Not published
- Power
- None
- Reversible on move-out
- No
Why: A full toilet replacement on the property's drainage. The wax ring and seat come in the box, which helps an owner and changes nothing for a tenant.
Read from published documentation, not from fitting one. American Standard — H2Option dual flush chair height elongated toilet, published flush volumes, MaP and contents. How the verdict is derived: renter-safe ratings explained.
What’s wrong with it
White was listed as sold out or unavailable on American Standard's store when we checked.
What we can’t tell you
American Standard does not publish the rough-in on the product page.
Published specifications
| Flush | Dual: 1.28 gpf / 4.8 Lpf full, 0.92 gpf / 3.5 Lpf light |
|---|---|
| MaP rating | “1,000 grams” |
| Water efficiency | WaterSense certified |
| Bowl | Elongated, chair height, “16 1/2-in. high” |
| Actuator | Chrome push-button on the tank lid |
| Included | “Slow-close seat, chrome push-button actuator, color-matched bolt caps, and wax ring” |
| Surface | “EverClean® antimicrobial surface”; “PowerWash® rim” |
| Rough-in | Not published on the product page |
| Warranty | Not published on the product page |
| Availability | White listed as sold out or unavailable on American Standard's store at the time of writing |
#ad Price $419.09 as of October 18, 2026. Prices change; Amazon’s listing is the one that counts. How we’re funded.
Where to buy
Everything recommended on this page, in one place. Each link is an Amazon Associates link — we earn a commission at no extra cost to you, and it never decides a pick.
- $759.26View on Amazon
Adair One-Piece Elongated Toilet, 1.28 gpf
Kohler · K-3946 · Renter verdict: Owner-only
- $419.09View on Amazon
H2Option Two-Piece Dual Flush Chair Height Elongated Toilet with Seat and Wax Ring
American Standard · 606AA002.020 · Renter verdict: Owner-only
#ad Prices are not shown because we only publish figures we have verified on the day. How we’re funded.
Questions people actually ask
what does gpf stand for
Gallons per flush — the volume of water a toilet uses in one full flush. The metric equivalent, Lpf, usually appears beside it: 1.28 gpf is 4.8 Lpf.
what is the federal toilet flush standard
The EPA cites the current federal standard of 1.6 gallons per flush. The WaterSense label goes further and requires 1.28 gallons per flush or less.
do low flow toilets flush as well
The EPA requires WaterSense labeled toilets to be independently certified to the same performance requirements as standard toilets, including waste extraction, bowl surface cleaning and drainline transport.
how much water does a new toilet save
On the EPA's figures, the average family can cut toilet water use by 20 to 60 percent — nearly 13,000 gallons a year — and save more than $170 a year in water costs.
Sources
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