1.28 GPF vs 1.6 GPF Toilets: Which to Choose

GPF stands for gallons per flush, and it is the single number that defines how much water a toilet uses every time you push the handle. For decades, 1.6 GPF was the federal standard in the United States, set by the Energy Policy Act of 1992 and effective in 1994. More recently, 1.28 GPF has become the modern efficiency benchmark, driven by the EPA WaterSense program and adopted as the mandatory maximum in water-conscious states like California, Texas, Colorado and Georgia. The two numbers look close on paper, a difference of only 0.32 gallons per flush, but that small gap adds up fast across thousands of flushes a year, and it sits at the center of a real buying decision.

The old assumption was simple: less water meant a weaker flush. That was true in the 1990s, when the first low-flow toilets clogged constantly and earned a bad reputation that still lingers. It is no longer true. Today's best 1.28 GPF toilets use redesigned trapways, larger flush valves and engineered bowl geometry to clear the same waste load as a 1.6 GPF toilet, and the published MaP (Maximum Performance) flush-test scores prove it. Many 1.28 GPF models post the same 1,000 gram MaP ceiling as their 1.6 GPF predecessors. This guide compares the two standards on the data that actually matters, then names the specific models worth buying. For the broadest cross-standard ranking of flush power, the pillar guide to the best flushing toilets places both alongside every major brand.

The table makes the central point clearly: on flush power, the two standards are tied at the top. A well-engineered 1.28 GPF toilet clears the same MaP gram load as a 1.6 GPF toilet, so you are not trading flush performance for water savings the way buyers had to in the past. Where 1.28 GPF wins decisively is water use, WaterSense certification, legal eligibility in efficiency-mandated states and utility rebates. The only genuine advantage left for 1.6 GPF is a sliver of extra drain-line carry water, which matters in a narrow set of older homes with long, low-slope waste lines. For everyone else, the modern 1.28 GPF standard is the smarter buy.

You want real, measurable water savings

The math is straightforward and it favors 1.28 GPF every time. A 1.6 GPF toilet uses 0.32 gallons more per flush. The EPA estimates a typical person flushes about five times a day, so across a four-person household that is roughly 20 flushes daily, or about 6.4 gallons saved per day with 1.28 GPF. Over a year that is more than 2,300 gallons for that household, and the EPA puts the lifetime savings of switching from older fixtures into the tens of thousands of gallons. On a metered water and sewer bill, that is a recurring saving you feel every month, not a one-time perk. For a deeper look at the lowest-water options, the roundup of the best water saving toilets of 2026 ranks the most efficient models that still flush hard.

You want EPA WaterSense certification and rebates

WaterSense is the EPA's voluntary certification, and a toilet earns it only by using 1.28 GPF or less while passing independent flush-performance testing. A 1.6 GPF toilet, by definition, cannot carry the WaterSense label because it exceeds the water threshold. That label is not just a badge: many municipal water utilities offer rebates of meaningful value for installing a WaterSense toilet, and some states require it for new installs. If a rebate is available in your area, it can offset a large share of the toilet's cost. The roundup of the best EPA WaterSense certified toilets lists models that qualify and flush at the top of the MaP charts.

You are building, remodeling or live in a regulated state

This one is not optional in much of the country. California, Texas, Colorado, Georgia and several other states have made 1.28 GPF the mandatory maximum for new toilet installations. If you are in one of those states, a 1.6 GPF toilet is simply not a legal new-install choice, and big-box retailers in those markets no longer stock them for residential sale. Even where 1.6 GPF remains legal, building a new home or doing a full remodel is the moment to standardize on the efficient fixture, since you gain the water savings for the entire life of the home with zero performance penalty from a good model.

You have a long, low-slope or troubled waste line

The one real engineering argument for 1.6 GPF is drain-line carry. A flush has to move solid waste not just out of the bowl but all the way down the building drain to the sewer or septic line. In an older home with a long horizontal run, a low slope (below the ideal quarter-inch-per-foot pitch), or a history of slow drains, the extra 0.32 gallons of carry water can provide a margin that prevents waste from stalling partway down the pipe. This is a real but narrow scenario. If your home has never had drain-carry problems on a 1.28 GPF or even an older fixture, it is not your situation, and a strong-flushing 1.28 GPF toilet will carry waste just fine.

You are replacing one fixture in an unregulated state and reuse parts

If you live where 1.6 GPF remains legal and you are matching an existing pair of toilets, some buyers prefer to keep the standard consistent for predictable behavior and shared spare parts. This is a convenience argument, not a performance one, and it grows weaker every year as 1.28 GPF becomes the default everywhere. We would still steer most of these buyers to a high-MaP 1.28 GPF model, because the water savings compound for years while the flush performance is identical.

You specifically need a pressure-assisted heavy-duty fixture

Some pressure-assisted toilets, which use building water pressure to force a powerful flush, are built at 1.6 GPF for the most demanding commercial-adjacent residential use. If you genuinely need that level of flush force, for example a high-traffic bathroom that punishes gravity toilets, a 1.6 GPF pressure-assist model is a defensible choice. That said, 1.28 GPF pressure-assisted models now exist and perform extremely well, so the water standard is rarely the deciding factor even here.

1

Best 1.28 GPF overall

TOTO Drake (CST744E, 1.28 GPF)

4.7 Efficient powerhouse

The 1.28 GPF Drake is the toilet that retired the low-flow stigma, clearing a 1,000 gram MaP load on less water than the old federal standard required.

Flush TypeGravity, G-Max siphon

GPF1.28

MaP Score1,000 g

Bowl HeightUniversal (chair)

Warranty1-year limited

Best For

• Buyers who want top flush power and WaterSense efficiency
• Busy family bathrooms that demand clog resistance
• Anyone in a state that mandates 1.28 GPF

Not Ideal For

• Shoppers on the tightest budget
• Homes needing a one-piece or skirted look

The Drake's G-Max flushing system pairs a wide 3-inch flush valve with a fully glazed, computer-designed trapway, so a small volume of water leaves the tank fast and creates a strong siphon. That is the engineering reason a 1.28 GPF toilet can match a 1.6 GPF flush on MaP testing.

Owner reviews are overwhelmingly positive on flush strength and clog resistance, with the brand's reputation for reliability a recurring theme. The most common note is that the two-piece styling is plain and the standard seat is sold separately on some configurations.

Expert Take

If someone asks for one toilet that settles the 1.28 vs 1.6 question, this is it. It proves you can have the lower water bill and the strong flush at the same time, which is exactly why we make it the default recommendation across the site.

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Bottom Line: The Drake is the clearest proof that a 1.28 GPF toilet gives up nothing in flush power.

2

Best 1.6 GPF heavy duty

American Standard Champion 4 (1.6 GPF)

4.5 Problem drain lines

The Champion 4 is the model to buy when you genuinely need 1.6 GPF, pairing the most carry water with a huge valve for older, troubled waste lines.

Flush TypeGravity, 4-inch valve

GPF1.6

MaP Score1,000 g

Bowl HeightRight Height (chair)

Warranty10-year limited

Best For

• Older homes with long, low-slope drain lines
• High-traffic bathrooms that punish weaker flushes
• Anyone who has fought repeated clogs and wants margin

Not Ideal For

• Water-conscious buyers chasing the lowest bill
• New installs in states that cap GPF at 1.28

The Champion 4 uses an oversized 4-inch flush valve and a wide 2-3/8-inch fully glazed trapway, which together push a large slug of water with serious force. With 1.6 gallons behind it, the drain-line carry margin is about as high as a residential gravity toilet gets.

Owner reviews praise its near-unclogggable reputation and ease of use, with the main reminders being that 1.6 GPF cannot earn WaterSense and is not a legal new install in efficiency-mandated states. Where it is allowed, it is a workhorse.

Expert Take

We only recommend a 1.6 GPF toilet for a specific reason, and a documented drain-carry problem is that reason. The Champion 4 is the model we point those buyers to, because if extra water is going to solve the issue, this is the fixture that delivers it with the most force.

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Bottom Line: The best reason to buy 1.6 GPF, and the Champion 4 is the model that earns it.

3

Best dual-flush compromise

TOTO Aquia IV (0.8 / 1.28 GPF)

4.6 Maximum water savings

The Aquia IV uses two buttons to default to a 0.8 GPF flush for liquids and a 1.28 GPF flush for solids, beating both fixed standards on average water use.

Flush TypeDual-flush, Tornado

GPF0.8 / 1.28

MaP Score800 g (full flush)

Bowl HeightUniversal (chair)

Warranty1-year limited

Best For

• Households chasing the lowest possible water bill
• Buyers who want a full flush in reserve for heavy loads
• Modern bathrooms wanting a skirted, easy-clean design

Not Ideal For

• Anyone who dislikes choosing between two buttons
• Tight budgets, since dual-flush costs more

The Aquia IV's Dynamax Tornado wash uses two angled nozzles instead of rim holes to swirl water around the bowl, which keeps the bowl clean on the lower water volumes a dual-flush demands. The CeFiONtect glaze resists waste sticking, further reducing the water needed to keep it spotless.

Owner reviews highlight the genuine water savings and the clean, skirted styling, with the main caution being that the reduced flush is for liquids only, so households need to use the full button for solids to avoid streaking.

Expert Take

For the buyer who wants the absolute lowest water use without the clog anxiety of a single low-flow flush, dual-flush is the smartest answer. The Aquia IV gives you sub-1-gallon flushes most of the day and a full 1.28 GPF flush whenever you need it, which sidesteps the whole 1.28 vs 1.6 dilemma.

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Bottom Line: A dual-flush toilet beats both fixed standards on real-world average water use.

Does a 1.28 GPF toilet flush as well as a 1.6 GPF toilet?

How much water does a 1.28 GPF toilet save versus 1.6 GPF?

Is 1.6 GPF still legal to install?

What is a good MaP score for a 1.28 GPF toilet?

Below the 1.28 GPF standard sits an even more efficient tier. A growing number of toilets now flush at 1.0 GPF or even 0.8 GPF while still passing MaP testing, which is the frontier of water efficiency. If saving the most water possible is your goal, the roundup of the best low flow toilets (1.28 GPF and under) ranks the models that push below the WaterSense threshold without clogging. For buyers focused on overall environmental impact, including manufacturing and longevity, the guide to the best eco friendly toilets for a greener bathroom takes a wider view. Across all of these, the same brands lead: TOTO sets the flush-engineering benchmark, Kohler leads on design and finish with models like the Highline and Cimarron, American Standard and Gerber deliver strong flushing per dollar with the Cadet 3 and Avalanche, and Woodbridge and Swiss Madison bring modern styling at value prices. The water standard you choose matters less than picking a model from a reliable brand with a high MaP score.

The water-efficiency argument that once required a real trade-off no longer does. Modern 1.28 GPF toilets match the flush power of 1.6 GPF models on the data that matters, the MaP flush test, while using nearly 20 percent less water on every flush. That means lower water and sewer bills, eligibility for utility rebates, the EPA WaterSense label and compliance with the laws in a growing list of states, all for no loss in performance from a well-chosen model. The only buyers who should still consider 1.6 GPF are those with a documented drain-line carry problem on a long, low-slope waste line, and even many of them are well served by a high-MaP 1.28 GPF toilet or a dual-flush model. For everyone else, choose 1.28 GPF, buy a model with a MaP score of 800 grams or higher, and check the current price on Amazon for the exact model you pick.