Toilet Water Use Comparison: GPF Chart All Popular Models

What Does GPF Mean and Why Does It Matter?

Every toilet sold in the United States since 1994 must meet the federal maximum of 1.6 gallons per flush, a mandate from the Energy Policy Act of 1992. Before that cutoff, standard models used 3.5 GPF and older pre-1980 toilets often used 5 to 7 GPF. The shift to 1.6 GPF saved billions of gallons of water nationwide but also created the first wave of consumer complaints about chronic clogs -- early low-flow models cut water volume without redesigning the trapway or flush valve, so waste did not clear reliably.

Engineering caught up over the following decade. Wider trapways (2 inches and larger), larger flush valves (3-inch vs. the older 2-inch), and pressurized or power-assisted flush systems restored clog resistance at 1.6 GPF. Then the EPA WaterSense program, launched in 2006, pushed manufacturers to certify toilets at 1.28 GPF -- a 20 percent reduction from the 1.6 GPF standard -- while requiring those models to pass MaP (Maximum Performance) flush testing at a minimum of 350 grams of solid waste. Most WaterSense-certified toilets today clear 600 to 1,000 grams, far beyond that floor.

Understanding GPF in isolation is not enough. The MaP score, trapway diameter, and bowl shape all determine whether a toilet truly performs at its rated water volume. This guide maps GPF ratings across all major toilet lines, pairs each rating with available MaP data, and explains which tier makes sense for different households and plumbing setups.

What Are the Different GPF Tiers Available Today?

0.8 GPF -- Ultra-High-Efficiency

The lowest single-flush volume widely available comes from the dual-flush side of toilets like the TOTO Aquia IV Dual Flush, which offers a 0.8 GPF light-flush mode for liquid waste alongside a 1.28 GPF full flush. Some commercial-grade fixtures reach 0.5 GPF using pressurized systems, but those are not practical for residential retrofits. At 0.8 GPF, a toilet requires an exceptionally wide trapway and a powerful siphon action or pressure assist to clear solid waste reliably. MaP scores at this volume tend to cluster around 500 to 700 g -- adequate for most adults but tighter than the headroom offered at 1.28 GPF.

1.0 GPF -- High-Efficiency

A small number of models, mostly from TOTO and Kohler's commercial lines, operate at 1.0 GPF. TOTO's Ultramax II is available in a 1.0 GPF configuration in some markets. At this volume, brands rely on double-cyclone or Tornado Flush technology that uses directed water jets rather than a wide rim wash to create enough siphon force. MaP scores at 1.0 GPF for leading models reach 800 to 1,000 g, which is genuinely impressive and comparable to many 1.6 GPF toilets from five years ago.

1.28 GPF -- WaterSense Standard

This is the dominant tier in 2026. Any toilet at 1.28 GPF bearing the EPA WaterSense label has been independently tested to pass the MaP protocol at a minimum of 350 g -- but brand leaders typically land at 800 to 1,000 g. The 1.28 GPF tier qualifies for rebates from hundreds of water utilities across the country and in Canada. Models include the TOTO Drake II, TOTO UltraMax II, Kohler Cimarron, Kohler Highline Arc, American Standard Cadet 3, Woodbridge T-0001, and Swiss Madison Sublime II.

1.6 GPF -- Federal Standard Maximum

Still widely sold and appropriate for older drain lines with long horizontal runs, the 1.6 GPF tier gives an extra 0.32 gallons of water per flush compared to 1.28 GPF. In a household of four flushing eight times each per day, that adds up to roughly 10 extra gallons daily -- not trivial, but also not catastrophic. Models in this tier include the American Standard Champion 4, TOTO Drake (original), Gerber Avalanche, and most builder-grade toilets. MaP scores at 1.6 GPF tend to be high because the extra water volume helps clear the bowl even with less-optimized trapway geometry.

Dual Flush -- 0.8/1.28 or 1.0/1.6 GPF

Dual-flush toilets let users select a low-volume flush for liquid waste and a full flush for solid waste. The most common pairings are 0.8/1.28 GPF (TOTO Aquia IV, Woodbridge T-0001 dual-flush version) and 1.0/1.6 GPF (some Kohler and American Standard lines). Average consumption depends entirely on usage patterns. Assuming three liquid flushes for every one solid flush, a 0.8/1.28 GPF toilet averages about 0.92 GPF, versus 1.28 GPF for a single-flush HET model. The real-world savings over 1.28 GPF are modest; dual flush shines most against 1.6 GPF single-flush baselines.

How Do Popular Toilet Models Compare by GPF and MaP Score?

MaP scores sourced from map-testing.com published test results. Scores reflect maximum listed value for each model/SKU family. Winner row = best balance of low GPF and maximum MaP score.

How Much Water and Money Do You Save Switching GPF Tiers?

The math on GPF savings is straightforward but worth spelling out clearly because marketing materials often use idealized numbers. The calculation below uses a four-person household flushing five times per person per day (20 total daily flushes), which aligns with EPA household use estimates.

Dual-flush average assumes 3 liquid flushes for every 1 solid flush. Savings calculated at 20 flushes per day, 365 days.

Many water utilities in water-stressed states -- California, Arizona, Texas, Nevada, Georgia -- offer rebates of $50 to $200 per toilet for switching from 1.6 GPF to a WaterSense-certified 1.28 GPF model. In some cases those rebates exceed the cost difference between a mid-grade 1.6 GPF toilet and its 1.28 GPF equivalent. Always check your local utility's rebate portal before purchasing.

Does Lower GPF Always Mean More Clogs?

The clog-prone reputation of low-flow toilets originates from first-generation 1.6 GPF models introduced in the mid-1990s. Manufacturers simply reduced water volume in tanks designed around 3.5 GPF flushing dynamics. The flush valve was still 2 inches, the trapway still a 1 3/4-inch passage, and the rim wash still distributed water inefficiently around the bowl. The result was predictable: waste did not clear on a single flush, leading to double flushing, which eliminated the water savings and drove consumer frustration.

Modern toilet design addresses clog resistance through three primary mechanisms. First, larger trapways -- the American Standard Champion 4 uses a 2 3/8-inch trapway, the largest of any gravity-fed residential toilet -- physically allow larger waste to pass without snagging. Second, larger flush valves (3-inch canister or tower valves in Kohler's AquaPiston design, versus the older 2-inch flapper) release water faster, creating greater hydraulic force even at lower total volume. Third, directed water jets -- TOTO's Double Cyclone and Tornado Flush systems use two or three nozzles aimed at the bowl surface rather than a rim-wash channel -- create a centrifugal action that cleans the bowl while pulling waste into the trapway more efficiently.

The practical result is that 1.28 GPF toilets from TOTO, Kohler, American Standard, and Gerber routinely score 800 to 1,000 g on MaP tests while complying with WaterSense. For the vast majority of residential plumbing setups -- drain lines with standard 1/4-inch-per-foot slope, drain diameters of 3 to 4 inches, and runs under 30 feet -- a 1.28 GPF WaterSense toilet with a MaP score above 500 g will not clog more than its 1.6 GPF counterpart.

The exception is pressure-assist technology. Models like the Gerber Avalanche Elite use compressed air stored in a vessel inside the tank to blast water into the bowl at high velocity. These toilets can reach 1,000 g MaP at 1.0 or 1.1 GPF, but they are louder, cost more to repair, and require minimum water pressure of 20 to 25 PSI at the supply line. They are a strong choice for commercial restrooms or residential installations with confirmed drain slope issues, but they are not the default recommendation for typical homes.

For a deeper look at how flush technology affects real-world performance, see the comparison in best flushing toilets and the detailed 1.28 GPF vs 1.6 GPF breakdown.

Which GPF Rating Is Right for Your Home?

Standard Residential Plumbing -- 1.28 GPF

Drain lines installed to code after 1990 typically have a 3 to 4 inch diameter and a slope of 1/4 inch per foot. In these setups, 1.28 GPF toilets with strong MaP scores perform identically to 1.6 GPF models in practice. The water savings are real and the utility rebates in many states make the choice even easier. Recommended models: TOTO Drake II, TOTO UltraMax II, Kohler Cimarron, American Standard Cadet 3 FloWise.

Older Homes With Long Drain Runs -- 1.6 GPF

Pre-1960 homes sometimes have cast-iron drain lines that sag over time, reducing the effective slope below 1/4 inch per foot. In these cases, the extra kinetic energy from 1.6 GPF provides meaningful insurance against slow drains. If you are not certain of your drain condition, have a plumber snake or camera the line before committing to 1.28 GPF. Recommended models: American Standard Champion 4, TOTO Drake (G-Max), Gerber Viper.

Water-Stressed Regions and Green Builds -- Dual Flush or 1.0 GPF

In areas with tiered water pricing or mandatory conservation targets, a dual-flush toilet like the TOTO Aquia IV or the Woodbridge T-0001 in its dual-flush configuration squeezes out an additional 20 to 30 percent reduction versus a single-flush 1.28 GPF model on a per-flush basis, assuming typical 3:1 liquid-to-solid flush ratios. Pressure-assist at 1.0 GPF (Gerber Avalanche Elite) is another option where noise is not a concern.

Commercial and High-Traffic Installations -- Pressure Assist 1.0 to 1.1 GPF

Commercial restrooms with high daily flush counts benefit most from pressure-assist models that maintain consistent clearing performance across hundreds of daily flushes without adjustment. However, these require consistent water supply pressure and should be installed with service access in mind, since the pressure vessel is more complex to service than a standard gravity-feed flush valve.

How Does the EPA WaterSense Program Certify GPF Ratings?

The WaterSense program was established by the EPA in 2006 as a voluntary partnership and labeling initiative, modeled after the Energy Star program. For toilets specifically, the program has been one of the most measurable water conservation successes in residential history. As of 2025, EPA estimates that WaterSense-labeled toilets have saved more than 1 trillion gallons of water since the program began -- a figure that includes both residential and commercial installations.

Certification requires manufacturers to submit units to an EPA-recognized third-party certifying body. The testing protocol follows the MaP procedure: multiple test units from the same production run are tested at the labeled GPF, and results are averaged. The toilet must clear 350 grams of waste in a single flush every time to pass. Models that pass are listed in the WaterSense product search and may carry the WaterSense label on packaging and in marketing materials.

One nuance worth understanding: WaterSense certification is done at the model SKU level, not across a brand's entire toilet line. A manufacturer can sell WaterSense-certified models alongside non-certified 1.6 GPF models. The Champion 4 from American Standard at 1.6 GPF does not carry WaterSense certification (it exceeds the maximum GPF for eligibility), but American Standard's Cadet 3 FloWise at 1.28 GPF does. Always verify the specific model SKU against the WaterSense product list at epa.gov/watersense, not just the brand name.

For a related look at what MaP scores mean in practice and how they translate to real-world flush performance, see how MaP flush test scores work.