Gallons Per Flush Comparison (1.28 vs. 1.6 GPF)

Toilets vary in the amount of water they need per flush. GPF, or gallons per flush, is the unit used to measure and indicate the amount of water each toilet uses. The difference is less than half a gallon, however, choosing one style of toilet over another can have a lasting impact.

GPF often leaves consumers wondering about their BMs – does less water per flush lead to needing to use more than one flush? Do high efficiency toilets erase the evidence left behind? With changes in environmental legislation and advances in toilet technology, consumers need not flush their dreams away of being both efficient and effective.

1.28 GPF Low Water Consumption

white toilet for low 1.28 gpf consumption toilets, 3 photos one with blu water in bowl

1.28 and 1.6 GPF toilets are classified as low-water consumption units. These units were introduced in 1994 when American President George H.W. Bush signed the Environmental Protection Agency (EPA) into law. This law demands that toilets not use over 1.6 gallons of water per flush.

Historically, toilets required as much as 4 gallons of water or more (, which leads to a waste in both water and money.

This new restriction motivated many toilet manufacturers to rethink their current designs, as most toilets used over 1.6 gallons per flush at the time.

As some toilets required more than one flush to remove all waste, manufacturers need to find a solution to make low water consumption more effective and efficient.

Manufacturers met EPA guidelines by creating a toilet that uses less than 1.28 GPF by implementing larger flush valves and by redesigning the bowls. 

Changes in Technology and Design

white toilets that are high efficient water consumption, text included

To meet EPA guidelines, manufacturers added a larger flush valve to their units. A larger flush valve creates greater force, which directly improves flush efficiency. Toilet bowls have also been redesigned to feature technologies that help maximize the flush itself. Instead of having rim holes, newer models have two nozzles at each side of the bowl to create a powerful siphon action.

Toilet flapper flush valves have also been swapped out for canister flush valves. These allow water to flow to the tank from an angle of 360 degrees. 

Some toilets also have pressure vessels, which compress air and force water at a higher rate of speed.

1.28 vs. 1.6 GPF Differences

The primary difference between these two types of units is their flushing power. However, the flush volume does not necessarily mean that 1.6 GPF units are more powerful.

differences of 1.28 and 1.6 gpf toilet images with text in the middle, all three white toilets

Two Models Compared

To highlight the differences in these two types of units, let’s compare the TOTO Ultramax (1.28 GPF) and the American Standard Champion 4 (1.6 GPF).

TOTO Ultramax II American Standard Champion 4
GPF (gallons per flush): 1.28 1.6
Flushing System: Dynamax Tornado Flush Champion 4 Flushing System
Flush Type: Single Single
Style: One-Piece  One-Piece

While very similar, the TOTO Ultramax II is more efficient, saving 0.32 gallons of water with each flush. In doing so, you will use 20% less water. You can save over $100 per year using a 1.28 GPF toilet over a 1.6 GPF model. With the Ultramax II, you can save both money and water without compromising performance.

Several Pros and Cons

There are several pros and cons to both styles of toilets – 1.28 GPF units, and 1.6 GPF units. Each has their benefits and downfalls. Let’s take a closer look at the two. 

white toilets 1.28 or 1.6 gpf, brown toilet lid, white colored toilets

1.28 GPF Toilets

Pros Cons
Use less water May require more maintenance 
Cost efficient 

1.6 GPF Toilets

Pros Cons
Effective, strong flush Can be loud
Maintenance less common Uses more water 
Increased cost 

Use caution when looking to purchase a 1.28 GPF toilet, as only the most popular brands (TOTO and American Standard) carry the most efficient models. Other manufacturers do not typically implement high-end flushing technologies, meaning you may need to utilize two flushes to eliminate all waste.

Frequently Asked Questions

Are 1.6 GPF Toilets Allowed in California?

1.6 GPF toilets are not available in California, due to the California Energy Commission. All units sold within the state must use 1.28 gallons of water per flush or less.

What’s the Highest GPF Toilet?

Most toilets today use up to 1.6 gallons per flush. However, some older models can use as much as 4 gallons or more, which leads to lots of money wasted at the end of the year, especially if you live in a large family.

Do High-Efficiency Toilet Save Money?

Yes – as discussed, by consuming 20% less water with each flush, you’ll save on your water bills every year. Further, depending on your location, you could be eligible for additional rebates through the EPA’s WaterSense program.

Final Verdict

1.28 GPF toilets have several advantages. If you are in the market for a quiet, eco-friendly toilet that uses a minimal amount of water without sacrificing performance, a 1.28 GPF model is an excellent choice.

If you are unable to find a 1.28 GPF model from a top brand (TOTO or American Standard), it may be worth considering a 1.6 GPF model if flush efficiency is not a priority for you.