1.28 GPF vs 1.6 GPF Toilets: Pros, Cons & Examples

Last Updated on May 18, 2022 by toilethaven

One of the main thing almost all toilet buyers look out for when buying a new toilet is the flushing power. We all hate flushing twice. Or even thrice.

It is even better if you can buy a powerful flushing toilet which is also water efficient. Most toilets sold today in the United States are rated as either 1.28 GPF or 1.6GPF. So, what is the difference between 1.28 GPF and 1.6 GPF toilets? Is one better than the other?

A 1.28 GPF toilet uses 1.28 gallons of water per flush while a 1.6 GPF toilet uses 1.6 gallons per flush. 1.28 GPF toilets are therefore more water efficient than 1.6 GPF toilets but none is necessarily better at flushing than the other.

A toilet’s flushing power is dependent on so many other factors and not just their water consumption. Some 1.6 GPF toilets flush better than some 1.28 GPF toilets and vice versa.

For people whose primary objective is a water efficient toilet, a 1.28 GPF toilet is the best option. If you however want a powerful flushing or both a powerful flushing toilet and a water efficient one, you might need to do more research.

Introduction of Low-Flow Toilets

Both 1.28 GPF and 1.6 GPF toilets are considered to be low-flow toilets. Toilets in the US have however not always been low-flow. So, when did they came about?

Low-flow also known as low-flush toilets were introduced in January of 1994 for residential buildings and January of 1997 for commercial buildings after President Bush had signed the Energy Policy Act into law in 1992.

The law demanded that toilets sold in the United States should not use more than 1.6 gallons per flush. Before then, most toilets used 3.5 gallons per flush or even as much as 7 gallons.

Can we then say that toilets flushed better then than they do today? Not at all. Most toilet tanks were actually mounted high up the wall to give the water more force as it dropped to the bowl and hence a stronger flush.

The first models of low flow toilets were however bad at flushing. One needed to flush them more than once to clear everything.

Toilet manufacturers went back to the drawing board to see how the flushing power of low flow toilets could be improved. And they did.

The toilet manufacturers discovered that toilets could use even less water than the 1.6 GPF stipulated by the federal government and that is how 1.28 GPF toilets came to be. Today there are many toilets using less than 1.28 gallons per flush but still flush powerfully.

So, what are some of the changes that improved the flushing power of the initial low-flow toilets? Here are some:

1. Bigger Flush Valves

The flush valve is the opening at the bottom of the toilet tank where water leaves the tank and enters the bowl during flushing. The rate at which water enters the bowl (its force) determines the toilet’s flush power.

A bigger flush valve means water enters the bowl more forcefully resulting in a stronger flush. Older toilets have a small flush valves (2 inches) which means the flushing process takes longer and are hence not as powerful.

The best flushing low flow toilets have a 3-inch or even 4-inch flush valve. An example in each case is the Toto Ultramax II (1.26 GPF) with a 3-inch flush valve and the American Standard Champion 4 (1.6 GPF) with a 4-inch flush valve.

2. Redesigning the Bowl

In older toilets, water from the tank would enter the bowl through rim holes located all around the rim. This design does not provide for better bowl scrubbing and rinsing.

Toto invented the tornado flushing system while American Standard came up with the VorMax flushing technology and PowerWash rims. These designs alters how water enters the bowl.

Instead of following a straight line like with ordinary rim holes. The water comes out through 2 powerful nozzles on each side of the bowl. Due to the sideways orientation of the nozzles, the water vortexes/whirlpools around the bowl scrubbing and rinsing it.

3. Flush Valve Redesign

Some toilet manufacturers like Kohler noticed that the toilet flapper was restricting water flow to the bowl to some degree. They ditched the flapper-type flush valve and came up with a canister flush valve.

The main advantage of a canister flush valve is that unlike a flapper flush valve, it lifts up completely allowing water to flow to the tank from a 360 degrees angle. This increases the rate at which the water enters the bowl and hence increasing the flushing power.

4. Pressure-Assisted Flushing

Pressure-assisted toilets are toilet with an extra tank inside the primary toilet tank, called a pressure vessel. Water flowing into the tank compresses the air inside the pressure vessel and is hence stored under pressure.

When you flush the toilet, the water is forced out under rapidly which as a result leads to a stronger flush. Pressure-assisted toilets are however louder than ordinary gravity flush toilets.

1.6 GPF Toilets Restrictions

1.6 GPF toilets cannot be sold in all the states. Some states have even tougher toilet water consumption regulations than those given by the federal government.

Effective January of 2016, the California Energy Commission (CEC) required that all new toilets sold in the state have a consumption of 1.28 gallons per flush or even less. 1.6 GPF toilets can therefore not be sold in California.

The states of Texas and Colorado later joint Texas in enforcing the same regulations. If you are therefore a resident in any one of this states then you can’t buy a 1.6 GPF toilet.

To further encourage people to move away from 1.6 GPF toilets and embrace 1.28 GPF and other ultra-high efficiency toilets, the United States Environmental Protection Agency (EPA) started a program called WaterSense.

WaterSense puts a label on water efficient toilets. Home owners looking to buy such toilets can therefore easily identify them.

WaterSense toilets have a consumption of 1.28 gallons per flush or even less. All toilets sold in California, Texas and Colorado are WaterSense-labelled.

1.28 GPF vs 1.6 GPF Toilets

So, what are the advantages and disadvantages of installing a 1.28 GPF toilet over a 1.6 GPF toilet and vice versa? Which toilet should you buy? Let us look at some of the influencing factors.

1. Flush Power

There are a lot of people who believe and say that 1.6 GPF toilets have a stronger flush than 1.28 GPF toilets. Is this the truth though?

Let us look at 2 high-end toilets, one with a consumption of 1.28 GPF and the other with a consumption of 1.6 GPF. The 1.28 GPF toilet is the Toto Ultramax II and the 1.6 GPF toilet is the American Standard Champion 4.

Both of these toilets almost cost the same amount of money and are both one-piece toilets. They are considered by most people as some of the best flushing toilets in the market. Is one among the 2 better at flushing toilet than the other?

Although the Toto Ultramax II is a 1.28 GPF toilet, it is more effective in waste elimination than the American Standard Champion 4 which is a 1.6 GPF toilet.

The tornado flushing system makes the Toto toilet a better flusher despite using less water than the American Standard Champion 4.

2. Water Efficiency

How much water does a 1.28 GPF toilet save over a 1.6 GPF toilet? Is it something that will make a difference in your wallet?

According to WaterSense, toilets are the main source of water use in homes accounting for 30% of the water usage. From my calculations, the difference between a 1.6 GPF and 1.28 GPF toilet is 0.32 gallons per flush.

This means that every time you use a 1.28 GPF toilet over a 1.6 GPF toilet you use 20 % less water. WaterSense estimates that you can save more than 90 dollars a year by using a 1.28 GPF toilet instead of a 1.6 GPF toilet.

To make even more sense out of this, let us see how much water an average American family of 4 would save in a year, assuming that each family member uses the toilet 5 times in a day. We have already identified that the difference between a 1.6 GPF toilet and a 1.28 GPF toilet is 0.32 gallons.

Multiply 0.32 gallons by 4 family members by 5 times a day then multiply the daily consumption by 365 days in a year. The answer is 2336 gallons.

A single family can save 2336 gallons yearly by choosing to install a 1.28 GPF toilet over a 1.6 GPF toilet. Billions of gallons can therefore be saved if all houses in America installed the water efficient 1.28 GPF toilets.

3. Cost

I do not think the cost of a toilet has anything to do with their water consumption. There are some 1.6 GPF toilets that are more expensive than some 1.28 GPF toilets and vice versa.

Many states and WaterSense partners will have however offer rebates when you buy a 1.28 GPF toilet (WaterSense-labeled) to incentivize more people to buy them. The rebates are not available for 1.6 GPF toilets.

Apart from the rebates, you will also save money in water bills when you install a 1.28 GPF toilet over a 1.6 GPF toilet. As we have already seen, water bills as a result of toilet usage will reduce by 20%.

4. Eco-Friendliness

Toilets with a high water consumption rate put a strain on our natural water resources. That is why the federal government abolished the 3.5 GPF toilets. California’s government also came up with even stricter regulations due to the droughts affecting the state.

It goes without saying that 1.28 GPF toilets are more eco-friendly than 1.6 GPF toilets. From our calculations, just one American family can save 2336 gallons water in a year by installing a 1.28 GPF toilet over a 1.6 GPF one.

For anyone looking to do their own small bit in protecting the environment then they should consider installing 1.28 GPF toilets.

Best 1.28 GPF Toilets

For anyone looking to install a 1.28 GPF toilet, there are so many options to choose from. I will however recommend 2 models which are in my opinion the best at flushing despite their low consumption.

One will be in the high-end region while the other will be a budget pick. These 2 are the best 1.28 GPF toilets in the market.

1. Toto Ultramax II



The Toto Ultramax II is a single flush one-piece elongated toilet. Here are some of its features and specifications:

  • One-piece toilet
  • Left-hand chrome trip lever finish
  • Tornado flush
  • EPA WaterSense labelled
  • Cefiontect glaze
  • Manual gravity flush
  • Soft close seat included
  • Elongated toilet bowl
  • Mounting bolts, wax ring and water supply line not included
  • One year limited warranty
  • Depth: 28.375 inches
  • Width: 16.625 inches
  • Height: 28.75 inches
  • 16.25 inch bowl height
  • Rough-in: 12 inches

To read more on the Toto Ultramax II and also see comparisons with other toilets check out this post I wrote earlier.

2. Kohler K-3999-0 Highline



The Kohler K-3999 Highline is a single flush two-piece elongated and comfort height toilet. Some of its features and specifications are:

  • Elongated toilet
  • 1.28 gallons per flush
  • Polished left-hand chrome trip lever
  • Single flush toilet
  • Class Five flushing technology
  • 12 inch rough-in
  • 3-bolt installation
  • Seat and supply line not included
  • 16.5 inch bowl height
  • Toilets dimensions: 29.75 x 18 x 31.25 inches
  • Vitreous china material
  • WaterSense labelled
  • Toilet bolt caps included
  • Floor mounted
  • Mounting bolts and wax ring not included
  • One year limited warranty

To read more on the Kohler Highline toilet and to also see its comparison with other toilets in the same range check out this post.

Best 1.6 GPF Toilets

There are some very good 1.6 GPF toilets in the market. As long as you are not in California, Texas or Colorado then you can buy this toilets.

Just like with the 1.28 GPF toilets, I have included one high-end toilet and one budget toilet. These are the 2 best 1.6 GPF toilets.

1. American Standard Champion 4



The American Standard Champion 4 has gone through continuous improvements since the first model was released. The newest model is a one-piece single flush elongated and comfort height toilet available in white, bone or linen.

Some of Champion 4’s features and specifications include:

  • Elongated toilet
  • One-piece toilet
  • 16.5 inch bowl height
  • Slow close toilet seat included
  • 1.6 gallons per flush
  • 4 inch piston action accelerator flush valve
  • 12 inch rough-in
  • EverClean surface
  • 2-3/8 inch glazed trapway
  • 118 pounds
  • Vitreous china material
  • Floor mounted
  • 10 year limited warranty
  • Mounting bolts and wax ring included
  • Matching toilet bolt caps included
  • Toilet dimensions: 29.5 x 16.75 x 29.75 inches

To see if the Champion 4 is the best toilet for you, check out more reviews about it as well as comparison with others in this post.

2. Toto Drake



The Toto CST744SL Drake is a one of the most popular toilets by Toto. It is a powerful flushing toilet and budget-friendly too. The following are some of the specification and features of the Toto Drake elongated bowl toilet:

  • 1.6 gallons per flush
  • Chrome trip lever finish on the left
  • Two-piece elongated toilet
  • G-Max flushing system
  • Single flush
  • Grazed trapway
  • Toilet seat not included
  • Mounting bolts and wax ring not included
  • Toilet bolts included
  • Gravity flush
  • Vitreous china
  • 12 inch rough-in
  • Floor mounted
  • 16.5 inch toilet bowl height
  • Toilet dimensions: 28.125 x 19.875 x 30.5 inches
  • One year limited warranty

You can find more reviews of the Toto Drake toilet as well as comparison with other toilets in this post I wrote earlier.

1.28 GPF and 1.6 GPF Toilets Alternative

You can actually decide to completely ignore 1.28 GPF and 1.6 GPF single flush toilets and go for a dual flush toilet. A dual flush toilet is a toilet with 2 water consumption rates.

It gives you an option to either use half a flush for liquids or a full flush for flushing solids. Most people use the toilet more times for the number 1 than for the number 2. You are therefore able to only use a little amount of water to flush the liquids which is more efficient than using the same amount of water for liquids and solids.

Most dual flush toilets are also WaterSense-certified and can hence be sold in California, Texas and Colorado. Dual flush toilets often have 2 buttons at the top of the lid instead of the usual trip handle.

The big button is for the full flush while the smaller button is for the half flush. Some dual flush toilets however have 2 flush handles, one for the full flush and the other for the half flush.

If you would like to read more on dual flush toilets check out this post. You will learn how they work and the best of them in the market.

How to Buy a Good Toilet

If you need to buy a great toilet, there are a few things that you will need to consider before making the purchase. Their flushing rate is important but there are other important factors too, such as the following:

  1. Type of toilet: You will need to choose either a one-piece toilet or a two-piece toilet. To learn more about the pros and cons of each check out this post.
  2. Shape of toilet bowl: In the United States toilets have either a round-front bowl or an elongated one. Read more here on the advantages and disadvantages of either.
  3. Toilet dimensions. The toilet you need to buy has to fit in the space you have at home. Some toilets are bigger than others while some are more compact. Apart from the obvious toilet dimensions, you will also need to be sure about their rough-ins.
  4. Color: Toilets these days come in so many colors and not just white. Black toilets like these ones are stunning.
  5. Brand: Toto, Kohler and American Standard are some of the biggest toilet manufacturers. Buying a toilet from one of this 3 gives you some sort of assurance since they are very reliable.

If you would like to read more on the factors to consider before buying a toilet, check out this post I wrote a days ago.

Final Words

1.28 GPF toilets seems to have more advantages than 1.6 GPF toilets. Residents in California, Texas and Colorado don’t even have a choice. The decision has already been made for them. If you are however outside of these states you can go ahead and buy your favorite 1.6 GPF toilet without a problem as long as your are satisfied with its other features and specifications.


1. What is the best 1.6 GPF Toto toilet?

The Toto Drake elongated and comfort height toilet is probably the best Toto toilet with a flush rate of 1.6 GPF. It is a powerful flushing toilet that is also competitively priced.

2. What is the best Kohler 1.6 GPF toilet?

Kohler Cimarron elongated and comfort height toilet is one of the best Kohler toilets with a flush rate of 1.6 GPF. It uses Kohler’s canister flush technology for a powerful flush.

3. What does 1.6 GPF toilet mean?

A 1.6 GPF toilet is a toilet that uses 1.6 gallons of water per flush.

4. What is the best 1.28 GPF toilet?

The Toto Ultramax II is one of the best 1.28 GPF toilet. It is a one-piece toilet with a comfort height and coated with Toto’s Cefiontect glaze. With a 3-inch flush valve and an extra-large trapway, it is a powerful flushing toilet despite its low water consumption

5. What is the best GPF for a toilet?

Toilets with a flush rate of 1.28 GPF are really good. They are water efficient, flushes well and can be sold all over the United States. 1.28 GPF toilets are WaterSense labelled, CEC and CalGreen compliant.

6. Is a 1.6 GPF toilet good?

Toilets with a flush rate of 1.6 GPF are more water efficient than older 3.5 GPF toilets. They are also powerful flushers. 1.6 GPF toilets however use more water than the required 1.28 gallons per flush in California, Texas and Colorado and cannot therefore be sold there.

7. Can I buy a 1.6 GPF toilet in California

No. According to the California Energy Commission (CEC) toilets sold in California cannot use more than 1.28 gallons per flush.

8. What does LPF mean in a toilet

LPF in a toilet means liters per flush. In the United States people however use GPF which means gallons per flush.