Toilet GPF Meaning & How To Choose Best GPF Toilet – Explained

What does GPF mean and why is it important to your toilet? Believe it or not, it’s the law! Your toilet is covered by federal and possibly local regulations that mandate the GPF rate your toilet needs to have. So let me share with you all I have learned about toilet GPF. This information might change the way you view a toilet.

What does GPF mean in toilets? GPF means Gallons Per Flush. It is the unit of measurement used for rating a toilet’s water consumption per flush. Since 1992, a maximum of 1.6 GPF is the Federally mandated standard toilet GPF rate. States with water efficiency standards like Califonia mandate a lower flush rate of 1.28 GPF.

The GPF water consumption rate for toilets has decreased over time. If your current toilet was made in the 1980’s or early 1990s, it most likely uses 3.5 GPF to 7 GPF!

Why is Toilet GPF or Water Consumption Rate Important?

Your toilet consumes the most amount of water in your house. According to studies, around 30% of the average American household water consumption is flushed down the toilet daily. So, federal, state, and local governments regulate toilet GPF rates, because the potential for water savings is huge.

The Water Research Foundation report found that toilet flushing frequency per person per day is 5 flushes. And, according to the EPA, installing a lower GPF toilet can reduce toilet water usage by 20 to 60 percent. This means you can save nearly 13,000 gallons of water per year.

If all the old and inefficient toilet in the United States was replaced with water-saving toilets, the savings would be around 520 billion gallons of water per year!

But, what is important when purchasing a new toilet is sorting out the best GPF rate. So keep scrolling and make your toilet investment worth it.

What is the Best GPF for a Toilet?

After reading the above you might think the toilet with the lowest GPF is the best toilet to buy. But the lowest GPF is not always the best. There are some low GPF toilet models that don’t flush well or cause clogging issues due to bad toilet design. So when you get a toilet you need to look into the GPF as well as how well it flushes and cleans the toilet bowl.

In the market today, there are both 1.6 GPF toilets and 1.28 GPF toilets. Both these GPF rated toilets have many very good toilet models as well as a few bad models for sale. So you need to be careful when choosing one. (That’s why picked and listed the best 1.28 GPF toilet in this page, and the best 1.6 GPF toilets in here.)

There are also a handful of ultra-high efficiency toilets with even lower GPF rates like 1 GPF and 0.8 GPF. 1 GPF and 0.8 GPF toilets use very new and still evolving toilet technology. So toilets that flush well with 1 GPF or a lower amount of water are very few and very expensive. (See Japanese Toto Neorest toilets)

In addition, there is also a type of toilet called the dual flush toilets. These offer two different GPF rates to choose and flush for solid and liquid waste. Most dual flush toilets in the current market offer 1.6 GPF for the full solid waste flushing and 1 GPF to 0.8 GPF for flushing liquid waste. (See our best dual flush toilet guide for more information.)

In most cases when you buy a toilet you will have to decide whether you are going for a 1.6 GPF toilet or a 1.28 GPF toilet. So it’s important to know more about these two GPF rates. Let’s check out 1.6 GPF toilets first and then 1.28 GPF toilets.

What is a 1.6 GPF Toilet

1.6 GPF toilet was the first popular “low flow toilet” that flushed at a rate of 1.6 gallons of water per flush. They were first developed and introduced in the early 1990s when the 1.6 GPF federal standard for toilets was mandated. Now no toilets that use more than 1.6 GPF can be manufactured or sold.

Early 1.6 GPF toilet models had flushing and clogging issues due to bad design. They got good consumer reviews only after some major design improvements in the late 1990s. The improvements included larger trap-ways to prevent frequent clogging and larger flush valves to allow a more powerful flow of water to enter the bowl.

Unfortunately for 1.6 GPF, the continuous technology developments have now introduced High-efficiency toilets (HET’S). These toilets use a lesser GPF rate than the standard 1.6. But the common question is if it would actually do its job?

Let’s take a look with the most commonly used HET “1.28 GPF”.

Do 1.28 GPF toilets work?

Yes, they work just as expected. Independent tests show that the flushing efficacy of HET’s like 1.28 GPF toilets can evacuate up to 800 grams (1.75 pounds) of solids with every flush.

For this purpose, 1.28 GPF toilets use fast-action flushing technologies. The secret of these technologies is to move the water quicker from the tank to the bowl. As such, the speed and powerful force of water to entering the bowl will flush the waste thoroughly. This will leave a clean bowl with clear water without any tiny waste particles.

To ease your doubts, you can check for the “WaterSense” label in these toilets. The label is given only to water-saving toilets like HET’s that meets the standard criteria for performance and efficiency.

Or if you’re still reluctant on its performance, you can check for the “MaP” rating in these toilets. This rating reviews the “Maximum Performance” of HET models. Any MaP rating over 500 grams can work well and do its job at perfection.

So now to make the selection process easy for you, let’s do a little comparison between 1.28 and 1.6 GPF toilets.

1.28 vs 1.6 GPF toilets

We can make this comparison on the following 4 features,

1. Performance

1.28 GPF toilets use a powerful flushing technology and a supporting design. So only one flush would clear the waste contents, leaving a clean bowl with clear water. But when streaks hit the bowl directly you may have to flush twice.

Whereas, 1.6 GPF toilets have continued to show problems in their design incompatibility to meet the required level of performance. This will very often leave unclear water and waste contents in its first flush. And so wanting to flush twice or more and not benefit from the water saving feature.

2. Frequent problems

Both 1.28 and 1.6 GPF toilets have minor clogging issues due to less water usage during the flushing process. Less water means (not always) there is not enough water to move solid waste out into the sewer system. And so the solid waste builds up in sewer lines clogging the toilet.

Yet, this complaint is made often in 1.6 GPF toilets as it uses a less powerful flushing technology than 1.28 GPF toilets. But when flushing in 1.28 GPF toilets, the powerful force of water helps to push down the waste into the sewer system easily.

3. Interior design

1.6 GPF toilets have easily usable interior design in many of its models over 1.28 GPF toilets. You can identify this using the water surface area of these two toilet bowls.

Many 1.6 GPF toilet models have a larger water surface area, allowing to keep more water in the bowl. So when using, the waste will directly settle in the water and can be easily flushed along with the water itself, leaving the bowl clean.

But, recent HET’s like 1.28 GPF toilets have a small water surface area, allowing very little water to stay in the bowl. So as you can guess, the solid waste is more likely to be striking the bowl (porcelain). This will leave streaks and skid marks in the bowl with an unpleasant odor. So you will have to flush twice or more, or at worst use a brush to clean the mess.

4. Water and cost savings

On average switching from an old toilet (manufactured before 1992) to a 1.6 GPF toilet can save 6,935 gallons of water and 41.61 dollars annually. Whereas the same switch to a 1.28 GPF toilet on average can save 8,103 gallons of water and 48.62 dollars annually.

However, as discussed above both 1.6 GPF and 1.28 GPF toilets face minor problems, wanting to flush twice or more. In such situations, these savings won’t be achievable.

By now you can see that both 1.28 GPF and 1.6 GPF toilets have their own goods and bads and it’s hard to pick one best. Also, remember the above comparison depends and differs based on toilet brands. Best toilet brands such as TOTO and Kohler have reported very few to rare complains in its 1.6 GPF or 1.28 GPF toilets. But they are comparatively expensive.

So if you’re stuck between the two GPF rates, get hold of a dual flush toilet. This toilet lets you choose between two flushes. On average a dual flush toilet uses 0.8 GPF for liquid waste and 1.6 GPF for solid waste. But if you forget to use it, the whole water (Eco-friendly) and cost-saving benefit will be vain.

Talking about water and cost savings, you won’t believe the GPF rates old toilets had. Take a look….

3.5 GPF toilet

This is an old standard flushing rate that uses 3.5 gallons per flush using a gravitational force. Toilets manufactured between 1980 to 1992 used this flush rate. 3.5 GPF on average means 18.8 gallons of water flushed daily. So that’s a lot of water and dollars down the drain.

In fact, before the 1980s toilets had a flushing rate of 5 to 8 GPF that adds to an average of 48 gallons of water down the drain daily. Even today, some of these toilets are still in use in old houses and buildings.

Now with different GPF rates bubbling in your head, you surely might be looking for the next question.

How much water is needed to flush a toilet?
If you’re going to flush a toilet manually you will need an average of 2-5 gallons of water depending on the waste. But this amount can reduce when the force of water dumped into the bowl increases.

This is exactly what happens in flushing technologies. The powerful force of water reaching the bowl when flushing, makes it easy to push the waste with less water. So sometimes, even a powerful dumping of 2-3 gallons of water into the bowl can flush a toilet out of any waste.

And as we reach the end, I’ve got a fact booster for you.

What is LPF in toilets?

LPF in toilets means “Liters per flush”. This is a flush rate that shows how much water a toilet uses in liters when flushing. LPF don’t differ anywhere compared to GPF. It is only a way of displaying the “water usage rate” of toilets to countries where liters are the common way of liquid measurement. Countries such as Canada, Australia, India, and Sri Lanka use liter measurements. I also did some quick conversions for your understanding

• 5.0 GPF = 19 LPF
• 3.5 GPF = 13 LPF
• 1.6 GPF = 6.0 LPF
• 1.28 GPF = 4.8 LPF

Related Questions:

How much does a toilet flush cost?
On average each flush uses 1.6 gallons of water. And one gallon of water on average costs 3/10th of a cent in the US. So a toilet flush costs 1/2 cent or US$ 0.005.

About Reema Rizwan

Reema Rizwan is one of our dedicated home improvement researcher and writer. She is also a business management undergraduate. She writes research-based articles on home improvement topics to help our readers save time in getting all the information they need to solve their home improvement needs. In her spare time, she enjoys cooking, baking and reading niche topics.

View all posts by Reema Rizwan →

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