What is GPF in Toilets?

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I was sitting on the toilet the other day when I encountered some trouble with flushing. Slightly panicked, I lifted up the lid of the toilet tank and tried to figure out what was wrong.  The words GPF were written across the tank’s back wall and that got me researching on the spot.

What is GPF in toilets? Short for Gallons per Flush, GPF is the amount of water used by a toilet. A toilet’s GPF is the indicative figure of its water-efficiency. Federal standard GPF rate for toilets in the US is 1.6 GPF but there are higher efficiency toilets with 1.28 and 0.8 GPF sold today

Choosing a toilet with the ideal GPF can help you save money in the long run. So if you’re looking to save on your water bill or to replace your old toilet, you’ve come to the right place.

What is GPF in toilets?

GPF tells you how much water is consumed by your toilet every time you flush. This information is usually stamped behind the seat hinge of the toilet bowl.  If this is not the case, lift up the lid of your toilet tank and look for the manufacturer’s date stamp. This information alone can already tell you how much water is used by your toilet every time you flush. Below is a table summarizing the water consumption of toilets base on their manufacturing date:

Typical Toilet Water Consumption base on Manufacturing Date
Year of Manufacture Gallons per Flush
1982 and earlier 5-7 GPF
1982-1990 3.5 GPF
1990-1994 1.6 – 3.5 GPF
1994 – present 1.6 GPF
2005 – present 1.28 HET


Old toilets are usually less efficient than new ones. In 1994, the U.S. Congress established a national toilet standard of 1.6 GPF to encourage water conservation.  As of this writing, the figure remains the rule for toilets. New technology, however, has allowed manufacturers to offer more efficient models, with some even marketed as having a GPF of 1.28 or less. These toilets with low GPF are called High Efficiency Toilets (HET) by today’s standards.

What is the Best GPF for a Toilet?

The best GPF for a toilet is the one that consumes the least amount of water while still being able to remove solid waste with a single flush. The federal law states this as 1.6 GPF for all toilets that are currently sold on the market. More water-efficient models, however, are available on the market nowadays. These toilets have GPFs ranging from 1.28 to 0.8. While these fixtures use less water, the design of their system dictates how successful they are in flushing out the waste.

In the US, states have different requirements when it comes to residential toilets. Nevada, Washington, New York and Connecticut maintain the 1.60 national standard. California, Colorado and Texas, however, require homeowners to install toilets with 1.28 GPF or less. Georgia requires homeowners to install toilets with a WaterSense stamp, which have a minimum requirement of 1.28 GPF.

What is a 1.6 GPF toilet?

Toilets which follow the standard requirement of 1.6 GPF are usually single flush toilets. This toilet has been the manufacturing standard since 1994 due to the Energy Policy Act. Toilets which has this water efficiency figure has been generally reported to clear solid wastes, even massive ones, with a single flush. They are also reported to have less clogs and stains as compared to toilets which use less GPF.

This kind of toilet is widely available on the market, but each brand performs differently. Generally speaking, Toto, Kohler, and American Standard are considered the dependable brands. Some lesser-known ones such as Niagara and Saniflo, however, offer competitive performance and lower costs.

Do 1.28 GPF toilets work?

1.28 GPF toilets are water-efficient fixtures that can still perform the regular functions of a 1.6 GPF toilet. They have been available in the market since the early 2000s. These kind of toilets are the ones the Environmental Protection Agency (EPA) stamp with the WaterSense seal. They reduce water consumption by 20-60%. That translates to a savings of 13,000 gallons of water and $140 in costs per year.

In terms of performance, 1.28 GPF toilets have more difficulty in flushing out solid wastes. Sometimes, it takes more than one flush to eliminate a large mass and more effort to remove stains. New models, however, have been improved to match the performance of their 1.6 GPF counterparts. Pressure-assisted toilets, in particular, consume less water because it uses air compression to push out wastes.

1.28 vs 1.6 GPF toilets

1.28 GPF and 1.6 GPF toilets differ in terms of performance, water efficiency, and energy savings.

When it comes to performance, the 1.6 GPF is reportedly more capable of flushing down solid wastes. It also results to cleaner bowls and less clogs. The 1.28 GPF toilets, meanwhile, are also able to flush down wastes although sometimes you need to push the button twice. They also have more cases of clogs and drain problems compared to their 1.6 GPF counterparts. New models, however, have reportedly better performance and are endorsed by government agencies.

In terms of water efficiency, the 1.6 GPF uses more water to flush out wastes compared to the 1.28 GPF version. This translates to approximately 2,920 gallons of water consumption for the average flusher per year. By contrast, the 1.28 GPF toilet uses 2,336 gallons of water per year for the average flusher. This means that each person can save about 584 gallons per year if he or she uses the 1.28 GPF toilet. Imagine the amount of water that can be saved for a typical household of five people or more.

3.5 GPF Toilets

While they were the norm during the 1980’s, 3.5 GPF toilets are not commercially available anymore in the US. Despite this limitation, some people still prefer older models. This is because they tend to clean toilet bowls quite well and produce little odor.

If you’re determined to retain or install a 3.5 GPF toilet in the bathroom, the first thing to do is to check your local code. While the Energy Policy Act of 1992 bans the sale of high-capacity toilets, technically it doesn’t prohibit installing them. Still, it would be wise to check if your city has stringent rules about toilets.

You can actually purchase a 3.5 GPF toilet and have it shipped from abroad. Several Canadian distributors such as Plumbateria can do this, although this might turn out pricey. A more practical option would be to acquire a pre-used toilet. While this might raise a few eyebrows, toilets can be disinfected. Their parts are also made to last. If efficiency is an issue, you can always get a dual-flush valve kit.

If you’re into DIY, you can install your 3.5 GPF toilet as described in freeexistence.org, or you can go the safe route and hire a plumber instead. Whatever you choose, make sure to test your new 3.5 GPF toilet for leaks once it has been installed.

How much water is needed to flush a toilet?

The water consumed by your toilet depends on its GPF. If your toilet is an old model and uses 3.5 gallons per flush, each person can end up flushing away 17.5 gallons per day. This figure is based on 5 flushes, the average number of times a person uses a toilet.

Standard 1.6 GPF toilets, meanwhile, translate to 8 gallons of water per person per day. Lastly, the high-efficiency toilets with 1.28 GPF will only lead to a total of 6.4 gallons of water consumption per person.

Generally speaking, the high-efficiency toilets can flush just as well as their older counterparts. This is because manufacturers today also factor in air pressure, trapway size, and other innovative features in their design of toilets to make flushing easier.

What is LPF in toilets?

As an alternative way of measuring water consumption, LPF or liters per flush can be used. This scheme is more commonly used in countries where people employ the metric system such as the UK and Australia. GPF, however, is more prevalent in US and Canada. Either way, both are acceptable ways to measure water used by a toilet. The table below is a summarized conversion chart between the 2 systems:

Typical Water Consumption of Toilets
Metric (LPF) English (GPF)
13.2 LPF 3.5 GPF
6.0 LPF 1.6 GPF
4.8 LPF 1.28 GPF
3.8 LPF 1.0 GPF


Related Questions

How much does it cost every time you flush the toilet?

Flushing a toilet actually costs more than most people think. Besides the water consumed by flushing, you would also have to factor in the cost of sending the waste water through the sewers.

The average cost of water per 1,000 gallons in the US range from $1 to $5. Meanwhile, the average cost of sewer services per 1,000 gallons in the US range from $2 to 6$. Considering these figures, flushing the federal standard 1.6 GPF toilet would cost less than 2 cents per flush.

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