How Much Water do Low Flow Toilets Save?

A dual sink vanity with wood framed rounded mirror with low flow toilet next to it.

There are a lot of ways to save water at home. Since toilets account for approximately 30% of home water usage according to the EPA, one of the easiest and most effective ways to save water is with a low flow toilet.

Low-flow and high-efficiency toilets use only 1.6 or 1.28 gallons per flush respectively. For a family of 4, this can save 13,870-16,206 gallons (or even more if you have a toilet built before 1980) of water each year, depending on the toilet you are upgrading from.

Let’s Look at the Numbers and See How Much You Can Save!

If you’re considering replacing your toilet and want to know how much water it will save you it’s important to take into account how much water your current toilet uses and how many people are in your household.

Toilets that were manufactured before 1980 generally have a tank capacity of between 5 and 7 gallons. This means they use 5-7 gallons of water per flush. The standard toilets manufactured between 1980 and 1994 use 3.5-gallons per flush.

In 1995 the federal standards required all new toilets be manufactured to use no more than 1.6 gallons of water. That is considered a low-flow or low-flush toilet. High-efficiency toilets use no more than 1.28 gallons per flush. In some areas this is the new standard.

A pink 1950s large tank toilet in a pink tiled bathroom.
Circa 1950s Model – Using Approximately 7 Gallons/Flush

So you can see from the chart that if you are upgrading from a pre-1980 toilet to a low flow toilet with a family of 4 rather than using 100 gallons a day flushing (assuming your toilet uses 5 gallons per flush) you could use only 32 gallons per day to flush. That’s 68 gallons of water saved per day. Over the course of a year you’ll save 24,820 gallons of water.

Even if you are just upgrading from a 3.5 gallon tank to a 1.6 gallon tank with a family of 4 you’ll save 38 gallons each day and 13,870 per year. Go further to upgrade to a high-efficiency toilet and you’ll save 44.4 gallons of water each day or 16,206 each year.

You can use the chart to consider your own household and what the upgrade will amount to in saved water. If you aren’t sure how old your toilet is you can check the inside of the tank. Oftentimes it will be stamped with the date it was manufactured.

Save Money – Save The Environment!

This is obviously a win for the environment. Because seriously, when you think about it, using perfectly clean water to wash away our waste is really a waste. So many areas of the world don’t have enough clean water to drink and we’re busy doing our business in it and flushing it away like it was an unlimited resource with no value.

A toilet with cash in the water in the bowl

Using less water with every flush is also a win for your pocketbook if you have to pay for your water as many people do. According to a study completed at Michigan State University, water bills have gone up 41% since 2010.

In cities like Atlanta and Seattle households are paying as much as $300/month for water and wastewater services for a family of four. If you live in these areas you already know the bite of higher water prices. If you don’t, this story could be coming to a city near you very soon.

So if you and your family of 4 can save even 15,000 gallons a year painlessly by using a low-flow toilet it can put more money back in your pocket every month. If your toilet is older, you’ll save even more.

According to a CBS news report, Americans pay an average of $104/month for water and sewer. If 30% of your water usage is from flushing the toilet you could save $31/month. So your new toilet will pay for itself pretty quickly. And toilets generally last 20 years or more, so you’ll have a long time to enjoy the savings especially as water prices are only forecast to continue going up.

Pressure-Assist vs. Gravity-Flush

If you’ve heard that low-flow toilets don’t work as well, that’s old news. Since they were first developed they’ve come a long way and they have been redesigned to take care of waste much more efficiently than they originally did when designers just decided to make the water tank smaller rather than working to make the whole toilet more efficient.

After some false starts back in the 1990s low-flow toilets usually work as well as the standard 3.5 gallon or larger tanks.

What we think of as the “normal” home toilet is generally a gravity-flush, that relies on the gravity to bring water into the bowl and remove the waste.

There is also another type of toilet, the pressure-assist. This type of toilet relies on the pressure of the water supply to the toilet to compress air in an inner tank. Then when the toilet is flushed that pressurized water is forced into the bowl. This helps move waste out of the bowl and down the drain.

The pressure-assist toilet is generally a bit more expensive to buy and maintain, but if you have drainage problems in your home, it might be a solution to consider. (Your plumber can help you decide.)

Design matters!

The newer low-flow toilets work very well overall and have a high rate of customer satisfaction. To increase the toilet’s ability to do its job and efficiently remove waste, consider two additional points.

  1. Toilets that are a bit higher, like those compliant with ADA guidelines, actually work better because the water has further to fall from the tank and that will give the water more force to clear the bowl.
  2. Round bowls are easier for low-flow toilets to clear than elongated bowls because they are a bit smaller. So released water is more efficient at clearing waste.

Dual-Flush toilets vs. the WaterSense 1.28-gallon flush

You might be wondering about dual-flush toilets and if they are a better choice. And in case you aren’t familiar with them, these are the toilets that have one button to push for removing solids and another to push for a “light flush” using less water to remove liquids.

In some situations, dual-flush toilets might be a good choice, but when looking at reviews and reports it seems that customer satisfaction with dual-flush toilets isn’t nearly as high as with low-flow toilets. If you get a high-efficiency 1.28 gallon/flush toilet the water usage will be similar and the efficiency at clearing the bowl appears to be somewhat better. It’s hard to save water and money if you have to flush multiple times to do the job.


Low-flow and high-efficiency toilets not only work better than they used to, but they are also a bit more reasonable as far as price. You can get a high-efficiency 1.28 gallon/flush model for less than $140. The plumber’s cost for installation will be in addition to that of course.

If you are strong enough to move a toilet around (they are heavy) and want to give the installation a try yourself there are several YouTube videos that can help. This one is a This Old House guide for installing a toilet:

Rebates for Low Flow Toilets

Depending on what state you live in you may be able to get a rebate when you buy a low-flow toilet.

The EPA’s WaterSense site has a listing you can check out to see if there is a rebate available in your area. Some of the programs even cover low-flow showerheads and faucets as well.

A mostly white bathroom with a skylight.

The Cons

“Yes,” you might be thinking, “they save water and money – BUT are they as good?” Overall, yes, the new low-flow toilets are as good or even better at clearing waste from the toilet. But there are a couple of things that might be considered “cons.”

1. Because there is less water used sometimes waste isn’t removed from the bowl as effectively and additional flushes are needed. But as I mentioned, new designs work much better than the original ones did and you will likely not have problems with this.

2. If you live in an older home your pipes may not work as well with low flush toilet models which depend partially on the correct angle and slope of installed pipes to work at maximum efficiency. If your home is less than 20 years old you shouldn’t have a problem. But since most of the big inefficient toilets are in homes older than 20 years this is something to have your plumber take a look at.

3. Pressure assisted toilets, while they can ensure waste gets flushed efficiently, generally make a louder sound with each flush. This might not seem like a big deal, but if you’re trying to sleep and a loud toilet goes off in the bathroom next to you, this might be something you wish you would have considered.

Commercial bathrooms are more likely to have pressure-assisted flushes. So if you’ve used a bathroom at the movie theater or at a rest stop or something like that and the toilet was really loud when you flushed, it might be because it was pressure-assisted.

No Budget for a New Toilet?

If a new toilet isn’t in the cards because you’re renting or your pipes are not angled the correct way or you just don’t have the budget to afford an installation right now there are ways you can work with the toilet you have to make it more efficient.

Reduce the water used in each flush by adding something to the tank to take up some space. You can add a brick to the holding tank, but be sure that it’s wrapped tightly in a ziplock bag or else the brick will decay over time and might cause problems.

You can also add a water bottle filled with sand to weigh it down to your tank. The size will depend on the size of your tank and how much water you need to get a flush that works without having to flush multiple times to clear the bowl. You may need to experiment with this a bit.

Be sure your toilet is working at peak performance. Check for leaks by placing a few drops of food coloring in your toilet’s tank and then wait ten minutes without flushing. If the color shows up in the bowl that means you have a leak.

Fixing a Leaky Toilet

Here’s a great video from the EPA that shows how you can replace a faulty toilet flap which is generally the problem that causes leaks.


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