Many people don’t realize that toilet flushes are one of the biggest water wasters in the home. Though the Environmental Protection Agency (EPA) has limited the maximum water usage per flush to 1.6 gallons for modern toilets, even this amount can still add up—especially if multiple people live in your home.
The exact amount of water your toilet uses per flush depends on its design, age, and whether it meets modern water-efficiency standards. Let’s take a closer look at some of the main factors that determine your toilet’s water usage.
Key Points
- Toilets are typically the biggest water consumers in the home, so toilet water efficiency matters! Upgrading to a modern toilet is a great way to reduce water usage.
- Federal standards dictate that modern toilets must use no more than 1.6 gallons of water per flush. WaterSense toilets save even more, using no more than 1.28 gallons per flush.
- Proper toilet maintenance helps optimize water usage. Inspecting and replacing flapper valves and fill valves can address issues like frequently running toilets and weak flush power. Be aware of the signs of toilet leaks, which also contribute to water waste.
- Eco-friendly toilet options are available, like gravity-assisted models that avoid additional energy consumption and dual-flush options that allow you to choose how much water to use per flush.
Factors Affecting Toilet Water Usage
It takes force to remove waste from a toilet bowl, which is the main reason toilets use so much water. The exact amount of water per flush depends on what kind of toilet you have, the water pressure in your toilet and home, and your toilet’s valve type. Let’s discover how each of these factors affects a toilet’s water usage.
Toilet Design
Toilets come in two main styles: gravity- and pressure-assisted. Gravity-assisted models are the most common type, and they work by drawing water from the tank into the bowl through an opening near the bottom of the bowl known as the “S” trap.
Flush type can also influence a toilet’s water usage. Many toilets have a single flush, meaning they’ll use a predetermined amount of water for each flush. Dual-flush toilets allow users to choose between a full or partial flush depending on how much waste they are removing from their bowl.
WaterSense Certification
The WaterSense program was created by the EPA to help consumers choose water-efficient products like showerheads, faucets, aerators—and, of course, toilets!
To receive a WaterSense certification, a toilet model must use no more than 1.28 gallons of water per flush (that’s 20 percent less than the federal standard!). Certified toilets must also meet the EPA’s standards for performance, ensuring each WaterSense throne saves water and packs an efficient flush.
Though it may seem costly to replace your older toilet with a WaterSense model, it’s a worthwhile investment for most households. Making the upgrade to a WaterSense-certified toilet can save you almost 13,000 gallons of water a year—that’s around $170 off your annual water bill total!
Water Pressure
A toilet’s water pressure is measured in pounds per square inch (PSI) and is influenced by the overall water pressure in your home. Low-flow toilets use less water because they have a lower PSI than conventional toilets—but their effectiveness can be impacted by your home’s water pressure.
If you live in an older home with high water pressure (over 50 PSI), installing a low-flow toilet may not save you as much money as expected. This is because there will be more force behind each flush, reducing the effectiveness of the low-flow toilet. A plumber or contractor can check your home’s PSI and make adjustment recommendations to maximize efficiency.
Type of Valve
The type of valve or fill valve in your toilet can make a significant difference in how much water it uses. There are two common types: ballcock valves and electronic fill valves (EFV).
Ballcock valves are common in older toilets and come in two models:
- Gravity-fed systems: These simple systems typically use less water since they rely on gravity to move water from the tank to the bowl. They are typically considered the more water-efficient type.
- Pressure-assist systems: These models are usually less water efficient since they require incoming water pressure to forcefully flush the bowl. They are highly effective for clearing waste but use more energy and, therefore, create more greenhouse gas emissions.
Electronic fill valves (EFVs), on the other hand, are state-of-the-art mechanisms that electronically regulate water flow. They balance water conservation with flushing performance by ensuring only the exact amount of water needed enters the tank. If your toilet was installed before 1992, there’s a good chance it uses a ballcock instead of an EFV. Ballcock valves may be inexpensive and easy to install, but they’re no match for the efficiency of EFVs.
Toilet Water Usage: Environmental Impact
Water conservation might not be the first thing on your mind when you sit down to do your business, but your toilet’s water usage can have a big impact on the environment.
You aren’t just saving money on your water bill by choosing an efficient toilet model—you’re helping preserve natural water resources. If your wastewater flows into a sewer system, using less water means reducing the volume of water that ends up at water treatment plants, cutting municipal energy consumption.
For the environmentally conscious, selecting a gravity-assisted toilet model is a great way to reduce your footprint. By relying on the natural forces of gravity rather than air pressure, you can avoid the extra energy consumption and harmful greenhouse gas emissions associated with pressure-assisted toilets.
4 Ways to Conserve Toilet Water
Looking to maximize your toilet’s water efficiency? Here are 4 ways to ensure your toilet isn’t using more water than necessary.
Inspect and Replace the Flapper Valve
When you flush your toilet, the flapper valve lifts to allow water to leave the tank and enter the bowl. A misaligned or damaged flapper valve can allow water to continually escape, leading to an ever-running toilet. If your toilet sounds like it’s constantly refilling, your flapper valve may need attention. 
Not to worry—you can easily realign or replace a flapper valve by yourself. Check out our guide on replacing a toilet flapper the right way to get started.
Inspect Your Fill Valve
The fill valve connects the water supply line to your toilet tank. A poorly adjusted or damaged fill valve can cause too much or too little water to be pushed into your tank. Believe it or not, both issues can result in wasted water! Here’s how:
- Too much water enters the tank: If the water level in the tank rises too high, excess water will be siphoned out of the tank by the overflow tube. This leads to wasted water.
- Too little water enters the tank: When the tank doesn’t fill adequately, it won’t contain a sufficient volume of water to flow into and clear the bowl. This means you’ll need to flush several times, wasting more water.
Suspect a faulty fill valve if your toilet constantly runs or fails to flush effectively. If this sounds like your problem, we’ve got you covered. Check out our step-by-step guide on replacing a fill valve here.
Check for Leaks
Next time you’re cleaning your toilet, make a quick outer inspection to ensure you don’t have any sneaky leaks. Even tiny drops of water can add up to big water wastage, hurting your bank account and the environment.
Take a close look at the bowl, tank, and around the trapway, searching for any leaks. Don’t forget to check the base of the toilet. For a more thorough inspection, you can purchase toilet leak dye to place in your toilet water. This will help you detect any leaks that are invisible to the naked eye.
If you find a leak, your plan of action will depend on its location. Leaks near the tank or bowl may be caused by issues with the flapper, fill valve, or tank bolts. Leaks around the base of the toilet are often the result of a worn or improperly installed wax ring. Luckily, most of these causes have simple DIY solutions—read more here.
If you find a crack in your toilet’s porcelain, you may be in a bit of hot water. Though cracks can sometimes be temporarily sealed with waterproof epoxy, the toilet or affected part will likely need eventual replacement. Not to worry—we have a guide on how to install a toilet the right way.
Invest in an Eco-Friendly Toilet
If all else fails, consider upgrading to an eco-friendly toilet. The EPA federal standards cap maximum water usage at 1.6 gallons per flush, making newer toilets drastically more efficient than older models. If you really want the most bang for your buck, take it a step further and go with a WaterSense model, which, again, uses no more than 1.28 gallons of water per flush.
While you’re at it, consider a dual-flush toilet to save money and water. These models give you the option to use less water for smaller waste loads. Though specific usage depends on the model, it’s common for dual-flush toilets to use less than 1 gallon of water for smaller loads!
Bottom Line
Your toilet is likely one of the biggest contributors to your monthly water bill, especially if you have an older model. Many factors determine a toilet’s water usage, and you can optimize your toilet’s efficiency by making any necessary repairs.
The quickest way to ensure maximum efficiency, however, is by upgrading your toilet. Federal standards dictate modern toilets must use no more than 1.6 gallons of water per flush, saving you water and money. You can maximize the savings even more by investing in a WaterSense-certified toilet, which uses no more than 1.28 gallons per flush. If your old toilet has you swimming in worry about water usage, take a trip to your local plumbing supply store today to check out some new models. Your bank account and the environment will thank you!