Interior Bathrooms Toilets

Low-Flow Toilets 101: Here’s Why a Toilet Upgrade is Worth the Upfront Expense

If you have pre-1980 fixtures in your bathroom, you're wasting about 7 gallons of water per flush. Today's water-efficient toilets use 1.6 gallons of water—or less—per flush. What are you waiting for?
low flow toilets


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The Environmental Protection Agency says that an estimated 4.8 billion gallons of water are flushed down the toilet every day. According to the American Water Works Association, the average household uses 20 to 28 gallons per day just to flush the toilet. The Energy Policy Act of 1992 took a step in reducing water waste by mandating that all new toilets produced for residential use conform to a 1.6-gallon-per-flush (gpf) standard, moving away from conventional 3.5-gpf to 5-gpf models.

To encourage homeowners to replace conventional high-flow toilets with low-flush models, some states and municipalities offer tax incentives, rebates, and vouchers.

San Diego’s Water Conservation Program, for example, offers vouchers for commercial and residential replacement of 3.5 gpf or higher toilets with water-conserving models. Residents can save as much as $165 by using a voucher when replacing an old water-hogging toilet with a water-conscious version. A $165 voucher used on a $250 water-efficient toilet can mean payback in as little as 2 years, depending on the region. A homeowner should check into local or state incentives for toilet replacement.


How Much You Can Save With Fewer Gallons Per Flush 

You can save a lot of money by switching to an eco-friendly toilet, but exactly how much depends on the age of the existing toilet. If you have a home built before 1980 and haven’t upgraded the bathrooms, your toilets may each be guzzling up a whopping 7 gallons per flush. That’s a bit more than four times the 1.6 gallons per flush that today’s low-flow toilets use, and a little more than five times the 1.28 gallons per flush of a high-efficiency toilet. In fact, if you have a home built between 1980 and 1994, your toilets probably still use 3.5 gallons per flush. According to the EPA, you can save an average of $110 per year by switching to a low-flow toilet.

Is a low-flow toilet right for your home?

Low-flow toilets save water, making them environmentally friendly while lowering your water bill, but upgrading your toilet is an investment. The cost to replace an old toilet with a low-flow model ranges from $224 to $531, according to HomeAdvisor.

Switching to more green toilets may also require you to change some of your bathroom habits or even alter your plumbing. Because a low-flow toilet uses less water, it’s more likely to clog than a conventional toilet, which means occupants of the house will need to cut back on toilet paper use.

If you live in an older home and want to upgrade your toilet to a low-flow version, you’ll need to check the existing plumbing first. Low-flow toilets rely on pressure and gravity to move waste, so the plumbing below the toilet must have a steep enough slope for the toilet to work properly. If it doesn’t, you’ll need to hire a plumber to redesign the drain, which is an additional investment.

What are ultra-low-flush toilets?

low flow toilets

The first low-flush toilets had trouble clearing the bowl and often required more than one flush, which defeats the purpose of a low-flush toilet. To counter these complaints, ultra-low-flush toilets (ULFTs) soon appeared on the market, with better flushing mechanisms and design improvements. Modified tanks, elongated bowls, and increased flushing velocity ensured improved performance with less water. “It was essentially a change in bowl shape, water flow, and trap design,” says Rob Zimmerman, Kohler’s senior staff engineer of water conservation initiatives.

Like conventional toilets, ULFTs come in gravity-fed and pressurized versions. Pressurized models have been criticized for excessive flushing noise, prompting industry manufacturers to take notice. “Our Highline Pressure Lite model is a pressurized toilet that uses 1.1 gallons per flush,” says Zimmerman. “Improvements in the hydraulic system have resulted in a quieter flush. It’s still louder than a gravity-fed toilet, but it doesn’t sound like an airplane taking off.”

RELATED: Buyer’s Guide: The Best Toilet Seats

Types of Low-Flow Toilets

The toilet industry’s leaders in water conservation are the high-efficiency toilets (HET) and dual-flush toilets. Most major manufacturers produce high-efficiency and dual-flush toilets, including The Home Depot’s in-house brand Glacier Bay and major manufacturers like American Standard and Kohler.

High-Efficiency Toilets

The industry defines a high-efficiency toilet as a toilet that uses 20 percent less than the 1.6-gpf low-flush or ultra-low-flush models, or 1.28 gallons of water per flush.

With the introduction of HETs, some municipal and community water-saving incentive programs have updated their offers. In San Diego, an HET replacement can be worth up to $165 per toilet, while a 1.6-gpf ULFT earns $75 per fixture. HETs are one of the highlighted categories under the EPA’s WaterSense program, which approves, promotes, and labels water-efficient products just as the Energy Star program certifies energy-efficient products.

Low-Flow Single-Flush Toilets

A low-flow single-flush toilet uses just 1.6 gallons per flush, which is less than half the 3.5 gallons that a normal-flow pre-1994 toilet uses. While they won’t save as much water as dual-flush or high-efficiency toilets will, low-flow toilets are the more affordable option.

RELATED: Buyer’s Guide: The Best Toto Toilets

Dual-Flush Toilets

As their name suggests, dual-flush toilets can flush in two different ways. These toilets have two buttons on the tank lid, one for solid waste that flushes at a rate of 1.6 gpf, and another for liquid waste that flushes at a lower rate of 0.8 gpf. While this design can save more water than a single-flush low-flow toilet, dual-flush toilets have a higher up-front cost and may be difficult for some people to operate.

Pressure-Assisted Toilets

A pressure-assisted toilet features a sealed tank that pressurizes the water inside it. When you flush, the water is expelled forcefully into the bowl, producing a powerful flush while using only about 1.2 gallons of water.

Single-Flush vs. Dual-Flush Toilets: What’s the Difference? 

ow flow toilets

Low-flow single-flush toilets are the most common toilets found in homes today. They use 1.6 gallons of water per flush and have a lever on the side of the tank that flushes the toilet.

Dual-flush toilets, in comparison, have two buttons on the top of the tank. One button flushes using 0.8 gallons of water and is meant for liquid waste; the other button flushes using 1.6 gallons of water for solid waste. While dual-flush toilets save more water than single-flush toilets, they cost more, are more complicated to service, and can be difficult for some people to operate.

You can purchase a kit that will allow you to convert a single-flush toilet into a dual-flush toilet. It’s important to note, however, that a conversion kit will not give an existing toilet the same benefits as a dual-flush toilet. While it will decrease water use for liquid waste to 0.8 gpf, the toilet must still use the entire tank—and hence its full water capacity—to flush solid waste.

RELATED: 12 Ways You’re Wasting Water at Home

Final Thoughts

Upgrading to a low-flow toilet is a great way to dramatically improve the efficiency of the toilets in your home, allowing you to save tens of thousands of gallons of water each year. While these savings may make such an upgrade seem to be a no-brainer, there are some factors you should consider first. There is, of course, the up-front cost of purchasing a new low-flow toilet. As well, these toilets lack the flushing power of conventional models, so you’ll need to be more mindful about the amount of toilet paper you use. Finally, if you live in an older home, you’ll need to check the design of the drain below the toilet to make sure it will work with a low-flow model.

FAQs About Low-Flow Toilets

If you’re wondering how much water low-flow toilets save or wondering if a dual-flush toilet might be right for your household, then read on for answers about these water-saving toilets.

Q. What is a low-flow toilet? 

A low-flow toilet is a toilet that uses 1.6 gallons of water or less per flush, which is less than half the 3.5 gallons of water that many older toilets use.

Q. How does a dual-flush toilet work? 

Dual-flush toilets have two buttons located on the top of the lid. One button flushes the toilet using just 0.8 gallons, which is suitable for liquid waste, while the other button uses 1.6 gallons to flush solid waste.

Q. Are dual-flush toilets worth it?

A dual-flush toilet will save more water than a low-flow toilet; however, dual flushes do cost more up front and some people may find the buttons less convenient to use than the flushing mechanism on a standard toilet.

Q. How much water does it take to flush a high-flow toilet? 

The amount of water a high-flow toilet uses depends on its age. Toilets manufactured between 1980 and 1994 can use as much as 3.5 gallons per flush. Toilets made before 1980 can use as much as 7 gallons per flush.

Q. Do low-flow toilets clog more easily than conventional toilets? 

While plumbing technology has evolved to improve the functioning of low-flow toilets, because they use less water than high-flow toilets, they are more susceptible to clogging.