Single Flush vs Dual Flush Toilets: Which Is Better?

The quick answer

Dual flush toilets generally save more water per flush than single flush models because they let you choose a smaller flush volume for liquid waste. If you use the reduced flush mode for most flushes, a dual flush toilet can cut water use significantly over time. Single flush toilets use the same volume for every flush and are simpler in design. Both types can earn the Environmental Protection Agency's WaterSense label, which guarantees they meet strict efficiency and performance criteria.

How each type works

A single flush toilet has one flush volume, typically 1.28 or 1.6 gallons per flush. Every press of the handle releases the same amount of water to clear the bowl. A dual flush toilet has two flush options: a reduced flush for liquid waste and a full flush for solid waste. The EPA notes that a dual flush toilet can save even more water if you choose the reduced flush mode for liquid waste. The reduced flush uses a smaller volume of water, which can add up to substantial savings across a household.

Water usage and savings

Toilets are the main source of indoor water use, accounting for nearly 30 percent of a home's water consumption. Older, inefficient toilets can use as much as 6 gallons per flush. Modern WaterSense labeled toilets, which include many single and dual flush models, use 1.28 gallons per flush or less, which is 20 percent less than the federal standard of 1.6 gallons per flush.

If you replace old, inefficient toilets with WaterSense labeled models, the average family can reduce water used for toilets by 20 to 60 percent, saving nearly 13,000 gallons per year. Dual flush models add another layer of savings: by using the reduced flush mode for liquid waste, you avoid sending a full 1.28 gallons down the drain every time. Over a year, that difference can be significant, especially in households with multiple people.

Performance and certification

The EPA's WaterSense program requires all labeled tank-type toilets, whether single or dual flush, to meet the same rigorous performance criteria. These include mixed testing media flushability, bowl surface cleaning, drainline waste transport, and waste extraction. The performance criteria have been adopted into the national plumbing standard, ASME A112.19.2/CSA B45.1, so you can trust that a WaterSense labeled toilet will handle waste effectively.

The former low-flow toilets of the 1990s sometimes had performance issues, but manufacturers have redesigned their products to achieve both efficiency and performance. Today's WaterSense labeled toilets far outperform traditional toilets from the 1980s and 1990s. When comparing single and dual flush models, look for the WaterSense label to ensure you're getting a toilet that meets the same performance bar regardless of the flush mechanism.

Maintenance and usability

Single flush toilets have a simpler design with one flush valve, which can make maintenance straightforward. Dual flush toilets have an additional valve or mechanism for the reduced flush, which means one more component that could need attention. However, many modern dual flush toilets use tower or dual-flush valves that are reliable and easy to replace.

From a usability standpoint, dual flush toilets require the user to choose the appropriate flush level. If you prefer a no-fuss operation, a single flush toilet might be easier. But many people quickly get used to the two-button or two-lever controls. The EPA points out that dual flush toilets can save more water if you use the reduced flush mode, so the choice depends on your household's habits.

Making your choice

The best toilet for you depends on your priorities. If you want the lowest possible water consumption and don't mind learning the two-flush system, a dual flush toilet is a strong choice. If you prefer a simple, consistent flush and don't want to think about choosing a button, a single flush toilet may be more comfortable.

Also consider the flush volume. A 1.28 gallons per flush toilet is the WaterSense standard and works well for most households. If you're replacing an older 1.6 GPF model, you might not need the reduced flush savings, but a 1.5 to 1.6 gallons per flush toilet still meets federal standards and can offer a stronger flush. For a deeper dive into how dual flush mechanisms work, see our article on how dual flush toilets work.

Before buying, measure your rough-in to ensure the toilet fits your bathroom. Most residential toilets use a 12-inch rough-in, but you can confirm with our rough-in measurement guide. If you're concerned about WaterSense certification, check our WaterSense certification guide to understand what the label means.

What to pick for your use

Questions

Are dual flush toilets more water efficient than single flush?

Yes, dual flush toilets can save more water because they offer a reduced flush for liquid waste that uses less water than a full flush. If you use the reduced flush for most flushes, a dual flush toilet will use less water overall than a single flush toilet with the same full flush volume.

Do dual flush toilets perform as well as single flush?

Both single and dual flush toilets can earn the WaterSense label, which means they meet the same performance criteria for waste removal, bowl cleaning, and drainline transport. As long as you choose a WaterSense labeled model, you can expect comparable performance from either type.

Which flush volume is best for a bathroom?

The EPA recommends WaterSense labeled toilets that use 1.28 gallons per flush or less. This volume meets efficiency standards while providing good performance. For dual flush toilets, the reduced flush volume is often around 0.8 to 1.1 gallons, which adds to water savings.

Do dual flush toilets require more maintenance?

Dual flush toilets have an extra valve or mechanism for the reduced flush, which adds a component that could require maintenance. However, modern designs use durable valves, and many are easy to replace. Single flush toilets have a simpler mechanism, so they may be slightly easier to service.

Can I convert a single flush toilet to a dual flush?

Some conversion kits exist, but they are not always compatible with existing toilets, and the performance may not match a purpose-built dual flush toilet. If water savings are important, it's often more reliable to install a new dual flush toilet that is designed and certified for that purpose.