Consider Dual-Flush, High-Efficiency Toilet Options

Advantages include less water use, longer bowl rinsing, drainline washdown and carry.
Consider Dual-Flush, High-Efficiency Toilet Options
Ed Del Grande

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When recommending a toilet choice, plumbers should look into dual-flush toilets along with single-flush toilet systems to help best fit customer needs.

As far back as I can remember, dual-flush toilets have been the original water-saving toilets. This was decades before new flushing technology enabled single-flush high-efficiency toilets, or HETs, to powerfully flush with less than 1.6 gallons of water.

The concept of a dual-flush toilet was simple and could be carried across the board no matter the maximum water use requirement at the time. One flush actuator used the full capacity of available water in the toilet tank, a second actuator partially flushed the available water in the tank.

Many years ago, when I first worked with dual-flush systems, most toilets were using over 2 gallons per flush. So, if you could save about a gallon of water on selected flushes, the water-saving potential was huge. Today, with the very stingy single-flush HETs on the market, dual-flush systems may not have as much of a water-saving impact as they once had. But, they do offer some convenient flushing features and should not be overlooked when choosing a toilet.

To qualify for high-efficiency toilet status, a toilet needs to perform up to industry testing and use less than 1.3 gallons per flush or gpf. Dual-flush toilets can qualify for HET status because in most areas the maximum limit on a full flush is set at 1.6 gpf.

With the partial-flush setting option figured into the equation for most flushes, this usually means that a dual-flush toilet nets out to meet the HET limits. A big question I have been hearing lately is, "If single-flush and dual-flush toilets are now flushing with just about the same amount of water overall, why go with a dual-flush toilet?"

My reply is that while both systems save water and flush with power, in some instances the dual-flush system may provide some flushing advantages. So, keep these dual-flush features in mind if you’re looking to offer a few extras to customers:

Longer bowl rinsing when using the full-flush setting.

  • With most single-flush HETs, the bowl-rinsing cycle is quick since every flush is using 1.3 gpf or less. With the dual-flush, full-flushing setting for solids, the extra water allowed for the flush can provide a little extra bowl rinsing.

Drainline washdown and carry.

  • Along the same lines of having a little extra water for bowl rinsing, a dual-flush HET in full-flush mode can deliver more water for drainline carry when flushing solids. This may be helpful for older drainline systems.

Less water use on the partial-flush setting than most single-flush systems.

  • In most instances, toilets are only flushing liquids and very light loads of toilet paper. With the partial-flush setting on a dual-flush toilet, only about a gallon of water may be used per flush. For light-duty areas like a small powder room, this super-saving water feature may be used more often.

Now that you know some flushing advantages with dual-flush HETs, you should also know that you are not limited to only one type of dual-flush system. Here are four popular dual-flush systems you may want to choose from:

Top split-button actuator.

  • This is the most popular type of dual-flushing mechanism I have worked with. Mounted on top of the toilet tank, the split-button system is easy to access and service. One side of the split-button delivers a full flush and the other side of the button provides the partial flush. Because the buttons are located up high on the tank, this actuator can be very easy for the user to operate and understand.

Wall-mount actuator plates.

  • This large, recessed dual-flush actuator is usually used with wall-mount toilets that have in-wall toilet tank systems. Since the wall actuators are large, flat and side-by-side, it’s also a good choice for special-need applications. The framed plates can be removed for access to the in-wall toilet tank. Decorative finishes are available for the plates as well.

Electronic smart-flush actuators.

  • This type of actuator is found in smart toilets and/or toilets that use electric pump motors in place of gravity-flush systems. Electronic buttons activate the flush pump for longer or shorter durations depending on if the user wants a full flush or a partial flush. This system can also work with remote-control units for smart toilets.

Nested trip-lever actuators.

  • This innovative dual-flushing actuator looks and operates like a standard side-mounted toilet tank lever, but the cable-driven handle actually has two nested levers that look like one handle. You can depress the main part of the handle for a full flush, or depress the tip of the handle to activate the partial-flush lever. The tip of the handle is often green to alert users of the water-saving option.

In the future, toilet water use regulations may be even lower and we can even reach a point when single-flush toilet systems may be the only option. But for now it still makes sense to consider dual-flush toilets for selected installations.

For a companion video to this article, please visit my website at or click on the video below.

About the Author: Ed Del Grande is a three-time master plumber, GBCI LEED green associate and contractor with licenses in pipe fitting, fire protection and plumbing. He grew up in a family-owned plumbing business, and has 30-plus years of construction experience.

A self-employed contractor and professional comedian, he combined his performing and construction talents to became a pioneer in home-improvement television. Starting on HGTV with shows such as Dream Builders and The Fix, Del Grande helped build the DIY Network and with shows such as Warehouse Warriors and Ed The Plumber


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