How Much Water Do You Need To Flush?

As plumbing products continue to become more water-efficient, including 1.0 gallon-per-flush water closets and urinals utilizing only one pint of water to flush, there's greater interest in low-consumption fixtures. The American Society of Mechanical Engineers (ASME) is expected to soon bring more clarity to some of these low-consumption flushing terms by defining them in applicable standards.

John Watson, director of technical services for plumbing manufacturer Sloan Valve Company and a member of the ASME A112.19.2 Working Group, says that no "official" definition has yet emerged in an approved consensus standard for High-Efficiency Urinals (HEU) and High-Efficiency Toilets (HET).

ASME will, however, likely provide those definitions when it next updates the ASME A.112.19.2 standard. For now, HEUs and HETs can be defined as follows:

An HEU is a urinal that performs to the current ASME A.112.19.2 performance standards while using no more than 0.5 gpf/1.9 Lpf to flush. This is a reduction from the current standard of 1.0 gpf/3.8 Lpf as required by the Energy Policy Act of 1992. By this definition, waterfree urinals are categorized as HEUs.

An HET is a water closet that meets the current performance requirements outlined in ASME A.112.19.2 but does so by either flushing at a maximum of 1.28 gpf/4.8 Lpf or by deploying a dual-flush device, which based on a typical 2:1 liquid/solid use ratio, averages a total flush volume of 1.28 gpf while achieving a MaP test score of removing at least 350 grams of waste.

"Dual-flush Flushometers are rising in popularity," says Watson, "partly because they easily meet HET performance standards."

In smaller buildings, Watson explains, it may be more advantageous to install manual dual-flush Flushometers in restrooms, because they have a regular set of users. "These users are more familiar with and conscientious about the facility, which means they are more likely to learn how to manually operate a dual-flush Flushometer to its full potential," he says.

But restrooms frequented by newcomers can certainly benefit from manual dual-flush Flushometers as well. Sloan includes signage with its UPPERCUT® dual-flush Flushometers, which can be affixed near the flush valve to quickly educate users on its usage and benefits. Proper operation by even a fraction of the users can equate to significant water savings.

Plus, as dual-flush flush valves become more common, restroom users will just intuitively know how to operate them—much in the same way they learned to adapt to sensor-operated Flushometers when they first emerged on the market.

Large commercial or institutional buildings with a transient population or restrooms in high-traffic areas such as airports, entertainment venues, and shopping malls may gain greater efficiencies from automatic operation. "For these restrooms, it makes sense to install the new electronic dual-flush Flushometers, which automatically initiate the appropriate flush cycle, depending on the amount of time the user remains in the sensor range," says Watson.