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January 18, 2018

Diaphragm or piston flushometer? Answer these 3 questions.

By Mike Gipson, Sloan Product Line Manager—Flushometers

Architects, engineers and installers of commercial restrooms have a choice to make with every new project: diaphragm or piston flushometer?

Since diaphragm flushometers account for 75% or more of all flushometers sold in the United States, it would be easy to just specify diaphragms for all your projects. But the best way to make this decision is by asking questions about the environment in which the flushometers will be placed.

Whether a flushometer uses a diaphragm or a piston to control the bypass between the upper and lower chamber may seem like a minor difference, but that difference can have a huge impact on a flushometer’s long-term performance. The right specification today can save a building owner significant maintenance and replacement costs over the years.

How do you match the right flushometer to your next project? Answer these three questions:

  1. What kind of traffic will the restroom experience?

In high-traffic environments such as airports and stadiums, diaphragm technology is the right choice. Its static sealing mechanism proves more durable than the sliding dynamic seal in pistons, which can deteriorate under conditions with heavy traffic.

Take O’Hare International Airport, where nearly 75 million passengers passed through in 2016. Sloan’s Royal 111 ESS TMO diaphragm flushometers (for wall-hung water closets) and Royal 186 ESS diaphragm flushometers (for standard high-efficiency urinals) accommodate hundreds of thousands of people each day.

In low-traffic situations, both diaphragm and piston technologies offer water-saving solutions with similar lifespans.

  1. What will the water quality be?

Poor water quality often compromises the performance and reliability of your flushometers. Water containing excess solid particulate matter or dissolved salts acts like an abrasive on flushometer seals, and their deterioration can cause leaks and short flushes.

When a restroom’s water quality may be questionable, diaphragm flushometers are the better choice. Diaphragms hold up better in water conditions with a high level of chloramines, thanks to their thick diaphragm sections, while the sliding dynamic lip seals in piston flushometers are more likely to deteriorate.

This advantage is why the Chicago Journeymen Plumbers’ and Technical Engineers Training Center installed Sloan’s Reclaimed Water diaphragm flushometers to handle the facility’s reclaimed and treated rainwater. The Reclaimed Water flushometer, with its characteristic purple components and handle, is built with synthetic rubber and semi-red brass to withstand the higher contaminant levels of reclaimed water.

Diaphragm valves tend to be more accommodating than pistons, and they can better handle changes and fluctuations in a water supply system.

  1. What will the operating conditions be?

Harsh operating environments can cause a flushometer to malfunction or operate at low efficiency, wasting water. In low-pressure (20 psi or below) and weak system situations, piston flushometers provide slight performance benefits versus diaphragm flushometers.

For instance, many high-rise buildings in international markets situate the water tank on the roof, leading to low water pressure on lower floors. Other communities may have low pressure, as well. Newport News Public Schools, for instance, installed 1,400 new Sloan GEM 111 piston flushometers throughout the school system because of lower water pressure conditions.

On the other hand, diaphragm flushometers are the better choice in high-pressure situations where a system could experience very high static pressure conditions but not recover quickly after a flushometer cycle.

Engineered for water conservation

Despite the relative strengths of diaphragm and piston flushometers, each technology is engineered to meet water conservation goals. With high-efficiency toilets producing an average flush volume of 1.28 gpf and high-efficiency urinals using 0.5 gpf or less, both piston and diaphragm technologies provide significant water savings per flush compared to more traditional flushometers.

Sloan, by the way, pioneered water conservation technology with the invention of the diaphragm flushometer in 1906, then developed piston technology 20 years later. For your next project, consider all the above factors when choosing whether to specify diaphragm or piston flushometers, but rest assured that any Sloan flushometer you select will be the sustainable choice.

Mike Gipson is Sloan’s Product Line Manager—Flushometers. His background includes extensive new product development for a wide range of commercial industries. Want to know more? Talk to Sloan!

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