Diaphragm vs. Piston Flush Type Toilets: Which Is Best?

Aug 26, 2023

Before diving into the basics of the diaphragm and piston flush type toilets and which is best for your needs, it's important to note that there is no definitive top choice. In fact, both styles of lavatories are effective in their own right.

As such, it's essential that you determine what characteristics and capabilities you need from a toilet before deciding on the specific flush configuration. Read on to learn the differences between these types of toilets and which one is ideal for your commercial restroom.

This style of flush toilet features a waterless tank that controls toilet valve pressure with a disc-like object known as a diaphragm. A select amount of supply water rests in a control chamber located above the diaphragm. This water supply provides pressure to the diaphragm and creates a tight seal. During the flushing process, the relief valve is activated, releasing the diaphragm and allowing pressure to build throughout both chambers. Ultimately, the pressure imbalance creates a steady stream of water through the main barrel using a highly-effective shut-off mechanism.

Due to the efficiency of the diaphragm assembly, this technology is ideal for water closets in high-traffic public areas. Local stadiums, airports, and other big commercial buildings benefit from the speed and effectiveness of diaphragm flush type setups. Diaphragm assemblies are also perfect for high-pressure systems or plumbing infrastructure with volatile backflow or back-pressure conditions.

Piston assemblies function similarly to diaphragm flush type toilets in that they both feature multiple control chambers that utilize pressure to activate the flushing mechanism. However, instead of a diaphragm component, these models boast pistons. These hollow pistons often house sections of the rubber lip seal and the system's bypass hole, with the relief valve separating the control chambers. When flushed, water tilts the relief valve and triggers the piston, which releases properly pressurized supply water to the main barrel.

Piston flush type toilets are less efficient in high-traffic applications. Instead, this technology is ideal for systems with clean water conditions and lower pressure levels. The piston design compensates for low system pressure and can effectively handle commercial use. Piston flush type toilets also use slightly less water per flush compared to the more aggressive diaphragm configurations.

So, which of these toilets is best for your commercial restroom? If you manage a smaller building with only a few water closets per bathroom, piston assemblies are completely suitable. They’re also preferred for low-pressure plumbing systems. However, diaphragm flush type toilets are also (mostly) functional in these applications, as well as in higher-traffic environments. As such, this technology is often the most practical option for businesses. If you opt for a diaphragm assembly, the most popular options are either the Sloan Royal or Regal flushometers.

There are many factors that may make both diaphragm and piston flush type toilets best for your commercial restroom needs. Consider contacting a professional plumbing business for advice and assistance in finding the ideal product for your existing plumbing infrastructure.