How Waterless Urinals Work

A standard urinal uses water to flush the urine into a pipe known as a “P-trap.” The shape of this pipe, which is not unlike the ones installed under most sinks in restrooms and kitchens, creates a water seal that prevents sewer gases from escaping into the restroom.

“Plumbing code states you can have a certain amount of liquid between people in the bathroom and sewer gases,” Schneringer explains.

Unlike standard urinals, however, waterless urinal pipes are installed on a downward pitch to allow the urine to flow naturally to a central discharge pipe or into the main sewer line. If there are urine puddles in the urinal, then the pipe may be installed incorrectly. To prevent sewer gases and urine odors from entering the restroom, waterless urinals require a cartridge to be securely inserted into the urinal drain.

When urine flows into the cartridge, it acts as a funnel using gravity to pull the urine into the drain opening and into the facility’s plumbing system. The cartridge further contains a liquid sealant — a buoyant fluid that floats to the top of the cartridge as urine enters and overflows the contraption — that serves as a barrier between urine, sewer lines and the restroom. Ultimately, this sealant helps to prevent urine malodors.

The common “ammonia” smell that is often found in commercial restrooms is the result of a chemical reaction between urine and water. To make matters worse, the water that is left behind after flushing remains on the surface of the urinal, and becomes a breeding ground for germs and bacteria. With waterless urinals, the only fluid to hit the surface of the unit is urine — generally a sterile substance — which drains and evaporates from the surface leaving it dry shortly after use.

“The longevity of the sealant liquid depends on traffic of the facility. In an airport or mall the sealant would need to be changed on a more frequent basis,” Schneringer says. “If the sealant depletes or accidently gets flushed down the drain too fast, or if the sealant is not present, the sewer gas comes up through the pipes. This is what causes the unpleasant fragrance.”

According to manufacturers, cartridges need only to be changed out three to four times a year, or after roughly 1,500 uses. And since regular irrigation isn’t required for these urinals, there is no water “turbulence,” aka the plummage of water and microbes sent into the air following flushing.

These devices also hold urine sentiment — otherwise known as urinal scale, sludge or calcification — the buildup of which can be a main source of restroom piping issues leading to expensive sewer maintenance costs.