As illustrated by this graphic, there are four basic stages in the functioning of a waterless urinal.
- Urine enters the bowl and, rather than being flushed away (with each flush using up to a gallon of purified water), it drains naturally through small holes in a waterless urinal cartridge located at the bottom of the urinal bowl.
- Gravity draws the urine through a special oil-based liquid (often blue in color). Because the urine, being mostly water, is denser than oil, it passes through the oily layer, which naturally re-forms into a seal almost immediately. Although the oil trap allows heavier liquids to pass through, it does not allow odor-causing and sometimes dangerous sewer gasses to pass back through, but instead traps them underneath.
- A barrier inside the waterless urinal cartridge breaks the flow of the liquid to prevent excessive turbulence, driving the oily sealant out of the cartridge.
- Urine moves slowly below the barrier and into an exit chamber. When the fluid level in the exit chamber exceeds the height of the drain, it spills over naturally into the sewer pipe and is drawn away by gravity.
The popularity of waterless urinals is increasing all the time, and this is driving up the demand for replacement cartridges. Some of these replacement waterless urinal cartridges are made by established urinal manufacturers and other, often more budget-friendly replacement compatible cartridges are also available.
With a wide variety of pricing options, it is a good idea for building owners and custodial staff to carefully consider which cartridge they use. Some common brands to investigate include Sloan, Kohler, Falcon, Hybrid H20 and Smarty Bee.