Waterless Urinals — How They Work and Where They Fit

How the seal works without water

Urine drains through the bowl into a cartridge at the outlet. Inside that cartridge sits a layer of sealant liquid — an oil, lighter than urine and immiscible with it. Liquid passing through sinks straight down through the sealant and away into the drain; the sealant floats back into place and closes over the top.

That floating layer is the odour barrier, doing exactly the job the water in a conventional trap does. Because nothing evaporates the way a water seal does, a waterless urinal actually holds its seal better in an infrequently used washroom, where a water trap can dry out entirely and let drain gas into the room.

The maintenance model is different rather than lighter. There is no flush valve to service, but the cartridge is consumable: the sealant depletes with use and has to be topped up or the cartridge replaced, typically after a few thousand uses. Skip it and the odour barrier is gone.

Where waterless makes sense — and where it does not

• Works well: water-scarce regions — Saving 15,000 to 45,000 litres per urinal per year is material where water is expensive or rationed.
• Works well: high-traffic commercial washrooms — Airports, stadiums and malls, where both the water saving and the absence of flush valves to maintain add up.
• Works well: infrequently used facilities — The sealant does not evaporate, so a seasonal or rarely used washroom does not develop the dried-trap odour a water-sealed urinal would.
• Works poorly: without a maintenance regime — The cartridge is consumable. A building that will not schedule replacement should not specify waterless.
• Works poorly: on old, shallow-fall drainage — With no flush volume, drain lines rely entirely on gradient. Marginal falls can accumulate deposits.
• Check local codes — Some plumbing codes still require a water supply to be roughed in to every urinal position even where none is used.

Frequently asked questions