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How waterless urinals work

Four parts make a waterless urinal work in a commercial washroom: gravity drainage, an odour trap, a care system and a servicing plan. Leave any one out and problems follow.

1

Gravity drainage

A flushing urinal uses water to carry urine to the drain. A waterless urinal doesn't need to.

The bowl's shape directs urine to the outlet, and gravity takes it from there into the drain line. The fixture has no water supply and no flush valve, so nothing is used or discharged except the urine itself.

Because there is no flush water to dilute it, the condition and slope of the drain matter. Drains that slope the wrong way or are lined with old deposits need attention before a waterless fixture is installed.

Flushing urinal compared with a waterless urinalLeft: a conventional urinal is fed by a water supply pipe and flush valve, and each flush sends clean water through a water-filled trap to the drain. Right: a waterless urinal has no supply pipe or flush valve; urine drains by gravity through a sealed odour trap cartridge to the same drain.Flushing urinalWater supplyFlush valveWater-filled trapDrainClean water is used on every flush.Waterless urinalNo supply pipe or flush valveOdour trap cartridgesealed when not in useDrainGravity drainage; no flushing water.
Simplified illustration, not to scale. Actual fixtures, trap designs and drain connections vary by manufacturer and site.

2

The odour trap

Every urinal needs a barrier between the washroom and the sewer. In a flushing urinal it is a water seal. In a waterless urinal it is a trap cartridge.

Designs differ between manufacturers. Some use a layer of sealing liquid that urine passes through. URIMAT's MB-ActiveTrap uses a vertical membrane: liquid pushes it open, and when the flow stops it closes, sealing off drain air.

The trap is a consumable. It is replaced as a complete cartridge when its indicator shows it is spent.

How a membrane odour trap worksTwo states of a simplified trap cartridge. In use: liquid flows down past a cleaning block and opens a vertical membrane before leaving to the drain. At rest: the membrane closes and seals the drain from the washroom. A coloured surface under a clear cover becomes visible when the cleaning block has dissolved and the cartridge needs replacing.In useFlow opens the membraneand drains by gravity.At restThe membrane closes andseals off drain air.Clear cover withlife indicatorCleaning blockVertical membrane
Simplified illustration based on the manufacturer's published description of its MB-ActiveTrap (membrane, integrated MB-ActiveCube cleaning block, and indicator). Not to scale, and not an engineering drawing.

3

Microbiological care

Without flush water, residues have to be managed by the care system instead. URIMAT's approach uses biological products:

  • In the trapThe MB-ActiveCube, a cleaning block above the membrane, dissolves gradually to reduce deposits and encrustation in the trap and the drain line. Its cover setting controls how quickly it dissolves.
  • On the bowlMB-ActiveCleaner, a pH-neutral cleaner containing bacterial spores, is diluted with water and used in routine cleaning to break down organic residues that cause odour.
  • What it isn'tThese products are cleaners, not disinfectants. Follow the supplier's instructions and safety data for each product.

4

Planned servicing

A waterless washroom works when servicing is scheduled, not left until someone complains.

  • Every cleaning roundClean the bowl and the area around it with the specified cleaner.
  • RegularlyCheck each trap's indicator. URIMAT gives an average trap life of 7,000 to 8,000 uses.
  • When dueReplace the trap cartridge following the manufacturer's procedure. Ceramic URIMAT models have a valve that closes the drain during the change.
  • PeriodicallyCheck and rinse the drain line, because urine sludge can collect over time without flush water.

Most odour complaints in waterless washrooms trace back to a missed step here, or to floors, walls and floor drains rather than the urinal. The manufacturer itself names maintenance failure as the most important cause.

Plan it properly from the start

A facility assessment covers drains, servicing and costs as well as savings, so the system works the way it should.

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