Dry urinal

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Waterless urinals in a fast food restaurant

A dry urinal (also known as waterless urinal ) is a urinal with a drain, but without flushing water .

Conventional urinals require at least three liters of water per flush, whereas waterless urinals work without any water or flushing device.

The first dry urinal as it is today was developed by Wilhelm Beetz at the end of the 19th century after inventing what he called the oil siphon. He called the sealing liquid that he also developed as urinol .


Dry urinals are operated with a siphon into which a biodegradable "barrier liquid" is filled. This liquid is lighter than urine and hydrophobic . The heavier urine can thus flow through the barrier liquid without mixing with it. In contrast to the conventional urinal, in which the odor trap is made by the flushing water remaining in the siphon, in the dry urinal the escape of bad smells is prevented by the sealing liquid floating above and thus no water is used. Another form of dry urinals works with a liquid- permeable membrane .

Both forms must be maintained (refill barrier layer or replace membrane). In addition, if a membrane is used, it must be ensured that no foreign objects can be thrown into the urinal (e.g. cigarette butts). This system is also offered in combination with a flushing nozzle, which should make do with one liter of water per flush.

A third system works with a float in a liquid-filled container. It is pressed down by the impinging liquid so that it can flow off, then it presses up again against the drain so that no sewer gases can escape. Maintenance costs can occur here due to leaks in the float drain connection (if necessary, replacement or cleaning of the parts).


Of the approximately six million urinals in Germany, around 5000 were waterless in 2006 (450 of them had been since the Expo 2000 in Hanover) and around 100,000 in 2009.

Web links

Commons : Dry urinal  - collection of images, videos and audio files

Individual evidence

  1. a b Eco-Innovations: Waterless urinals. No water consumption and more hygiene. (PDF, 170 kB) Wuppertal Institute for Climate, Environment and Energy , September 2009, accessed on April 30, 2015 .