Editing Urinal (section)

===Automatic flush===
[[File:Zurn OmniFlo urinal at Sheetz in Bedford PA.jpg|thumb|Urinal with automatic flush valve]]
[[File:Surveilluminescent Lights in Motion handwash faucets 02.jpg|thumb|Long-exposure photography shows the sensors' detecting range]]
Automatic flush valves solve the problems of previous approaches, and are common in new installations all around the world. A passive infrared sensor identifies when the urinal has been used, by detecting when someone has stood in front of it and moved away, and then activates the flush. There usually is also a small override button, to allow optional manual flushing when the sensor is not working.

Automatic flush facilities can be retrofitted to existing systems. The handle-operated valves of a manual system can be replaced with a suitably designed self-contained electronic valve, often battery-powered to avoid the need to add cables. Older timed-flush installations may add a device that regulates the water flow to the cistern according to the overall activity detected in the room. This does not provide true per-fixture automatic flushing, but is simple and cheap to add because only one device is required for the whole system.

To prevent false-triggering of the automatic flush, most infrared detectors require that a presence be detected for at least ten seconds, such as when a person is standing in front of it. This prevents a whole line of automatic flush units from triggering in succession if someone just walks past them. The automatic flush mechanism also typically waits for the presence to go out of sensor range before flushing. This reduces water usage, compared to a sensor that would trigger a continuous flushing action the whole time that a presence is detected.