The sprinkler, operated by an infrared sensor, would be switched on between dusk and dawn. Chris Warren, partner of Icewit Design which came up with the blueprint, said: "There was a problem with human faeces and drugs. It is a pretty simple concept - a perforated copper pipe fixed to one of the walls and linked to the mains water, which would give someone a 10-second squirt. We are not sure whether it will prove workable - people may simply use it as a free shower. But it is really to protect private property. I wouldn't want to see them installed in doorways of shops."