The unit has no moving parts to jam or freeze, no mains electricity, pumps or generators and requires no mains water supply. The equipment consists of twin entry ramps, a 12.2m long bath filled with water and twin exit ramps.In the bath, some 150 mm below water level, a shaped, horizontal grip is designed to vibrate the wheels as the vehicle drives through without stopping. This grid is claimed to break up mud on the tyres, while the forward motion of the vehicle causes water turbulence which washes off tyre treads and walls.Muck falls to the bottom of the bath, below the grid, where it can be cleaned out by on-site plant, usually at weekly intervals.The water bath requires no special lay-by facilities and no human input other than the vehicle's driver is necessary during use. The water level is topped up by gravity feed from an 11,360 litre header tank via a ball cock. The company says that typical water usage is some 9,100 litres a week.Where contractors do not want to get involved with capital outlay, Wheel Wash will hire the equipment on a weekly basis. When required, vehicle counting systems can be added to the equipment.