Level Control Valves

Are used to manage the filling of tanks and vessels by means of a mechanical float that operates a small pilot valve to control the main valve. The main valve allows the liquid (often water) to flow down and impulse line to the pilot valve at the float. When the tank is full and the float is level, the pilot valve is closed and this prevents the main valve from opening. As soon as the level drops and the pilot valve opens, the main valve also opens and a small quantity of the liquid from the pilot line releases into the tank to maintain the open position of the main valve until the float is again level and both the pilot and main valves shut.

This is similar in principle to the altitude control valve more often used for supplying water to elevated tanks and reservoirs. With the altitude control valve, a float isn't used and instead a sensitive diaphragm responds to changes in pressure to determine whether the main valve should open or not.

Float level control valves are most often used for water or diesel storage tanks but can be used for other liquids where material compatibility is not an issue.