Ballcock / Float Valve

The valve mechanism inside a toilet cistern that controls the refill of water after flushing. A plastic or metal float rises with the water level and shuts off the inlet valve when full. A faulty ballcock can cause continuous running (water constantly entering the overflow pipe), a slow fill, or a cistern that won't refill. Replacement ballcock valves are inexpensive and straightforward for a plumber to fit.