The toilet fill valve fills the toilet tank with water from the water supply line after it has been emptied by a flush. It replaces the ballcock and is more efficient and easy to install. This is an anti-siphon design-fill valve with adjustable height from 9" to 14". The 400A Toilet Fill Valve is the most popular fill valve in the world and the quietest fill valve on the market. Replace your old style ballcock valve with this better performing Fluidmaster toilet fill valve.