Roger shows you how to replace an old broken fill valve with a Fluidmaster Bottom Entry Fill Valve. Fix your toilet flush now. The 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 most popular valve in the world. Replace your old style ballcock valve with a better performing Fluidmaster