What is a fill valve? Well its that all important device that fills your toilet cistern back up after flushing the loo. Providing water
Firstly there are two different types. The old style are the ones are usually brass with an arm and plastic float. The modern fill valves have a float that slides up and down its body (which can be adjusted in height depending on the volume of water) and are much more being accurate.
Next, how do they work? When you flush the toilet the cistern empties, the float on the fill valve will drop and allows the arm to release the washer within the valve to let the water in to fill up the cistern to its previous level.
As the cistern fills up the float will be pushed up by the water and will shut off the water coming in by pressing the rubber diaphragm washer, then hey presto the cistern is full and your toilet is ready for flushing again!
But like everything over time these washers gradually start to fail and need replacing and as always there are different types for different valves
You can find diaphragm washers here. Or if you fancy a new start our range of fill valves can be found here
Modern Fill Valve Old style Fill Valve