One of the most common toilet repairs is adjusting or replacing the fixture s fill valve.
Roof tank ballcock.
There should be no water gushing out.
Make sure the water is turned off by taking off the lid of the cistern or tank and pushing down on the ballcock arm.
How to change the ball valve ballcock in your cold water storage tank in the loft.
On a roof tank you should find the tap on the top pipe.
Ballcocks also known as float valves are found in water tanks and are used to control the flow of water into the tank.
Just follow this video it s easy save money on expensive plumbers.
They work by rising with the water level in the tank which in turn activates a lever which then shuts the valve.