This
is a regular question asked of us and we usually have to answer by asking
several questions.
Once you understand the function of the washers and valves it becomes
easy to locate the problem. Bring in the offending washer or valve to
ensure we provide you with the correct replacement.
While many brands and styles of cisterns exist, all have the following
parts although they may look a little different.

Inlet Valve: Lets the water
into the cistern.
Float (ball): Controls the
level of water in the cistern
Inlet Washer: Shuts off the
water as the float rises with the water level.
Outlet Valve: Flushes the pan
when the button is pressed.
Outlet Suction Washer: seals
the water in the cistern until flushing required.
Overflow Tube (not in some cisterns):
Drains off excess water into pan should inlet washer fail.
Flush Button: Mechanism to
flush pan.