About this service
A running cistern is often a flush valve or inlet valve fault. Say whether the water runs into the bowl or the overflow, and how long it has been doing so.
Use this page when the toilet still flushes but the cistern will not stop, the flush is weak, or the button does not stay down. A bowl that fills and will not empty is a choke, not a flush repair.
You do not need to open the cistern before you enquire. If you already looked inside, describe what you saw and leave the lid as you found it.