Toilet Constantly Running – Water Trickling into the Bowl

The most common cause is a worn rubber valve (flush valve) inside the cistern that is no longer sealing properly. Remove the cistern lid and check whether the float valve is correctly positioned and whether the rubber seal on the bottom valve has hardened or deformed. In many cases, simply replacing the rubber seal – available from a DIY store for a few pounds – is sufficient. Turn off the water supply first using the isolator valve (the small valve beneath the cistern). If the water continues to run or the isolator valve cannot be turned, contact a plumber.