When an overflow pipe is dripping or running with water, one of the most common causes is a problem with a float valve. ... If the float valve doesn't operate properly, the cold-water feed may not fully switch off, causing the water level to continue to rise above the overflow.

Is a leaking overflow pipe an emergency?

Small, dripping leaks may not require this, but if there's a lot of water leaking from the overflow pipe, the situation could be more of an emergency. Only contact a Gas Safe registered engineer to fix boiler issues that you don't know how to handle.

Why is my overflow pipe flowing?

When an overflow pipe is dripping or running with water, one of the most common causes is a problem with a float valve. Float valves are found in toilet cisterns, cold water tanks and central heating feed and expansion tanks. ... When the water in the tank is used, its level goes down and so does the ball and arm.