Look where the overflowing pipe comes out of your house.
Overflow pipe dripping from roof.
If the leaking overflow pipe is at loft level or protrudes from the eaves of the roof then the source is either the cold water storage cistern or the smaller feed and expansion cistern that supplies the boiler if you have one.
However if it s at loft level and protrudes from the eaves of the roof then it could be coming from your cold water or central heating feed and expansion tank.
How to diagnose and repair a dripping overflow.
Is it from the eaves of the roof near a bathroom toilet or near a boiler hot water cylinder.
It s designed to release the pressure when there is too much of a load built up inside the water heater.
2 look at the type of pipe the water is coming from what is the material is it metal of plastic.
For any roofing issues visit.
In all cases if you do not know which is the problem cistern then a visual inspection will tell you.
So this release of its pressure causes your hot water tank overflow pipe dripping towards the floor where the hot water heater is placed.
This could be either the cold water storage cistern which supplies the hot water cylinder and possibly the cold bathroom taps.
Or it could be the smaller feed and expansion cistern which puts water into the central heating circuit.