Can anyone please tell if it's possible for the header tank water level to rise when no water is entering through the Ball Valve flow or the expansion pipe?
When the Washing Machine is used the water level rises to a point above the overflow level, I can only assume that back pressure is causing water to enter the tank through one of the two cold water supply pipe at the base of the tank.
Firstly, is this possible? And secondly, how can I fix it?
Any help would be gratefully received