No.1 U.K. Professional Trade Forum, Plumbing, Gas, Electric, Tiling and Joinery Forum

Hi, hopefully some can help me with this frustrating problem.
My Cold water loft tank is overflowing intermittently and only stops when I draw hot water from taps, showers etc.
How is the back flow of water into the tank happening. Some things I have done so far..
New ball valve fitted and working.
Brand new hot water cylinder fitted by a plumber.
Help !!!
Peter

Do you have any mixer taps or a mixer shower with no double check valves? And the cold from mains supply?

oh no, not the 'you need a new cylinder' jobbie!