DIY Doctor UK DIY Forums

My header tank is overflowing. The ballcock is new and is working OK. The excess water must therefore be coming from the vent pipe from the storage tank. What causes water to back up the vent pipe - is it hot water temperature too high? Or can there be another reason?

I have recently had a bathroom converted to a shower room. This required some extensive new plumbing. Could something have been done at that time to cause this problem?

Any help would be greatly appreciated!

hi bobby if you are absolutely sure the ballvalve is not leaking check the cold water storage tank [the large tank]if the water level is higher than the expansion tank [small tank] suspect the coil in h/water cylinder is leaking [new cylinder]. there are many reasons for water to back up the expansion pipe but you didn't say if it did, hope this helps john

if you've recently had a dodgy mixer shower installed high pressure cold water can be forced through hot side, back into cylinder and back to tank. If isolating shower stops overflow, fit a check valve on hot supply.

The first suggestion, getting a new tank is a bit drastic. Its more likely to be dodgy mixer taps. Not quite sure which tank you mean is overflowing though, or how the tanks are positioned.