cold water tank overflowing??

[rande]

I've just had a new cold water tank fitted in the loft it feeds 2 hot water cylinders, 1 for the 1st 2 floors, the other for the top 2 floors(showers etc) the problem is that after someone has turned a shower off (bristan thermostatic bar type) it flows back into the cold water cistern thus overflowing, the only thing i've managed to do to stop it so far is adjust the temp knob on the shower (which makes a thud like you've cut off the supply) & the water stops flowing back, whats causing it to do it in the 1st place??

 

[ChrisR]

Lack of non return valves on the pipes, unequal pressures and leakage inside the mixer. Put nrv's in.

 

[rande]

as far as i'am aware they all have them fitted in the shower unit themselves, but this did not happen before the new tank was fitted

 

[Nige F]

Get the plumber back ...stop the cheque.....get onto rogue traders

 

[Nige F]

sue Bristan