Condensation around shower mixer

[momossy]

Hi Ive just installed a new shower and Ive noticed excessive constant condensation around the two feed pipes and the mixer bar of the shower. Its fed by a separate cold supply from the garage and the hot via a non vented tank. No-one uses the shower at the moment. Could this be excessive cold pressure entering the hot system via the mixer ?

 

[terryplumb]

Are the hot and cold pipes surface mounted (visible lengths)to the mixer ?

 

[momossy]

No they are in a stud wall and come trough that to the mixer. Ive discovered that when I switch off the hot feed to this bathroom and then open the hot basin tap or shower hot then cold water comes through these taps. Does this mean that the cold mains pressure is too high and forcing its way across the shower mixer and or mono tap ?

 

[terryplumb]

Could well be. If cylinder is UNvented ( under mains pressure) and is isolated , but you still get cold water, flowing under pressure, from hot outlets,that is indicative of cross flow.

 

[momossy]

Thanks Terry yes its an unvented HW tank. Its a little complicated in that this bathroom is above the garage so gets the hot via the non vented HW tank but the cold is from a separate main to the main house in that its the hosepipe /external tap to the garage.
Its not basting out of the HW tap more of a good trickle filling a cup in 30 secs

 

[terryplumb]

Fitting non return valve to hot supply pipes to basin / shower etc would be required