Mains cold taps hammering, opening hot outlets stops it

[sw89]

Now then fellas, just signed up as im abit stuck with a job at a tenants this afternoon, for a month or so since they had their new boiler fitted (Vallient ecotec +824) all the cold taps in the property hammer when theyre opened , which in turn causes the hot taps to kettle up and begin to pass hot water through them, opening the hot tap stops the kettling/hammering. I was sent there to replace the kitchen taps but i dont think that wouldve made any difference to this problem and its highly unlikely all the taps in the flat need replacing at once... Any other ideas possibly boiler related? Cheers in advance

 

[ShaunCorbs]

whats there incoming pressure at?

 

[Ch4 plumbing]

Is their a water metre fitted (double check valve)?

Good idea to fit a shock arrester, that's assuming pipe work is clipped well.

 

[ambrosia]

the hot is mixing with the cold somewhere, new boiler could have been piped up wrong or its a mixer tap/shower
try experimenting with the isolation valves you have access to, start with cold feed to the boiler, turn it off and see if you still get water out of hot taps

is there a thermostatic shower, this type of problem often leads back to a thermostatic shower

 

[kris]

Id put money on a mixer shower gone. I understand the hammer but I'm not following the kettling. Is the hammer bringing on the boiler?

 

[Ch4 plumbing]

The water hammer is probably pushing up into the boiler via the cold feed and firing the boiler that way.

 

[RoyalCrabs]

Sounds like double check valve issue, take it out / apart and retry or just replace.