Boiler firing up when cold tap turned off

[on31ll]

Posting in here because i know the rules on gas info etc i am not after gas advice just i remeber it maybe being solved with a pressure reducing valve or somthing ?

As the title says really new boiler but new water mains at the same time ! So really just after what could it be ? Heard of it before ? Boiler is a glow worm

 

[stevetheplumber]

think you need a non return valve on the main its bouncing the diaphram when you shut the cold tap you need to stop the shock wave getting to the boiler

 

[Poxi]

Normally a hot water dead leg somewhere..i.e a piece of exsisting hot water pipe that has been capped and not in use anymore, if this is the case and there is a compression cap on it undo it gently until the air stops and water comes out

 

[Destroyer2813]

What about a little shock arestor vessel instead of a nrv Steve

 

[on31ll]

Thinkin about it there might be a small dead leg on hot and cold ! Will trim that back ! If it still happens will fit nrv ! Cheers boys

 

[mountainman]

Depends on the boiler but it could be the preheat doing it's job.

 

[vern]

Posting in here because i know the rules on gas info etc i am not after gas advice just i remeber it maybe being solved with a pressure reducing valve or somthing ?

As the title says really new boiler but new water mains at the same time ! So really just after what could it be ? Heard of it before ? Boiler is a glow worm

What boiler is it? If WB CDi this can be dialled out in a software setting very useful

 

[SafeGasInstall]

What about a little shock arestor vessel instead of a nrv Steve

i would say fit nrv and a little vessel after it together in line

 

[Mike Jackson]

I agree. What happens is when the cold tap is turned on water pressure reduces slightly and water is drawn back out of the boiler. When the cold tap is shut the pressure increases and there is a small flow back into the boiler which activates the flow switch. A NRV will solve this problem but you then have the issue of not enough pipework to take up the small expansion of water when it is heated so have to fit the shock arrestor to prevent over pressurisation of the hot water side of the boiler.

 

[on31ll]

Boiler is a glowworm !

 

[vern]

Boiler is a glowworm !

oh! unlucky:tongue:

 

[on31ll]

Ha ha cheap and cheerful ! Does the job ! And price paid for it is cheaper than one repair on a eb or valliant ! Its the mothers anyway !