Main Combi 30 HE boiler with noisy DHW pipes

[stuart_rambo]

Hi All, after some advise please. I have a Main Combi 30 HE boiler. its been in working fine for about two years. then two days ago i have started having pipe banging /chatter when demanding hot water. I'm trying to figure out where the noise is coming from. but as the house is decorated i need to try and narrow it down before taking carpet up.

got a few questions
1) is it normal for boiler to fire up momenterailay when cold water taps are actuated? this has happened from new. any of the cold water taps, or after toilet fill valve finishes. the boiler boots up hot water? for maybe 3 to 5 seconds.
2)the pipes bang when the boiler starts producing hot water (so also bangs when cold water taps are actuated)
3) what would be the best way to try and narrow down where the banging is coming from?
4) how urgent is it to fix the issue of pipe banging?

thank you for any help.

 

[stevetheplumber]

you need a non return valve and a shock arrestor
by the sounds of it but strange to have started after two years has anything else changed?

 

[stuart_rambo]

Hi Steve , thanks for sparing your time. Nothing else has changed. Just came home one night last week and noticed the unhealthy sound. Just looked, boiler was fitted three years ago. Two years ago had a new bathroom - bristan taps and thermostatic bar shower tap.
Very strange. Will try and replace the full flow isolator for a non return valve. See where that gets me.
Is it safe to say the boiler shouldn't ignite (even for only a short period of time) when cold taps are opened?

 

[REDSAW]

strange that!

did the same boiler and same bristan taps with the same fault last week!!!

your not in nottingham are you?

well, cant be i fixed that one lol.

 

[stuart_rambo]

Nope. Birmingham. Any chance you sharing the fix with me please?

 

[Billy Bob Bob]

Nope. Birmingham. Any chance you sharing the fix with me please?

sounds like you have a dead leg on the hot,water been off recently and work done elsewhere on the mains?

 

[REDSAW]

Nope. Birmingham. Any chance you sharing the fix with me please?

same as steve said is required within a meter from the boiler..cold flow is lashing back and forward causing flow switch register.

http://www.showerdoc.com/reliance-potable-water-shock-arrestor-0-16-lt-5-0-bar-1-2-mbsp-xves-050-000

 

[stuart_rambo]

Thanks for your help redsaw. Much appreciated.

Hi gas man, not that I'm aware of. However it's a Victorian terraced an we have four properties from the same stop valve. So whether anything happened whilst I was at work I don't know

 

[Billy Bob Bob]

Thanks for your help redsaw. Much appreciated.

Hi gas man, not that I'm aware of. However it's a Victorian terraced an we have four properties from the same stop valve. So whether anything happened whilst I was at work I don't know

if the hot pipe has been capped somewhere where there is no flow(old airing cupboard for example)and the water has been off,it will now be full of air,causing your problem,you either need to find it and bleed it or fit a mini arestor

 

[stuart_rambo]

Gas man. You are a legend. When upstairs was done they ran tails in to the loft for an extension. Mall I got to do is determine which pipe is which. Thank you.

 

[stuart_rambo]

It took the air out the hot and cold water tails in the loft. Sadly it made no difference. Still get the pipe banging when boiler starts up for DHW. Will try the nonreturn valve and shock arrestor at weekend hopefully.

 

[Julie Street]

Hi Stuart, can you share whether the shock arrestor solution worked?
Cheers!

 

[thompsonbrown]

Sounds like a mains water pressure problem. 4 houses of 1 mains supply. Check to see if any of the other properties has had work carried out recently and if the water mains was turned off. Your boiler might be firing up due to decreased water pressure to the hot water flow switch when a cold tap is turned on, then re-energized when the water pressure is stabilized.