Loud water inlet noise to combined boiler

[chrissybee56]

Any ideas gratefully received PSE. I have recently moved into a small semi which had a new combi. boiler fitted in June 2014 so is less than 7 months old. In the last few weeks, at random times, including during the night and waking me up (and the neighbours), what I can only assume is the water inlet to the boiler activates and the sound of water rushing in under pressure and then the loud clunk when the valve closes is horrendous. Its so Loud it overrides the sound of the television. It lasts for 20 seconds or so and can happen every 20 minutes or nothing for hours. The boiler installers are saying that this is not consistent with a combiboiler, it having no header tank etc and don't want to come and have a look. This is the first time I have had a combi-boiler so am not familiar with their workings but it doesn't seem entirely unlikely that this noise must be related to the boiler's operation, or does it? I have checked the pressure and everything else I can think of, has anyone experienced the same issue or could offer any advice,please?

 

[Newboy]

Probably better posting in Plumbing & heating.

What you describe isn't consistent with a combi-boiler operation.

I'd start by looking at what is connected to the mains supply - WC cisterns, water softeners etc and isolate each component until the cause is found .

It might also be worth checking if the noise is being transmitted from neighbours pipework.

As a start turn off your mains stopcock overnight and see if the problem stops

 

[chrissybee56]

Thanks. I'm nervous about turning off the supply in case it wrecks the boiler. Only the cistern is attached, there is no overflow evident so can't imagine why it would need to fill regularly. I know it is something to do with the mains in as everything is on the same wall, I don't think it's my neighbour's system. There are no other appliances other than a washing machine. Guess i need to get a plumber...

 

[The831Bunny]

Toilet flush valve dribbling down the pan is the common one. The level drops over an hour or two, then the cistern refills. Have a very close look down the pan for a slight trickle of water on the back of the bowl facing you.

 

[Newboy]

Turning off the main won't damage the boiler - don't run hot or cold taps when the main is off.

Check that the cistern is not trickling into the pan very slowly - that would be my favourite for the cause of the problem

 

[gigz]

As said it sounds like the toilet. When you say loud clunk ? Do you get this same clunk when you flush the toilet ? Also what make/model of combi is it ? Have had a few where the preheat kicks in every so often, during the day you probably wouldn't notice it, but during the night you would.