Combi boiler - whirring noise when hot water ran

19 Jul 2010
Reaction score
United Kingdom
A general question here for anyone who can please help?:

Combi Boiler - when hot water is ran, it makes a whining noise. Not when heating is on (tested it) - hot water is ok though, it;s just the noise.
What could it possibly be

(Biasis combi) Been here for the 7 years + I've lived here.
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The poster clearly thinks that he has a better idea of what the fault is so I have decided that it would be better for me to delete my advice to him.

Obviously I have not seen his boiler and only have what he has said to go on. But as I fix boilers every day I would expect that I am likely to have a better idea of what the problem is going to be.

Apologies to those who use these forums to learn about boiler rapairs.

Thanks for your help

I was thinking maybe diverter valve was faulty?

Main heat exchanger ? - But in heating mode it is fine??

How would the flow restrictor cause this noise?

Sorry I don't know the model
I have told you what the likely cause of the problem is.

However, you have decided to ignore what I have said and decided to list your choice of possible faults.

Obviously you imagine that you have a better idea of whats wrong than a professional who fixes these boilers every day.

When its working again tell us which of the items on your list it was.

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Agile - sorry if I offended you, I was just trying to understand why a flow restrictor could cause the noise. If I undertsand why it helps when trying to diagnose/repair the problem.

I only mentioned the iverter valve due to it being mentioned to me before....

Thanks for your help and sorry once again.
You have not offended me.

However, when somebody asks about a technical problem, I expect that they are wanting advice from somebody with professional experience of boiler repairs.

When they reply in the vein of not accepting the advice given, because its not within their understanding, then it makes me feel that I should not have given them any help. If you ask for advice then you should be prepared to accept it.

Its obviously up to you if you take advice or not, but when you reply suggesting something like the diverter valve which is not involved, then I will think that you imagine that you know more about boilers than I do and dont want my advice.

I'm amazed by the number of people who ask for help and advice, only to try and argue about it :rolleyes: :confused: :eek: :evil:
Ok, fair enough. I apologise agai and would be very thankful for our advie.

How would I go about checking the flow restrictor please?
See if it still makes the noise when power to the boiler is switched off.

Start running the hot water and have it making the noise then turn off the power to boiler and see what happens.

Thanks Agile, really appreciate your help/advice.

I have done what you said and the noise doesn't happen with the power off (switch at spur turned off)
In that case the flow restrictor is rulled out.


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