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How do I stop knocking radiator pipes I have identified the

Customer Question

How do I stop knocking radiator pipes
I have identified the radiator causing the problem and when it's switched off the knocking stops completely.
I have tried removing the air from each house radiator starting with the one nearest the boiler and tried increasing the pressure on the combi. Please help
Many thanks
Submitted: 11 months ago.
Category: Plumbing
Expert:  Andrew Smith replied 11 months ago.

Does it have a thermostatic radiator valve?

Customer: replied 11 months ago.
it does, when the valve is turned down to 0 knocking stops
Expert:  Andrew Smith replied 11 months ago.

It is the valve at fault and will need changing - it is hammering against the flow of water.

To use it until you get it swapped then either run on full or off

Customer: replied 11 months ago.
Sorry forget to mention replacing the radiator valve on two of the radiators I thought were first at fault was one of the first things I did and it made no difference.
Radiator in question (bedroom) has a brand new valve on.
Also, since turning the pressure up this morning the knocking is now incredibly worse, every 5-10 mins now but before it was only when combi fired up and timer went off.
And what makes things worse is the radiator I thought was doing the knocking (bedroom) has been set to zero all day. Does this mean a different radiator is causing the knocking. We have a towel radiator in on suite bathroom with no rad valve. The bedroom and on suite radiator were the only two that let air out when I bled them yesterday
Expert:  Andrew Smith replied 11 months ago.

I think you may have to go around the house and turn them off one at a time to find the faulty one.

I think you are unlucky that they have started acting up, but they all tend to go at the same sort of time once they have been in for 10 years or so.

Customer: replied 11 months ago.
just to confirm you definitely think it's a faulty rad valve causing the knocking?
Could it be the towel rail in en suite bathroom or not ?
And do I turn the valve down zero or remove the valve altogether?
Expert:  Andrew Smith replied 11 months ago.

If you turn the valve down to shut it off or turn it right up it will stop banging until you get them swapped

Customer: replied 11 months ago.
I will be replacing all the trv's tomorrow on x4 radiators so will let you know if that solves the problem
Expert:  Andrew Smith replied 11 months ago.

No problem

Customer: replied 11 months ago.
Switched heating off at 6pm. Installed four brand new trv's at 6.30pm. Turned heating back on just now, knocking seemed louder than normal.
Please advise
Expert:  Andrew Smith replied 11 months ago.

Can you turn off the radiators one at a time?

Customer: replied 11 months ago.
Knocking is intermittent and it mainly happens when heating comes on and goes off. Do you want me to test this over the next few days turning each radiator off in turn?
Customer: replied 11 months ago.
Sorry did you want me to turn off the four radiators now to see if knocking continues ?
Expert:  Andrew Smith replied 11 months ago.

Yes, no rush - lets work our way around the system

Does the pressure gauge needle vibrate when this occurs?

Customer: replied 11 months ago.
just checked and the needle does move backwards and forwards slightly when heating turns on.
For the past few days I have taken it in turns the switched each of the four radiators off when heating comes on. It made no difference, still knocks each time.
This leaves one small radiator which doesn't accommodate a trv, another one which just has trv missing and a towel rail.
These are the ones I've not touched.
Expert:  Nicola-mod replied 11 months ago.
It seems the professional has left this conversation. This happens occasionally, and it's usually because the professional thinks that someone else might be a better match for your question. I've been working hard to find a new professional to assist you with your question, but sometimes finding the right professional can take a little longer than expected.
I wonder whether you're OK with continuing to wait for an answer. If you are, please let me know and I will continue my search. If not, feel free to let me know and I will cancel this question for you.
Thank you!
Customer: replied 11 months ago.
OK to continue to wait
Many thanks
Expert:  Nicola-mod replied 10 months ago.
We will continue to look for a Professional to assist you.
Thank you for your patience,
Customer: replied 10 months ago.
Please advise what is happening here?