Thermostatic Radiator Valve Thumping

[David1983]

Good morning! Recently the thermostatic valve on the radiator has been thumping when it's been shutting off the flow into the radiator and to stop it I have either had to open it further or close it further, either one cures the thumping.

I have bled the radiator to no avail and I have also swapped the thermostatic head with one I know to be good from another room in the house. What is likely to be the problem - is it something with that radiator or indicative of a wider problem elsewhere in the house. The bathroom used to be the one radiator in the house without a TRV but that was swapped by a plumber with the radiator in the hall. If anyone can help I'd appreciate it. Thanks!

 

[simond]

It'll be a one directional valve and you will have it on the return rather than the flow.

Remedy is either changing it to the other end or buy a new bidirectional TRV.

Changing the head won't make any difference, as you have found.

 

[westbrom]

You should have one radiator in the house without a trv.....the bypass rad

if your plumber has put trvs on all of them then remove one either the hall one or the bathroom one and change the trv head valve to l/shield when you get chance.

If you have trvs on all your rads...this will cause this 'bounce"

 

[Statia]

Firstly, if you have TRV's on all the rads, don't bother with the effort of replacing one TRV with a lockshield valve, waste of time. Just take the thermostatic head off one of them, preferably the one which is in the same room at the room thermostat.

The bouncing is most likely caused by a uni-directional TRV being on the return rather than the flow, or it's due to the increase in pressure of the water in the pipework when many of the TRV's have already been closed off due to reaching temperature.

The TRV in our master bedroom made the bouncing noise after I installed another four TRV's on our rads instead of the lockshields. I replaced the pump with a smart pump which automatically reduces the speed of itself when the pressure goes up due to TRV's closing. Bouncing noise went away and I have a more efficient and quieter pump.

You can prove this quite easily by turning the pump speed down a notch or two when the valve starts making the bouncing noise. If the noise goes away, then a new smart pump is the answer. I got a Grundfos Alpha 2 and I think it's a cracking piece of kit.

 

[simond]

You bought a smart pump in preference to fitting a TRV the right way round?

And you think this is good advice

 

[Statia]

All my TRV's are bi-directional

Read my post properly

 

[David1983]

Thank you for the quick advice. I have a bypass radiator in the hall, I don't need to remove any TRVs from radiators. I've opened all the other TRVs up to maximum and I still get the bouncing on the bathroom one so it seems to me, and makes sense from what you've said, that it's been put on the wrong side of the radiator.

It was fitted by a plumber in the January but since I had no heating from Jan - Jun and then have been deployed to Afghanistan it's only the last fortnight that I've noticed it banging. Would it be fair to ask the plumber to come and take a look and if it has been put on the wrong side, to remedy it at his expense? I imagine that the CH would need to be fully drained down to do this I'm no expert.

 

[David1983]

To any professional plumbers reading this, if you'd fitted a TRV on the wrong side and the customer asked you to rectify your mistake as it was now thumping, would you?

I wish I'd spotted it sooner but I didn't get heating back until June and have since been deployed out of the country. After all, I'm trusting the plumber to do a good job and not to make mistakes.

 

[Timmyturtle]

Absolutely I would change it free of charge.My mistake=My problem

Wouldnt take very long anyways,probably without draining down

The Trv should have an arrow on its body telling you which way to fit it,if it is bi-directional it will have arrows pointing to both valve openings

 

[gasmick2]

i have had lots of problems on jobs with bumping rad valves even reverse flow ones , so i contacted the manufactureres and the said it was down to the lockshield valves not adjusted corectly, i did this and it cured it,
i am only talking about reverse flow ones not as other post have said
with regard to not having the old type fitted on the flow it does not work with those

mick

 

[David1983]

Hi gents, forgive me if this is a noddy question but the radiator valve has a single arrow pointing into the radiator and the valve is on the outlet side of the radiator. Is this likely to be the cause of the knocking as I've previously said that when it's knocking and I either open it or close it further the knocking stops. Just before I give the plumber who fitted it a call I'd like to be as sure as I can be. Thanks again for the good advice

 

[8aviashusband]

As the system warms up from cold (first thing in the morning, for example) check which end of the rad gets warm first. This is the 'flow', or inlet end. If your valve's on the other end, then that's why its thumping. The water needs to flow in the direction of the arrow on the valve body. It might be easier to change the valve for a bidirectional one than to take it out and fit it to the other end - but that's your plumber's decision.