Radiator noise

[asalcedo]

The central heating in my house works very well, but there is a problem. When the pump is working some of the radiators make noise.

Other radiators are silent.

It is not a humming noise, but a noise of water flowing. Akin to the noise of a stream of water in the mountains. It is somewhat loud, especially at the beginning of the pump running.

I thought it might be due to air in the system, but all the radiators are fully bled.

The system is a sealed one with plastic pipes and aluminium radiators. It has been powerflushed well and inhibited.

Any idea of how to resolve this?

Thanks,

Antonio

[Stephen Mawson]

I have had this problem, caused by nearly-closed thermostatic radiator valves. Do you have them and, if so, does the noise stop when you open them fully?

Stephen

[Peter Kemp]

I'm not the OP, but (a) I have exactly the same problem and (b) yes, I do have some mostly-closed TRVs and the sound does indeed diminsh/stop when I open them fully.

Am I doomed to having them open and wasting heat (albeit with a quiet system), or is there a Cunning Plan?

Thanks - Peter

[Roger Mills]

Some TRVs are directional, and *mind* which way the water flows through them. If fitted the wrong way round, they are noisy. So check yours, and put them at the opposite end of the radiator if they are wrong.

[Or swap them from vertical to horizontal (or vice versa) if they are the type with two compression joints at right angles. Or, if they're the sort with a moving bit inside which allows the flow direction to be configured, move that to the other position].

Unfortunately, all of these remedies require a certain amount of system draining.

[RobertL]

You can add a chemncial to reduce the noise. Even normal inhibitor reduces the noise quite a bit, but presumably you have that already.

There can still be a pocket of air in the rads, even when fully bled, because the bleed screws are not usually right at the top.

Robert

[Roger Mills]

Yes, but the noise I was talking about is not related to air, but occurs when water flows through 'directional' valves in the wrong direction, and gets the innards vibrating.

[asalcedo]

Hello Robert,

I am with you, inclined to believe that pockets of air are the cause.

The system is inhibited to manufacturer's specifications, as per the Sentinel Quick Test.

I do have a chemical for boiler noise, but since the noise is not from the boiler I have not added it.

I do not have TRVs and all valves, except for a couple for balancing (that do not make noise) are fully open.

The fact that some radiators are dead quiet and others are not, all other things being equal (lack of TRVs, valves fully opened) and the fact that the noise is not a humming noise (like the one when a TRV is the wrong way around or valves are not fully open) makes me believe that there may still be some air trapped as the most likely option.

The question then is how to get that air out of the system if bleeding the radiators is not helping.

Thanks,

Antonio

[John]

I have got one as well. The radiator has some sort of restriction as it takes ages to get hot - even though every valve is open. When I took the radiator off to decorate I found a restricted flow out of the return pipe. ( I was just checking - I did close the valves!)

[asalcedo]

One further piece of information: For the radiators that make noise, I can reduce or even eliminate that noise if I close one of their valves two to three full turns (still three to five turns left to fully close them).

In other systems, as other posters have said here, usually the opposite happens, i.e. noise goes down when opening the valves....

John;2313927 Wrote: