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Central heating pipes whistle when heating not being used

Discuss Central heating pipes whistle when heating not being used in the Plumbing Jobs | The Job-board area at PlumbersForums.net

J

james coutts

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I have a combi boiler, recently one radiator has started whistling , the heating is not on nor is the hot water being used ,I have done everything liking bleeding , cleaning and draining the whole system, checking the pressure in radiators, and changed the lockshields on the whistling radiator , which has a lockshield on both sides (no TRV ). When I removed the radiator to replace Lockshields the pipe from the floor continued to whistle while the radiator was not connected.. the whistle can go away for hours the comes back for no obvious reason...can anyone help ???
 
If it is a flat, how do you know it is being caused by your heating?
Could it not be resonating through your Heating pipes but originating elsewhere?
Maybe when your Heating is on, the vibration is enough to alter the sound or even prevent it.
I am guessing because I have not heard it obviously but just thought I would ask if that might be possible. It might make you think outside the box a bit too.
 
Last Plumber said:
If it is a flat, how do you know it is being caused by your heating?
Could it not be resonating through your Heating pipes but originating elsewhere?
Maybe when your Heating is on, the vibration is enough to alter the sound or even prevent it.
I am guessing because I have not heard it obviously but just thought I would ask if that might be possible. It might make you think outside the box a bit too.
Click to expand...

You could be right, only I have not a clue where it originating from, I have checked every possible place I can think of and the only thing I know is , it comes from the same one radiator all the time , (it's the first radiator from the boiler) I removed the radiator to change the lockshield ( thought that was the problem) and the whistling was coming out of the pipe on the floor, and I can't trace it back to one particular place , it only comes when the heating has been off for more than a good few hours ,I have to put the heating back on to make it go away. I really appreciate your help , I will check everything again maybe something will jump out this time.
 
One of the radiator sections has a bad seal. When the system cools it is pulling a vacuum and sucking air into the radiator. When it heats up the vacuum stops. It doesnt leak water because the caulking swells and amy moistureevaporates leaving no trace.

Next time you hear it take some oil paint and paint the cracks where the sections come together. Then it should suck in the paint and seal itself.
 
skoronesa said:
One of the radiator sections has a bad seal. When the system cools it is pulling a vacuum and sucking air into the radiator. When it heats up the vacuum stops. It doesnt leak water because the caulking swells and amy moistureevaporates leaving no trace.

Next time you hear it take some oil paint and paint the cracks where the sections come together. Then it should suck in the paint and seal itself.
Click to expand...
Nope. The OP has stated the noise continues when the radiator is removed, and UK systems do not have a vacuum when cold (unless it is a very unusual system). Also very rare to find sectional radiators these days.
 
Right, I forgot you guys have what we would call atmospherically vented systems. We too have one piece cast iron radiators but most modern residential radiators sold here are sectional.

Is the whistling air or water? Here we have monoflo tees which sort of scoop some water from the heat pipe and sends it off to the line for the radiator which in turn ends up in another specially designed tee fitting to dump it back into the main heat loop.

At least that's the old way of doing it. If he has this same setup maybe one of the tees has some sediment built up causing the water to cavitate/whistle as it flows.
 
skoronesa said:
Right, I forgot you guys have what we would call atmospherically vented systems. We too have one piece cast iron radiators but most modern residential radiators sold here are sectional.

Is the whistling air or water? Here we have monoflo tees which sort of scoop some water from the heat pipe and sends it off to the line for the radiator which in turn ends up in another specially designed tee fitting to dump it back into the main heat loop.
Click to expand...

Most systems are pressurised well above atmospheric pressure, though many atmospheric systems (open-vented) live on. Most radiators are pressed steel with no joints: cast-iron or aluminium, sectional or otherwise, is either legacy or designer.

There is no flow when the radiator is removed. Also the OP has claimed the noise persists even if the electricity supply is isolated, so I think we can rule out flow-associated whistling - the only flow there could be would be a result of convection currents within the system.

I realise you are trying to help, but would you please read the OP's posts carefully before replying again, otherwise this is all a tad futile?
 

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