Central heating pipes whistle when heating not being used

[Ric2013]

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.

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.

 

[skoronesa]

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.

 

[chris watkins]

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.

What we would call injector tees (or swept) on a one pipe system ?

 

[Ric2013]

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.

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?