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