In an earlier contribution to this discussion,
Bob wrote:

Hi,

I have a problem with my central heating system, which I hope someone
could advise me on. I'm not very good with plumbing, so if I am
lacking info, please forgive me and ask for more details.

Anyway, My central heating pipes/rads make quite a lot of noise of
running water, particular upstairs and in the pipes going to upstairs.
The radiators upstairs are a nightmare. One of them is relatively ok,
heat-wise, but it needs bleeding every 2 or 3 days. The other
radiators are cold and appear to be empty. If I open the bleed valves
on these with the thermostat set so the pump and heating is running,
then water drains from the radiator (I can feel suction on the bleed
valve.) If I turn the thermostat so the heating is off, the radiators
fill up, but when they are full, they are still cold (getting full
with cold water??) Sometimes, through bleeding all rads at the same
time and then switcing the bleed valves off, I hear running water,
then the header tank overflow pipe starts spilling water. And that's
about it, I'm not sure where to begin to look.

Does anyone have any ideas or suggestions. I'm quite prepared to call
a plumber out if that's what's necessary, but I'd prefer to know what
the problem is before I did that so he can't try pulling the wool.

Many thanks for reading,
Bob

Has it ever worked? Has this problem arisen since someone did some
alterations or repairs to the system?

My first thoughts are that the pump is pumping in the wrong direction - and
needs turning round. But we really need more details of the system type.

Are both heating and hot water pumped, or is HW primary circulation by
gravity (convection)? Are there any motorised valves? If so how many, and
does each one have two or three water connections? [Photos of the pipework
in the airing cupboard - if that's where the valves/pump are - would be
useful].

Which header tank is overflowing - the large cold tank which feeds the
domestic hot water system, or the small tank for the heating system? If it's
the small one, is the ball valve working ok? What is the water level when
the system is cold? [There should be only 2 or 3 inches of water in the
tank - with the level a *long* way below the overflow to allow for
expansion].

That'll do for starters!
--
Cheers,
Set Square
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