I'm trying to decide on the best course of action with our house. We have about 4 radiators downstairs, 4 upstairs. Back boiler. Central heating is one of those ones that has a header tank in the loft (low pressure?)

Pipes and rads gurgle like mad. Downstairs ones are mostly fine and bleed pretty much when you crack the valve. Upstairs the bathroom was half empty, bedroom 3/4 full, and then two other ones were nearly totally empty, though the pipes going to them were hot.

I don't think they'd been bled at all by the previous owners.

Issue is I think they're all a bit gunged up, you can take the bleed valve right out and there's no kind of pressure or flow of water coming back in to the radiator. The thing I'm most concerned about is that it looks like when the CH turns off, and the rads cool, the header tank seems to be filling up a bit causing the overflow pipe to kick in. My concern is if that overflow pipe got blocked/frozen, the header tank might overflow and leak through the ceiling.

My best guess is that there's a chunk of gunge somewhere in the upstairs rads and/or near the header. Normal expansion from the heat pulls a slow trickle of water from the header, and there's some kind of micro-leak sucking in air too. When the heat goes off, the contraction and additional air in the system is pushing the excess water back to the header.

I've read about draining the system, which I've never done. I'm a bit concerned that if there is a blockage, I'll drain the system and not be able to refill it.

Local plumber has quoted £22 per rad to powerflush/de-gunge them. I've seen de-gunk products in B&Q for about £20 too. Assuming the B&Q stuff would do more than 1 rad per bottle...

for £200 I would get a plumber to flush & re-balance the whole system.
It will save you money in the long run, both in energy (as the blockage must be reducing efficiency & causing your boiler pump to work harder) & if something breaks because of the blockages.
Also balancing should mean the whole house gets hot at the same time, rather than 1 room being roasting hot (usually the front rads on the loop) & other rooms staying cold.


If you got an old boiler & something does break - chances are you wont get parts. That means a new boiler.... $$$££££$$$


Also, I think the header tank works like a cistern, so a ball on an arm controls the water filling.

TRV's can jam if they have been closed for a long time.. a careful tap with a hammer on the valve body can free them.

p.s. to balance a heating system, you need to wait till it's cold

then turn off the taps on the other end of the radiator (the tap you don' normally turn) then turn it back on 1/4 of a turn...

turn the heating on and see which radiators get hot and which ones don't.... once the system is warm, check for any radiators which are colder than the others... any cold ones, open their tap an extra 1/4 of a turn.... wait and repeat till the system is balanced :-)