When I was having some work done on my kitchen I asked the plumber to include re-piping a radiator (the pipes were under the plasterboard and went to a manifold above the ceiling.)
When I got home from work, the job had been done and he told me the pipes were completely clear but there had been some "gunge" in the manifold connection which he had dug out with a bit of wire.
I was wishing I had got him to look at another couple of slow radiators whilst he was about it - but I missed the opportunity of the ceiling being down. Now I only have limited access to the manifold via a hatch in the bedroom floor and certainly don't want to get a leak.
I have tried to use the mains pressure to flush out the blockages of these sluggish feed pipes (the return is clear) by opening the radiator drain with the return closed. I have also tried connecting a hose to reverse the flow.
The next attempt will be to put some good cleaner in the system and try to force it into the sluggish pipes by closing off the other radiators.
Ideally, I feel I would like to apply an alternating "blow / suck" to the pipe to try and move the blockage.
Any suggestion on a good cleaner and/or a good way to shift the blockage.