Feel a bit sorry for one of my neighbours, youngish family that have been flooded twice with flooring ruined both times because rat(s) got in through the washing machine outlet and burrowed through pipe to get to the ktichen. I got involved and despite my experience the fecker took an age to...
Simon,
If I read the thread correctly and I think I did, you'd already cleared the blockage but criticise Oz for his advice not being very useful when infact he's answered your query (post #4) precisely.
"Well I've managed to clear the blockage (getting a coat-hanger in there was most helpful in the end) but connecting it back up, there's a leak...
Am I supposed to use some sort of adhesive? Thanks!"
Everybody agreed the best remedy would be to replace the pipework but it was the first plumber that was paid and left the leaks/his fix unresolved. The bodge recommendations (mainly from me) were for a relatively unskilled but willing home owner to get out of a temporary bind when no plumbers...
It's multi purpose and works well as either afaic. They are both low modulus perhaps not as low as Gold perhaps which is why you can break it easily but low enough for sealing joints.
As above I'd modify a stock rubber washer by making a mandrel out of 10mm bolt/stud, nuts and washers and stick in your drill to use like a lathe. Shape it with a rasp, file, emery board or whatevers handy.
System boilers have a pressurised heating circuit like a combi so I doubt it's that. More likely those leaking combi installs were power or chemical flushed and that might've upset some already weak or poorly installed/insulated underground pipework.
I looked up the faults out of curiosity as I was unfamiliar with this boiler and there wasn't anything unusual that a competent engineer (not plumber) shouldn't be able to sort.
We can't legally encourage you to repair your own boiler.
Are you the home owner and if so when was it last serviced and what work to remedy this problem has been carried out?