Can these deposits set hard in pipes? I have some in a section of piping in the ch system that I can't shift with X400 (in for a month) or flushing the system. Have been advised that it would be best to have offending section cut out by a plumber and replaced using compression fittings. The system is over 13 yrs old, and had not been drained before I did it 2 weeks ago. I know the deposits are there as a magnet sticks strongly to that section of pipe. It is in the airing cupboard where the feed pipe connects at the T piece to the horizontal section from the pump to the expansion pipe. Any advice welcome.

Jim, February 2009

Thanks derek, no good at plumbing stuff so a plumber it will have to be. I had hot water venting into expansion tank as well, must have cleared some of blockage as it doesn't do it so much now.
Thanks to gasman1uk as well for your comments.

jim, February 2009

I had a similar problem with my open vented system, the problem was so bad that the water was flowing up the vent into the header tank & the system was being re-fed via cold (now hot) water feed; solution was to remove the air trap unit [kind of cylinder with vent pipe on top & 15mm cold feed on 22mm pipe coming out of bottom side] with a new one..... whilst blocked, i had to reduce pump speed to minimum. I would get a plumber in to fix! [unless you are good at soldering!] B&Q have these traps mine cost me £24!

Derek Elsley, February 2009

they will set hard & u may get a blocked cold feed best thing to do is combine vent and feed as long as your boiler has o/heat stat

gasman1uk, February 2009