Avoid copper coming into contact with plaster - the plaster will
corrode it if any moisture is present, and water pipes (even heating
pipes) will get condensation on them at times. I sleaved 15mm copper
pipe in 20mm plastic electrical conduit when plastering into a wall,
and you can apply small bends to this combination with a 22mm pipe
bender (20mm electrical conduit bender would probably work even better).
This also allows for the copper to move a bit as it heats and cools.
Yes I'd intended to wrap the pipes in denso, secure them with pipe
clips, then cover the hole with a layer of expanded mesh steel and
plaster over that. Some have said that putting pipe into a plastic pipe
will lead to clicking - have you noticed that?
This is standardly done when installing underfloor heating in concrete.
Indeed it should be pressurised whilst the concrete sets, so the pipes
don't later try to expand more than the original holes they formed in
I pressure tested all the sections of my central heating as I went.
I did it dry which is potentially quite dangerous - if something does
fail and blow apart, the energy release can be considerable and
explosive and people can be injured, so I made sure I was the only
person in the house when doing it. The advantages are that air leaks
much faster from any leaks so you can find smaller leaks than you can
with water, using gas leak detector fluid (froths up), and if you need
to resolder anything, the pipework is still all dry.
Strictly speaking, you should fill most of the system with water when
pressure testing, and just have a small plug of air which is compressed.
This is because the energy stored in the system, and the potential for
explosive release of it, is very much reduced. This is what H&S
but it is not so effective at finding small leaks, and more difficult
to do on incomplete sections of the system.
I did similar, but actually started with the boiler and just the
bathroom radiator. Next came the upstairs heating zone, and finally
(a year later IIRC), the downstairs heating zone.
Did you have any issues getting a heating eng to install a boiler and
then leave you to do the radiators? I'd assumed they'd want to see a
full set up of rads and pipework, prior to installing the boiler.