asalcedo wrote:
I need to add a couple of tees to a sealed central heating system.

It is a large one with more than 400 litres of water in it.

I am thinking of leaving some large radiators full of water by closing
both valves in each of them and drain the rest of the system. Then cut
the pipes and solder.

By leaving some radiators full of water I save time (shorter draining,
less venting etc.), water and inhibitor.

Can this be done or will I run the risk of unexpected water ruining the
soldering?

Do you have to solder? For grafting bits onto an existing system, I find
that a service valve (full bore) and a pushfit fitting of some sort
(cuprofit look almost as neat as capillary) will let you cut into a
"live" system and not lose more than a cup full of water. You can then
extend at your leisure and use the valves to finally bring the new bit
online.

--
Cheers,

John.

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