In article ,
raden writes:
In message .com,
Martin Pentreath writes
The service manual does indeed say "the boiler must be drained of all
water", but that's all it says, it doesn't say how to do that.

... Because not every boiler is installed in an identical fashion

There should be valves to isolate the boiler, then you have to use a bit
of grey matter to find where best to break the circuit

....bearing in mind the pressure vessel (which is presumably in
the boiler) is going to squirt the water out either straight
in your face or over the electrics inside the boiler, if you
are not careful. There may be a drain point inside the boiler
to release the pressure and water in a more controller manner.

--
Andrew Gabriel