On 1/22/2019 5:44 AM, Marland wrote:
Brian Gaff wrote:
Blimey this thread has a checked history over many years, but we when we
moved in here did not even realise there was a back boiler in the fireplace,
it was only later on when we needed a new hot water cylinder that the
plumber found it which had been disconnected and stop ends put on the pipe
it was still full of water and had not leaked after over 30 years. He of
course stuck a hose on a tap at the bottom and drained it. It was amazing
that we had not had a flood in those 30 years or so.
Maybe they made things a little better back in the 1930s!
If that is as exactly how you described it then whoever undertook the
original disconnection did exactly what should not be done. A drained back
boiler is just a lump of Iron or occasionally copper which will get very
hot which may or may not matter depending on what surrounds it, one full of
water and capped becomes a sealed pressure vessel and if it or bits of
capped pipe connected to it rupture under pressure then the results can be
nasty, low end is a split and you get a puddle for a while, high end is a
sudden explosive failure which could well be strong enough to cause a lot
of damage especially if it blows the contents of the burning grate into
the room over everything including occupants.

Ideally a disconnected back boiler and piping should be filled with sand
though if it is left uncapped pressure should not build up.

Mine was left uncapped, drained, had a number of holes drilled into it,
and was filled with sand.
And the new combi has saved a fortune in heating costs.