On 5 Oct, 14:56, "js.b1" wrote:
On Oct 5, 11:48*am, The Natural Philosopher
wrote:

disconnect back boiler and fill with sand.

Seal the piping too, because otherwise that can "plumb" CO to
undesired locations.

Hot water from a back boiler is such an insignificant factor its not
worth it unless you have a 24x7 fire like an Aga.

Back boiler piping sat in cold chimneys can burst during extremely
cold weather, one contributory reason for their demise when combined
with expensive wooden floors.

Definitely don't seal the pipes. If there's any water remaining in
the boiler it could explode if sealed and heated. Not possible to get
access to fill with sand.