"Chris B" wrote in message
news
On 16/08/2018 20:44, Tim+ wrote:
The hot water system is just a €śthrough the boiler/heat exchanger€ť system
so just turn off cold inlet to boiler, change washer, job done.
No, its the 185 lt of hot water in the pressurised cylinder I'm worried
about......
Turn off inlet rising main somewhere before it feeds into the cylinder. Run
hot water until no more comes out of the tap that you want to change. There
is now no nett pressure in the cylinder. Since the outlet from a cylinder is
always at the highest point of it, there won't even be a tendency for water
to siphon out of it - even supposing that air could enter to replace the
water which was lost by siphoning.