In article .com,
"Jyestyn" writes:
A collegue of mine is due to lose his mains water supply later
this week (Thursday) during essential maintenance by water
authority contractors. The water will be off from 08.00 Thursday
until 20.00 on Friday this week. The works involve replacement of
the complete water mains supply pipework in the street, up to the
individual valve outside each property.

His house is fitted with a combi gas boiler. He is unsure if he
will be able to run his combi (for heating only) whilst the water
main is off. I am unable to answer this question, I am not
a combi user myself.

Combi should continue working fine for heating. It would probably
be a good idea to switch off its hot water facility whilst the
work is going on so pressure changes and air in pipework don't
cause it to fire up, and/or switch off the water at the mains.

--
Andrew Gabriel