"Arfa Daily" wrote in message
...

Turn the boiler off.
Then turn the water mains off.
Do your plumbing.
Turn the mains on.
Flush the pipes by operating the taps.
Turn the boiler back on.

If you forget to turn the boiler off it may turn on and you get steam
shooting out of your cut pipe work if you are unlucky or worse if you are
very unlucky.