In article ,
"David WE Roberts" writes:
Just had a visit from a very friendly plumber, about replacing an electric
hob with a gas hob.

In passing, he said that he had just had to condemn an installation where a
Polish person had connected the cold mains to the gas part of the boiler,
and the gas to the cold mains feed.
He had told them they would have to call in the gas and water boards and it
would const them £7-8K to sort it all out.

My mind is still mildly boggling over the concept.
[And the £7-8K; I suppose it depends on how long they had it all turned on
before they realised the boiler wasn't lighting and they seemed to have a
lot of air in the water system.]

I am also wondering which is going to cause more problems - mains pressure
water in the gas main or mains pressure gas in the water main.

The former, particularly if it's gone back into the street gas main.
I would guess new meter at a minimum (even if it looks like it works,
calibration would need rechecking).

Gas pressure isn't high enough (anywhere near) to get back into the
water main.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]