Hi,

I'll be doing some work on the kitchen in the near future, and having
moved things around to measure them I have found that the gas pipe to
the cooker is in very poor condition - it is buried under the concrete
floor with seemingly no protection and at the point where it exits the
floor it is very green and corroded looking. I am assuming that I have
no other option but to replace it (tell me if I'm wrong to save me some
work!) Am also planning to replace cooker with gas hob/electric oven.

While I'm at it, I'm going to upgrade the pipework to the boiler to 22mm
as it is currently only 15mm.

The gas supply and meter come in to the front of the house in a cupboard
in the living room. The kitchen is in a single storey extension at the
back. My options are as follows:

1) Take 22mm pipe under living room floor (this isn't concrete, only
the extension is) from meter, up through the cupboard where the boiler
is, T off to boiler with short lenght of 15mm. Carry on up the cupboard
with 15mm to under the floorboards on the landing. Take it accross the
landing, through back bedroom and down into dining room where it will be
boxed in vertically until going through the wall into the kitchen roof
space. Then down through the ceiling to below hob height, across the
wall behind the units and into hob.

My main question relating to this option is what I am supposed to do
when running the pipe through the wall into the extension. I know that
you are supposed to sleeve the pipe and only seal it at one end - but
which end? If I seal it at the house end and there is a leak it will
spill into the roof space of the extension which is enclosed so would
allow gas to build up - if I seal it on the extension side then it will
build up in the boxing in on the house side. Any ideas what would be
best?

2) Dig up channel in kitchen floor to replace the current run of pipe.

Not sure if this is easier or harder - I'm assuming my trusty SDS with a
chisel bit would make fairly light work of digging up the channel
(probably cut the edges with an angle grinder) - but how do I go about
filling it or covering it afterwards? I would preferably cover it with
wood as opposed to refilling it to aid future access.

Any adivce/ideas/criticisms on the above would be greatly appreciated.

Thanks,
Richard