Re-lining a gas pipe. I have questions!

I would guess that they are actually using a mole to dig a tunnel which they are then pushing the new plastic pipe though. Later on they will make each connection to the individual houses. Think the mole needs an 800x800 pit to start. The original metal pipe will be abandoned.

They usually put the plastic pipe inside the old original pipe. So they cut it at the meter end and feed it in. I don’t think they need access to the house or meter or dig holes in your garden unless something goes wrong

We had our meter moved so I know ours was relined at some point On the outside it was the original steel with the old hair seals

I would guess that they are actually using a mole

I haven't seen a moling machine, that doesn't mean there hasn't been one though.

The inquisitive hound and me will check it out in a bit on our walk.

EDIT: Also moling right next to a gas main seems dodgy?

My road & surrounding streets are having the gas pipes replaced,

Good luck.
We've just patiently watched the electric supply be replaced down our road and connecting lane. 8 weeks to do 600metres.... There's a lot of things hiding underground in a 1970's estate built on an old railway line and sidings. It's slow.

When they did our old street they turned the gas off for a few hours to reconnect and test. Can't remember much, if any, digging out from the main pits so don't know how they did it.
Biggest concern at the time was the fact that the guys digging and fitting gas pipes had no issues chain smoking down in their pipe holes. The guy from British Gas / Centrica didn't look happy when we asked him whether it might not be wise. Seemed he had little control over the Murphy contracts team.

As said above, the main pipe is pushed up the old cast iron pipe and then reconnected. The holes outside each house are or should be were the old pipe connect's to the mains, usually we would try and insert the new pipe up the old one to the meter. It's then connected to the meter at the mains end, you then smash the cast iron pipe around the new pipe and weld/melt a valve to it. You then connect the house service pipe to the valve and pressure test to make sure there are no leaks, if ok the valve is then dilled through to the mains.

Good luck.
We’ve just patiently watched the electric supply be replaced down our road and connecting lane. 8 weeks to do 600metres…. There’s a lot of things hiding underground in a 1970’s estate built on an old railway line and sidings. It’s slow.

I've already decided it's going to take ages, I know how these things go! So far it's not really disruptive though, the roads are pretty wide and it's mostly contained on the pavement/grass verges. We'll see though once they start digging holes infront of every house...

So pupster didn't want to walk where the work was being done so we went the other way and peered in to a hole.

It's definitely relining the original pipe, there's a T junction uncovered where a section of the original pipe has been cut and there's nice new yellow pipe inside with a decent looking seal around it, so I assume the original pipe is still live with gas around the outside of the new smaller yellow pipe.

I think @integra has answered the how to connect question, I'll expect a hole outside my house soon 🙂 Is that done with the gas still on? I know for water you can connect around the pipe then cut into the main pipe without turning the water off, seems a little more dodgy for gas...

I've worked with companies relining drainage pipes. They send a robot down the pipe and it scans all the joining pipes. Once it's relined it retraces its steps and cuts out the holes to match the junctions. It's basically voodoo, no idea if the same tech exists for smaller bore pipes.

there’s a T junction uncovered where a section of the original pipe has been cut and there’s nice new yellow pipe inside with a decent looking seal around it, so I assume the original pipe is still live with gas around the outside of the new smaller yellow pipe.

That would make sense as they lined past our house and we didn't get any interruption (we'd have known as I think the regs state they have to access each house to check incase an open flue boiler or similar doesn't reignite).

After they lined this section we were told we'd have an interruption whilst they replaced our pipe under the garden and connected it to the new main. It turned out we already had a plastic main so they didn't need to work on an our property at all.

They did excavate over every T in the street.

We’ve just patiently watched the electric supply be replaced down our road and connecting lane. 8 weeks to do 600metres…. There’s a lot of things hiding underground in a 1970’s estate built on an old railway line and sidings. It’s slow.

You’re right, it’s still ongoing around the corner 4 months later. Our street is finished though.

So they lined the pipe with no interruption to supply and then there was a day where they turned our section off and connected everyone up. And then filled all the holes back in badly.

I’ve sent SGN an invoice for £100 for my time and materials for correcting their shoddy reinstatement of the grass verge. They’ve acknowledged it and have sent it to another department - I’m not expecting them to pay but you never know 😁

They left it like this with a load of stone / rubble in it and threw some grass seed over it.

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I think I made a better job of it

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We had our gas pipe changed like this last summer, the dug a hole in the verge to access the pipe between our houses, and then another outside the gar cupboard. Then on the day it was to be changed, the gas was off for a couple of hours & they connected the new pipe, then they came and checked the pressure at the meter. Our's wasn't high enough to supply both houses, so next door had to have another hole cut to feed them directly. I was surprised by the quality of the work done to restore the holes in ours and next door drive, both done with pavers and you wouldn't know they'd been dug up. Even the verge was well restored unlike Phil's

Ours was done a coupe of years back.

Yep they just hammer the new pipe through the old one right upto the meter. Ours needed a couple of kettles of hot water pouring down the hole to soften the pipe and get it round the last bend.

It was switched off to no time at all really.