Equipotential bonding of redundant gas pipes

Would you need to get the earthing checked to make sure no part of your electrical system is relying on the gas pipe for its earth?

It would be crazy if it was as it’s all plastic underground.

Tim

Was it when the wiring was first installed? When I lived in my previous flat, the distribution network operator replaced the supply cables for all the flats. One of the guys told me a surprising number of flats did not have a functioning earth.

Not everywhere. We had a steel gas service pipe replaced with yellow plastic (fed through the rusty steel pipe) only this year. John

Of course not. *My* gas supply comes through plastic pipes though (apart from the last metre to the meter).

Tim

Wouldn't that "last metre" be just as effective as a 1 metre long ground spike?

All by the by though as my earth is provided by my DNO.

Tim

My mother's house had the gas pipe replaced with yellow plastic this summer. All houses in the estate had new pipes to the house after the mains gas pipe in the road was replaced/reconditioned. The old pipe was iron(?). House was built in the 1960s.

Did they check that any remaining internal metal pipes were bonded?

Are you removing all the pipework inside the house? ie there will be no exposed metalwork indoors once this is done? Or at least no conductive path from something buried in the ground to exposed metalwork?

In which case you've removed the extraneous conductive parts and this bond is no longer necessary.

It is worth checking your main earthing terminal is connected where the electricity supply comes in, just to be sure somebody hasn't done anything stupid and this is your one remaining earth, but if your installation is relatively modern I wouldn't have expected that.

Theo

A qualified "yes"...

If the internal gas pipework in the house will remain as an extraneous conductive part[1], then it will need to be included in the main equipotential bonding *somewhere*, it does not need to be outside with a fugly fly lead. Also note that the fly lead in the picture does not in itself include the pipe in the house's EQ zone - it just connects the pipe to some version of local earth (which may or may not be the earth that the house is connected to depending on the earthing system in use for its electrical installation[2]

Before you remove the link wire, make sure that the gas pipe was not the only earthing connection in a TT Earthed[2] installation (my previous house originally had TT earthing that used the gas pipe as the only earth. It also had an old VO ELCB, and no RCDs)

If you have TT earthing and that was the main earth electrode, then you will need to provide a new TT earth to replace it (or upgrade the install to TN-C-S / PME if that is an option).

Our earth is connected to what looks like the sheath of our incoming main.

Yup that looks like a TN-S install. So no need for a local earth rod (or gas pipe) connection.

There is no harm in having the remaining internal pipework connected to the main EQ bond, since it prevents the pipes introducing a potential other than that of the main properties earth into any areas where it might prove unwelcome.

You don't need the external bridge connection since it was not using that pipe as a main earth.

Yes and no - they put a big label on the meter output pipe saying it wasn't bonded and it should be sorted. As far as I'm aware they didn't inform my elderly mother but they may have done but she didn't understand what they were saying.

As I understand it the bonding point should be 300mm (or less) from the meter.

You are not supposed to bond the incoming supply of the gas only the meter side. The only exception is when removing or refitting a meter when a temporary bond is fitted.

Adam

I was wondering how the main gas supply seems to have 'disappeared' inside a new white PVC pipe? Have transco etc been back and capped it off by removing their control valve?

I have a DNO earth. I have just spotted that, when the gas guys moved my meter to suit the new plastic pipe, the disused metal one was capped. They have transferred the earth bond, which had been correctly sited on my side of the meter, onto the stub of supply pipework.

That means that the house gas piping is currently not bonded. Looks like time to reach for the roll of earth cable I have handy. :-(

Chris