Earthing the water supply

[French Chris]

Hello all. I'm hoping to pick your collective brains on this subject.

We moved house 12 months ago and I am gradually checking out the plumbing and wiring etc.... I want to understand exactly what I have got and what I am missing in case we do any future work on the house - it's a 1960's bungalow by the way.

I can't see any earth bonding in he house at all with regards to stopcocks, nor any supplementary bonding anywhere (yikes!)

There are 3 seperate stopcocks in the property bringing mains water from outside (yes, Three!). One is in the attached garage and is just for outside taps etc. One is in the bathroom as the principal stopcock and the 3Rd is under the kitchen sink. They are all old and copper. 90% of our pipework around the house is sill copper, but with some plastic for more recent renovations (before my ownership). There is also a gas meter in the garage but that doesn't seem to have any earth bonding either.

I assume that I need a 10mm bonding earth cable from each stopcock back to the consumer unit.

To keep things tidy, I can run a cable up through the loft and drop it's where needed, but do I need 3 seperate cables running from the CU or can it be one cable that is then spurred via a junction box or some such method?

Forthe supplementary bonding, I assume it's ok to use 4mm earth and clamp between pipes etc.

Finally, the electric shower will need cross bonding. Does this require a 2nd earth cable from the shower unit itself or can it be run from the 60amp fusedvswitch outside the bathroom?

Some of this I may do myself, but I will get quotes for some of the work too. I just wanted to understand my best options before a local electrician tries to dupe me into paying too much or not let me make it as neat and tidy as possible!

Look'g forwards to all your help and suggestions. PS: moving house is not an acceptable suggestion!

Many thanks,

Chris

 

[CBW]

Regards cross bonding, I believe this depends on which edition your CU is wired to. As for the Gas and water, it might be that the incoming supplies are ran as far as practicable in pvc, therefore negating the need for such bonding. Have you gathered this information yet?

 

[EFLImpudence]

On a general note:

Stopcocks are irrelevant and have no bearing on whether bonding is required or not.

What is "cross-bonding"?

 

[French Chris]

Hi EFL,

I understood that water supply pipes entering the house should be earth bonded within 600mm of the stopcock. This would mean 3 seperate cables from different parts of the house to the CU unless they can be joined together in the loft with only a single cable going down to the CU.

 

[CBW]

What is "cross-bonding"?

It is installed across metallic pipes I believe, such as say a Combi boiler which has 5 copper pipes generally at the boiler, cross bonding would link these together.

 

[EFLImpudence]

I understood that water supply pipes entering the house should be earth bonded within 600mm of the stopcock.

No, if they are extraneous-conductive-parts, pipes should be bonded "at the point of entry where practicable".

This would mean 3 seperate cables from different parts of the house to the CU unless they can be joined together in the loft with only a single cable going down to the CU.

Well, it might but presumably all the pipes are joined and run from the main supply to the house.

They may be joined by any suitable connector and run to the Main Earthing Terminal which might be in the CU.

 

[EFLImpudence]

It is installed across metallic pipes I believe, such as say a Combi boiler which has 5 copper pipes generally at the boiler, cross bonding would link these together.

A plumbers' fantasy which has never been required.

 

[French Chris]

Ok, so I guess there is only a single mains supply water pipe for the house that runs underground from the water meter in the street. This is then spurred into the 3 stopcocks around the house.
All I can see above ground is copper pipe and I doubt that the underground supply pipe is bonded, so it needs to be done.

Since I cannot tell if any of the underground pipe is plastic, surely the safest thing is to assume that it is, so all three rising mains need bonding at closest point indoors above ground.

So 3 seperate 10mm earth cables joinedin the loft then a single 10mm cable connects them all to the CU. Does this sound reasonable ?

thanks

 

[EFLImpudence]

Ok, so I guess there is only a single mains supply water pipe for the house that runs underground from the water meter in the street. This is then spurred into the 3 stopcocks around the house.

I don't know. Did you not say one of the stopcocks turns off everything?

All I can see above ground is copper pipe and I doubt that the underground supply pipe is bonded, so it needs to be done.

It might. You can't tell by looking at it.

Since I cannot tell if any of the underground pipe is plastic, surely the safest thing is to assume that it is,

Don't you mean assume that it is not?

so all three rising mains need bonding at closest point indoors above ground.

Well, you should not bond parts that are not e-c-ps but if the water and gas pipes are joined to the earthing system of the house by appliance CPCs(earth wires) then unnecessary bonding will not introduce a hazard.

So 3 seperate 10mm earth cables joinedin the loft then a single 10mm cable connects them all to the CU. Does this sound reasonable ?

Yes - but as I said - to the MET which might not be in the CU but a block near the incoming supply.

As for the Supplementary Bonding - if you have Residual Current Devices on all the circuits of the bathroom; and a couple of other satisfied conditions; then SB is not required.