My kitchen refit has prompted me to look at water pipe runs. I was going to optimise the current layout and this led me to digging out around the mains water service pipe, where there is a T-junction. Both branches serve the house (front and back) and are not connected to neighbours. My plans include removing one of the branches, which is badly routed through the house and lies smack next to CH pipes, and we can do without it.

Unfortunately the underground runs are lead pipe, although I did suspect this, as the house was built circa 1900. My water services company will swap these for poly pipe at no cost, so long as customer digs trenches.

Currently, the electrical earthing is connected to these pipes. If the lead is removed, what becomes the new earth?

When I get a confirmed date back from Severn Trent Water for the job, I shall make plans for digging the trenches. Has anyone here done this work before and can share any tips or advice? No doubt it will be a hard slog.

Had a chat with a few neighbours, who were curious when seeing me digging. Neither of them had much idea about it, which led me to wonder just how many old houses are still running on lead pipe (in the section between the main service pipe to the road, and the inlet to the house). Quite a lot I'd imagine.

The health issues are quite scary, but I also read that in hard water areas limescale builds up on the inside of the pipe to form a seal. How effective this is medium to long term though I dont know. Anyway, for peace of mind I want it changed, especially as we have a 3 year old in the house, as kids are more susceptible to the effects of lead poisoning.

I only wish I tackled this 6 years ago before I had the driveway block paved. At least the blocks will come up and go back down easy enough.

Pictures attached...

I'd get an electrician in to check out the elctrical connection to that pipe - if it is indeed earthing you are likley to need an new RCD and electrode. If however, it is equipotential bonding and the pipes change to plastic then there's no risk - you don't need that connection.

Get this wrong and lead poisoning will be the least of your worries

As I mentioned in another thread - all this elctrical work you are undertaking in a kitchen is notifiable to building control under Part P - have you, or do you have a competent contractor available to you that will self certify

Regards

Barney

OK - makes sense on the Part P issue.

It was common practice a while back to rely on a metallic water pipe for safety earthing. Equally metallic services entering the house require equipotential bonding (Gas, water etc). If you change the pipe for plastic the bonding issue goes away (the service cannot introduce an "earthy" potential) - but equally you may lose the means of safety earthing.

Wisest to get it checked - worst case would a be a front end RCD and electrode (or connection to a suppliers earth depending on what service the supplier presents) - either way probably not a bank breaker

Regards

Barney

If they replace the lead pipe with mdpe

The earth connection should be after your stopcock but no more than 600mm after the stopcock.

I assume you habe copper pipe, so just get a tenby earth clamp and connect away.

Tony

When I replaced my parents incoming lead pipe we consulted an electrician and he called the electricity board who connected the earth to the incoming neutral. I thought this very strange but it was done by the electricity board!!!! I cant remember if they charged for this, but I amn sure they would not do iy for nothing!!!

@John Just remember to retain all the old lead piping and take it to the scrappy for some beer money thats what the what the water contractor will do and you might as well make some cash.

Well, having a detailed drawing of the DNO service won't help you if you get a bit over zealous sticking an illegal 951 clamp on a paper insulated lead coated service cable - it will be dramatic, trust me. Even DNO's now use constant pressure spring connectors because of the risk.

In terms of earthing and bonding perhaps the easiest way to think of it is that earthing provides a low resistance path for high current faults that ensure rapid opening of fuses or circuit breakers - ie it makes protection operate quickly - bonding simply limits touch voltages bewteen metallic parts whilst that protection is operating.

Regards

Barney

OK - if you have a PME earthing system, what you are looking at on the lead pipe is equipotential bonding. The new plastic service coming in won't need bonding but in all probability any copper inside the building will - reconnect to the metal pipework via a BS 951 clamp

If you have plastic plumbing internally then the bond is redundant. just leave it coiled at the stopcock location

trust that helps

Regards

Barney

No worries.

If it's predominantly copper then connect with a 951 clamp just after the stopcock. You don't really need to bridge out short plastic sections as the remaining metal bits aren't likley to introduce any potentials that aren't already there (They have effectively been isolated by virtue of the plastic incomer and random plastic inserts)

Regards

Barney

Pure water is a pretty poor conductor of electricity, so depending on where you live and what the water is like you could have virtual isolation through a water filled plastic pipe.

Water is only an effective conductor of electricity when something is dissolved in it, like salt or any number of other impurities.

<blockquote><cite>Posted By: barney</cite>

This business of bonding and plastic pipes has always bothered me and several electricians have failed to give concise information. One thing that no-one seems to mention is that the water in the pipe should give continuity

Apply a bit of ohms law to the water as a resistor and you should see that what you think is a risk isn't really credible.

</blockquote>

A bit of Ohm's Law applied to water:

Assume non-conducting pipe is 12mm bore and 5 metres long.

Resisivity of pure water is around 1.8 x 10^5 ohm metres at 20 deg C

The resistance of a 5m length of pipe of 12mm diameter bore filled with pure water will be around 8000 Mohms

With the full mains potential of 240V across it the current it would pass would be just 0.003 microamps

The lowest current that we can normally start to feel if we touch a couple of conductors is around 1mA, or around around 300,000 times greater than the current that could flow through the water in this pipe.

If the water had impurities that made it more conductive, then the current would be higher. For example, if it were the worst case (I'll use seawater as this) then the resistance in the same column of water would reduce to about 880kohms and the current from an applied potential of 240V would increase to about 270 microamps, still only about 1/4 of the current needed for us to detect it and well below the threshold that would trip the most sensitive earth leakage detector.

Both these examples show that the water is very poor at providing continuity through a plastic pipe.

Yes, i do believe i said it was a main bond several posts ago.

Got a feeling that if you have 190mm of plastic that is enough for an electrical break as far as the water conductivity is concerned, copper pipework is another matter.

<blockquote><cite>Posted By: barney</cite>You are confused - I didn't say that - Joe90 did.</blockquote>


Sorry, I'm still confused. It was your post I was quoting from, not someone elses, this one, last sentence, third paragraph:

<blockquote><cite>Posted By: barney</cite>P.S. it looks from your photo that the earth is conected to the nuetral.

It would be - it's Protective Multiple Earthing. The neutral and earth are combined in the suppliers cable (a PEN conductor) and then earthed at multiple locations - that's why bonding is so important because if the neutral opens up (bob the builder and his JCB for example), you lose the earthing and everything starts rising towards mains voltage - if it's bonded it's all at the same potential and you will only receive a very mild shock - if it's not bonded (and it's earthy) then you will get a hell of a belt.

This business of bonding and plastic pipes has always bothered me and several electricians have failed to give concise information. One thing that no-one seems to mention is that the water in the pipe should give continuity

Apply a bit of ohms law to the water as a resistor and you should see that what you think is a risk isn't really credible.

The purpose of bonding is to connect conductive parts that are at or around earth potential and enter the property to the main earthing terminal to create an equipotential zone - with that in mind, you should see that earthing bits of isolated copper pipe that are already within the zone is totally pointless.

Regards

Barney</blockquote>

I wholeheartedly agree that the resistance of the water column in a reasonable length of plastic pipe would be such as to limit the current to such a low value that you'd probably not even feel a shock, should you be unfortunate enough to try and ground yourself to it whilst holding on to a live connection somewhere, which is, I think, the point we're both agreed on.

OK, I think I see what happened. I couldn't see a difference between the stuff you'd typed and the stuff that you had cut and pasted from the post by Joe90, as there weren't any tags around the quoted section to show who'd written it, like this:

<blockquote><cite>Posted By: joe90</cite>This business of bonding and plastic pipes has always bothered me and several electricians have failed to give concise information. One thing that no-one seems to mention is that the water in the pipe should give continuity?</blockquote>