Green Building Forum - Removing lead pipes

Removing lead pipes

jonharris — Sun, 21 Aug 2011 12:53:07 +0100

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...

Removing lead pipes

jonharris — Sun, 21 Aug 2011 12:53:47 +0100

Removing lead pipes

barney — Sun, 21 Aug 2011 13:25:38 +0100

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

Removing lead pipes

jonharris — Sun, 21 Aug 2011 15:27:38 +0100

Thanks Barney.

House looks to be equipotential bonded - earth wires exist to connect all copper pipes. The kitchen ceiling is off and the bathroom is above it, so I can see all the plumbing connections. There is only a small amount of plastic piping.

Building inspector advised that as I'm only putting back existing electrical fittings and not extending it then certification is not required.

Either way, I'll probably get a sparky in to look at the earthing issue.

Removing lead pipes

barney — Sun, 21 Aug 2011 15:46:50 +0100

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

Removing lead pipes

SteamyTea — Sun, 21 Aug 2011 18:24:11 +0100

An earth rod would sort it, or you can join it to the incoming electrical sheathing.

Removing lead pipes

Tonyt — Sun, 21 Aug 2011 22:03:06 +0100

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

Removing lead pipes

barney — Mon, 22 Aug 2011 11:15:47 +0100

An earth rod would sort it, or you can join it to the incoming electrical sheathing.

I wouldn't recommend the latter as a diy job. Most service cables (ie the bit from the distributor to the house) are protected from short circuit by the distributor fuse - which will be pretty big. Hence, most service cables are "sacrificial "in part - they will burn back for a long time. Bear in mind that under the lead sheath is paper insulation - if you cause enough compression it can be more than a little dramatic - and is also illegal.

Equally, the former would also need an RCD (a minimum of one but ideally more)

As I suggsted - you need to ascertain if it is in fact earthing or bonding before you mess around with it.

Regards

Barney

Removing lead pipes

joe90 — Mon, 22 Aug 2011 15:27:53 +0100

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!!!

Removing lead pipes

barney — Mon, 22 Aug 2011 18:44:32 +0100

connected the earth to the incoming neutral. I thought this very strange but it was done by the electricity board!!!!

Perfectly normal on the suppliers side - the neutral is always secured to earth at substations etc, not always so at the consumers end - that depends on the particular supply type being offered

Regards

Barney

Removing lead pipes

tiimjp1 — Mon, 22 Aug 2011 18:51:21 +0100

@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.

Removing lead pipes

SteamyTea — Tue, 23 Aug 2011 07:49:37 +0100

Posted By: barneyI wouldn't recommend the latter as a diy job

Nor would I especially as these days we are meant to have detailed drawings of electrical installations.
Good comment about Earthing and Bonding, they are different and serve a different purpose.

Removing lead pipes

barney — Tue, 23 Aug 2011 08:49:42 +0100

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

Removing lead pipes

jonharris — Wed, 24 Aug 2011 14:21:01 +0100

Thanks for the replies everyone.

Here is a photo of inside the meter box. It looks like it's earthing here too. A sticker on the CU clearly states it uses a 'protective multiple earth system'. Does this shed any more light on things?

tiimjp1 - yes the lead will be going up the scrap yard. Dont know what current rates are but I reckon there's about 20-25m of it, so enough for a few beers hopefully!

Removing lead pipes

barney — Wed, 24 Aug 2011 14:25:47 +0100

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

Removing lead pipes

jonharris — Wed, 24 Aug 2011 14:35:12 +0100

Brilliant Barney - thanks very much. It's mostly copper inside the building with just a couple of plastic sections of pipe. I think I read elsewhere that the copper both sides of a plastic section needs to be bridged with earth cable/clamps too?

Removing lead pipes

barney — Wed, 24 Aug 2011 14:55:21 +0100

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

Removing lead pipes

joe90 — Wed, 24 Aug 2011 15:34:29 +0100

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?

P.S. it looks from your photo that the earth is conected to the nuetral.

Removing lead pipes

JSHarris — Wed, 24 Aug 2011 15:39:47 +0100

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.

Removing lead pipes

barney — Wed, 24 Aug 2011 18:10:24 +0100

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

Removing lead pipes

JSHarris — Wed, 24 Aug 2011 18:34:31 +0100

Posted By: barney

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.

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.

Removing lead pipes

barney — Wed, 24 Aug 2011 19:44:25 +0100

Indeed - that's why I suggested the risk isn't credible so theres no point festooning the CWS pipes with loads of bonding clamps and straps - particularly if the incoming is also plastic

Regards

Barney

Removing lead pipes

Tonyt — Wed, 24 Aug 2011 21:21:41 +0100

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

Removing lead pipes

JSHarris — Wed, 24 Aug 2011 21:50:41 +0100

Posted By: barneyIndeed - that's why I suggested the risk isn't credible so theres no point festooning the CWS pipes with loads of bonding clamps and straps - particularly if the incoming is also plastic

Regards

Barney

Sorry, I must be a bit confused. I thought that your view was, quote: "One thing that no-one seems to mention is that the water in the pipe should give continuity", yet the resistivity of water is such as to allow a potential of hundreds of volts to exist between opposite ends of a 5m length of plastic pipe filled with water before reaching an RCD threshold, which suggests that water is very poor at providing continuity.

Whether this is important I'm not sure, but it does mean, for example, that a faulty electric water heater (say, an under-sink instantaneous type) plumbed in from the mains with plastic, but plumbed to the outlet with copper, that develops a faulty earth, could raise the potential of a tap to a lethal voltage.

If all the pipework is bonded to earth, then this problem doesn't arise, as the RCD will trip due to the fault.

Maybe I'm just being a bit overly sensitive about safety and this is a highly improbable sequence of events, but I did have an immersion heater once that developed a fault like this (a leak to earth due to corrosion).

Removing lead pipes

SteamyTea — Wed, 24 Aug 2011 22:35:38 +0100

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.

Removing lead pipes

barney — Wed, 24 Aug 2011 23:21:00 +0100

Sorry, I must be a bit confused. I thought that your view was, quote: "One thing that no-one seems to mention is that the water in the pipe should give continuity",

You are confused - I didn't say that - Joe90 did.

Whether this is important I'm not sure, but it does mean, for example, that a faulty electric water heater (say, an under-sink instantaneous type) plumbed in from the mains with plastic, but plumbed to the outlet with copper, that develops a faulty earth, could raise the potential of a tap to a lethal voltage.

Only if there has been a failure of both basic insulation and means of earthing - lets not confuse earthing of exposed conductive parts and bonding of extraneous conductive parts. And assuming both of those, a lethal voltage with respect to what - you would also need an "earthy" point to touch at the same time.

If all the pipework is bonded to earth, then this problem doesn't arise, as the RCD will trip due to the fault.

Indeed - but again you are using earthing of extraneous metalwork to compensate for a two concurrent faults in an appliance.

Maybe I'm just being a bit overly sensitive about safety and this is a highly improbable sequence of events, but I did have an immersion heater once that developed a fault like this (a leak to earth due to corrosion).

Failure of your protection then - any fault to earth should operate the circuit protection PDQ.

I think the point I was making was that you cannot receive a touch voltage shock of any magnitude off a piece of copper pipe that is effectively isolated from earth by a chunk of plastic pipe - as a general guide any metalwork presenting more than about 23kOhms to the main earthing terminal could only allow about a 10mA shock current to flow - so perfectly safe for most people - why would you want to make it more dangerous by "earthing" it

regards

Barney

Removing lead pipes

JSHarris — Thu, 25 Aug 2011 08:37:49 +0100

Posted By: barneyYou are confused - I didn't say that - Joe90 did.

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

Posted By: barneyP.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

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.

Removing lead pipes

barney — Thu, 25 Aug 2011 08:48:13 +0100

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

Sorry, I must be a bit confused. I thought that your view was, quote: "One thing that no-one seems to mention is that the water in the pipe should give continuity",

Nope that was Joe90 - I was quoting him (badly)

regards

Barney

Removing lead pipes

JSHarris — Thu, 25 Aug 2011 09:42:27 +0100

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:

Posted By: joe90This 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?

Removing lead pipes

Joiner — Thu, 25 Aug 2011 10:06:03 +0100

"Cutting and pasting to give a more conventional look to a post is probably best done with the addition of the things at either end of this."

"And a quote within a quote can be designated 'thus'."

No one falls out then. Hopefully.