Jody Posted July 23, 2019 Share Posted July 23, 2019 Hi all, I’ve almost finished practically rebuilding a house (kept just the original outside walls!), but I can’t seem to get a definitive answer on whether I need to bond to earth the copper mains incoming water supply when after the stop cock “everything” is plumbed in plastic. There’s a very interesting thread here and in the published document, but it assumes the incoming mains water is in plastic. No where can I find an answer for my scenario, which I’m very surprised some others haven’t got. If it wasn’t all the way over the other side of the house, I’d just put an earth cable in place just in case when it’s inspected they want one, but I can’t bring myself to waste £30 on a redundant bit of cable. Plus I want it all done perfect! My OCD can’t handle a cable being left there for no reason! My head BTW says it would be totally pointless to bond effectively just the stop cock to earth, but regs don’t always seem to make complete sense! cheers Jody Link to comment Share on other sites More sharing options...
Tennentslager Posted July 23, 2019 Share Posted July 23, 2019 @JSHarris and @ProDave will both say no need as, well, why would you need it? Link to comment Share on other sites More sharing options...
scottishjohn Posted July 24, 2019 Share Posted July 24, 2019 but if bath drain is made from brass --then cannot be be a bad idea to earth it . the wife might want rid of you and throw you an electric fire to cuddle when you are in the bath ? when in doubt earth cannot be wrong you only need a seat belt when you crash ! Link to comment Share on other sites More sharing options...
Jeremy Harris Posted July 24, 2019 Share Posted July 24, 2019 There are two separate issues here, one is main protective bonding plus supplementary bonding and the other is supplementary equipotential bonding. Main protective bonding is still required for all metal service pipes coming into a house, even if some of the piping in the house is plastic. Water (including metallic waste pipes), gas, oil etc, plus lightning conductors and structural steel frames have to be protectively bonded. The minimum size of protective bonding wire has changed over the years, but for a TN-C-S/PME installation (which is what most will have) it is now 10mm² (used to be 6mm²). There is no requirement to protectively bond incoming plastic water or gas pipes. Supplementary bonding is used to bond extraneous exposed conductive parts to the incoming PE (usually when an adequate disconnection time cannot be achieved on test, as a way to ensure touch potentials remain below 50 VAC under earth fault conditions). Supplementary equipotential bonding (i.e. earth bonding by an additional conductor, other than one in the supply cable) is only required for a very few special locations now, like electric showers and electric water heaters (if this is mandated in the MIs). There is no requirement to run equipotential bonding wires to metallic sinks, baths, basins, taps, metallic pipework, boilers, etc. It's worth noting that earthing exposed metal parts that are not associated with the electrical installation may significantly increase the risk of serious electric shock, by providing a highly conductive path to earth that may be easily touched. It definitely is not safer to do as @scottishjohn suggests, best to follow the regulations, which have been amended specifically because this risk was recognised. Link to comment Share on other sites More sharing options...
Carrerahill Posted July 24, 2019 Share Posted July 24, 2019 (edited) 11 hours ago, Jody said: Hi all, I’ve almost finished practically rebuilding a house (kept just the original outside walls!), but I can’t seem to get a definitive answer on whether I need to bond to earth the copper mains incoming water supply when after the stop cock “everything” is plumbed in plastic. There’s a very interesting thread here and in the published document, but it assumes the incoming mains water is in plastic. No where can I find an answer for my scenario, which I’m very surprised some others haven’t got. If it wasn’t all the way over the other side of the house, I’d just put an earth cable in place just in case when it’s inspected they want one, but I can’t bring myself to waste £30 on a redundant bit of cable. Plus I want it all done perfect! My OCD can’t handle a cable being left there for no reason! My head BTW says it would be totally pointless to bond effectively just the stop cock to earth, but regs don’t always seem to make complete sense! cheers Jody BS7671 states that as near as possible to the entry point you should protectively bond metallic pipework or services - part of the protection is about what may come in from external sources. What is your water pipe made of as it enters the property? The gas will certainly be metallic so the answer to your question is probably yes to water and for sure to gas. I say probably yes to water because if you have an MDPE pipe in, a metal valve and a PVC pipe out, there really is no point - and the regs do say "metallic". Edited July 24, 2019 by Carrerahill Link to comment Share on other sites More sharing options...
ProDave Posted July 24, 2019 Share Posted July 24, 2019 I am old enough to remember when regs did demand you earthed a kitchen sink and a metal bath. Not any more. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted July 24, 2019 Share Posted July 24, 2019 8 minutes ago, ProDave said: I am old enough to remember when regs did demand you earthed a kitchen sink and a metal bath. Not any more. Not that long ago, either. Our old house was built in 1981 and everything was equipotential bonded. TBH, I'm not convinced that it was ever a good idea, even in the days when the majority of houses didn't have RCD protection. Thinking about it logically, providing a highly conductive touch path to earth is pretty daft. Arguably, chucking an electric fire into a non-earthed bath with someone in it probably wouldn't result in them getting an electric shock, whereas if the bath was metallic and earthed they almost certainly would. Link to comment Share on other sites More sharing options...
Carrerahill Posted July 24, 2019 Share Posted July 24, 2019 (edited) 4 minutes ago, JSHarris said: Not that long ago, either. Our old house was built in 1981 and everything was equipotential bonded. TBH, I'm not convinced that it was ever a good idea, even in the days when the majority of houses didn't have RCD protection. Thinking about it logically, providing a highly conductive touch path to earth is pretty daft. Arguably, chucking an electric fire into a non-earthed bath with someone in it probably wouldn't result in them getting an electric shock, whereas if the bath was metallic and earthed they almost certainly would. No it didn't really make any sense. It is like wearing some heavy rubber boots to do electrical work then putting an earth bond down the side. I don't really get too carried away with earthing things in my house. I let the electrical system take care of it all and don't fuss with pipes and whatnot. Edited July 24, 2019 by Carrerahill Link to comment Share on other sites More sharing options...
dpmiller Posted July 24, 2019 Share Posted July 24, 2019 Oddly, the NIE bod that put our supply on stated that they still require a bond put on at the CW stopcock regardless of the now-in-force regs and plastic pipework. Link to comment Share on other sites More sharing options...
Jody Posted July 24, 2019 Author Share Posted July 24, 2019 Thanks for quick response guys, with I’d found this forum when I started this big renovation project. The soil pipe and all waste pipes are plastic, so no worries about potentially having earth bonded things like the bath. Got no electric heaters or showers either. So not putting in any supplementary bonding. The gas main into the meter box is the new plastic type, but from meter onwards into/throughout the house is all copper obviously, so I’ve put in a 10mm2 earth bond to the gas meter box. The water mains, I was a bit surprised to find is a 15mm copper incoming mains - as at some point in the “recent” past a water meter has been fitted just outside where the mains water comes into the house, so thought they’d have put in a new plastic pipe feed into the house at the same time. So to be 100% accurate; I’ve got about 100mm of water mains 15mm copper sticking out the floor. A brass stopcock then fitted, which I’m going to replace with a new one. Then about another 100mm of copper before it switches to plastic for the rest of the install. (Obviously when the boiler is fitted, it’s normally necessary to have short lengths of copper actually joined to the boiler connections, but if less than 500mm no supplementary bonding required). I could ensure that the only copper bit of the incoming main is the first 100mm which is underneath the kitchen cupboard, so only accessible by removing the plinth etc. Could go straight to plastic after this 100mm. Would that ensure I don’t need (10mm2) main protective bonding to it?? Its a TN-CS system btw. cheers Jody Link to comment Share on other sites More sharing options...
Jeremy Harris Posted July 24, 2019 Share Posted July 24, 2019 You must have a 10mm² main protective bond from the incoming copper water main back to the main earth block where the PEN is connected. There is no need to equipotential bond extraneous metal, like taps, sinks baths etc, and it's safer not to have them bonded. This is the relevant section from the current (18th Ed) OSG for reference (excerpt posted here under the "fair use" provision): Link to comment Share on other sites More sharing options...
scottishjohn Posted July 24, 2019 Share Posted July 24, 2019 1 hour ago, JSHarris said: It's worth noting that earthing exposed metal parts that are not associated with the electrical installation may significantly increase the risk of serious electric shock, by providing a highly conductive path to earth that may be easily touched. It definitely is not safer to do as @scottishjohn suggests, best to follow the regulations, which have been amended specifically because this risk was recognised. we are going to have to disagree on the interpretation of the rules -I do not believe it was altered because of a risk If it did increase the risk ,then they would BAN extra earthing ! -where as they have said its not required for some cases and yet for others still want it that is not the same as your interpretation of an extra risk by having extra bonding . I will take my chance and bond everything as we have done in the past Link to comment Share on other sites More sharing options...
Jeremy Harris Posted July 24, 2019 Share Posted July 24, 2019 1 minute ago, scottishjohn said: we are going to have to disagree on the interpretation of the rules -I do not believe it was altered because of a risk If it did increase the risk ,then they would BAN extra earthing ! -where as they have said its not required for some cases and yet for others still want it that is not the same as your interpretation of an extra risk by having extra bonding . I will take my chance and bond everything as we have done in the past As a former IEE member for many years (what is now IET) I can say categorically that you are wrong. The reason why earthed, non-electrical, metal items pose a risk is simply because they offer zero protection to the electrical installation, and at the same time pose an additional risk to anyone who may be in contact with a faulty electrical appliance and who happens to also touch the earthed exposed metal. Perhaps you'd like to explain why you believe that BS7671 is wrong, and your rationale for suggesting that extraneous metal items benefit from being earthed. Link to comment Share on other sites More sharing options...
Jody Posted July 24, 2019 Author Share Posted July 24, 2019 Thanks, so reading the sentence in the regs....attached If it has an insulated section at point of entry it doesn’t need to be connected to the main earthing terminal. ive attaches a photo I’ve just taken of it currently. if I connect a plastic push fit connector onto the bit of copper coming out of the ground, the max copper on show from the concrete would be 10-15mm, then use plastic from there on. Would that then satisfy the regs to not need earth bonding on it!? Thanks guys Link to comment Share on other sites More sharing options...
Jeremy Harris Posted July 24, 2019 Share Posted July 24, 2019 As that has a metal pipe coming out of the ground to a metal stop cock, I'd bond and tag it. The idea behind main protective bonding isn't primarily to ensure that all metal pipes in the house are at earth potential, it's to both lower Ze (the external earth loop impedance) and to provide an additional path to earth for the CPC for the whole installation if, for any reason, the PE connection at the incomer fails or has a high resistance. This bit dates back to the time when incoming metal water pipes were often used as the primary protective earth for the whole installation, something that's not permitted now, but used to be commonplace years ago. Nothing wrong with this as a means of earthing the installation, either, the main reason it was discontinued as normal practice was the introduction of alkathene pipe around 40 years or so ago, as there was no longer a guarantee that the incoming metal pipe to the house had good connectivity to the ground outside, as there could be a length of plastic pipe just outside the wall. Link to comment Share on other sites More sharing options...
PeterW Posted July 24, 2019 Share Posted July 24, 2019 44 minutes ago, Jody said: if I connect a plastic push fit connector onto the bit of copper coming out of the ground, the max copper on show from the concrete would be 10-15mm, then use plastic from there on. Don't do it... I would leave that stopcock alone, and then clean off the pipe above it with some fine emery paper and add in a full bore lever ball valve. Use that as your isolator, and leave the existing well alone. 3 Link to comment Share on other sites More sharing options...
scottishjohn Posted July 24, 2019 Share Posted July 24, 2019 (edited) I would be more worried about the copper pipe which appears to be set in cement corrosion ? and where does that copper pipe connect to under ground?--one presumes its not to a lead main --so its probably to a plastic one with a compression fitting ? maybe time to make it all plastic underground to above ground . I would , while you are at it --and stop old age problems later with the supply Edited July 24, 2019 by scottishjohn 1 Link to comment Share on other sites More sharing options...
Jody Posted July 24, 2019 Author Share Posted July 24, 2019 Thanks all. Ive threaded through some earth cable today before I fixed the plasterboard up. There’s not much copper pipe to play with before the old stop cock, but it’s leaking very slightly so need to replace it really. Hadn't crossed my mind about the incoming copper pipe being encased in concrete.... It was already in concrete, I then had to screed/level up the floor, so I put the cut off of soil pipe around it that’s in the photo before I poured the floor level around it. I wonder if I should carefully excavate some of the concrete around the incoming copper pipe and see if it is actually within a bit of ducting lower down or even converts from plastic.... Link to comment Share on other sites More sharing options...
Gone West Posted July 25, 2019 Share Posted July 25, 2019 14 hours ago, Jody said: I wonder if I should carefully excavate some of the concrete around the incoming copper pipe and see if it is actually within a bit of ducting lower down or even converts from plastic.... I would, but then I like things done properly . 1 Link to comment Share on other sites More sharing options...
joe90 Posted July 25, 2019 Share Posted July 25, 2019 Be a shame to have to dig it up after you have finished, best do it now I reckon. Link to comment Share on other sites More sharing options...
scottishjohn Posted July 25, 2019 Share Posted July 25, 2019 (edited) I had same situation when i was renovating my kitchen 22mm copper comes out of floor to stop tap behind sink I had already found the main feed before it goes under slab was poly, it was by the side where i dug my pond I suspect it was the builders temp water supply for house as it did not come in a direct line from the main "Toby " I could move the copper pipe around like it was moving on the compression fitting in the floor--so I did not like digging up concrete floor to find where it was loose--so ran new pipe I was lucky enough to be able to run a complete new one from toby into house through garage . the thought of laying a tile floor in kitchen then a year later it all leaks -- no ,no ,no, had to move it Edited July 25, 2019 by scottishjohn 1 Link to comment Share on other sites More sharing options...
lizzie Posted July 25, 2019 Share Posted July 25, 2019 After seeing this topic I checked mine. No earth bonding under stainless steel kitchen or utility room sinks but I do have a big earth bond cable on the incoming main and gas pipe in the plant room. They are metal pipes. My water that runs around the house is all plastic with copper at the last part where it joins into taps etc. Building inspector passed it all so I am presuming it is ok............. Link to comment Share on other sites More sharing options...
Onoff Posted July 25, 2019 Share Posted July 25, 2019 Playing Devil's advocate. There's an outside chance an incoming metallic service could be made live by an external influence so I'd bond the short copper bit that comes in. Link to comment Share on other sites More sharing options...
Jody Posted July 26, 2019 Author Share Posted July 26, 2019 I am going to dig it up around the incoming pipe, I can’t leave it like that without knowing!! Going on holiday now so will let you all know what discoveries I make on my return... I don’t suppose anyone knows of someone in/near Milton Keynes that will sign off my electrical work? I have a second hand tester and have already checked the initial (non live) continuity and insulation tests are ok before I plasterboarded. Link to comment Share on other sites More sharing options...
Jody Posted August 8, 2019 Author Share Posted August 8, 2019 Today’s update now I’m back from holiday! I have excavated around the incoming mains in the house, gone down about 6 inches and it’s still just 15mm copper in the concrete.... Decided to dig up next to the water meter... check out the photos of what I found in there!!!!! 2 blue pipes and one large reddish clay type pipe - no idea what this is!!!! I just cut/dug a hole on the side of the water meter inline with where it is in the house, hoping that’s where the feed is to the house. Trying to avoid digging up too much concrete around the meter! So. I’m assuming 1 blue pipe is mains to the meter and the other blue pipe is the feed to the house..... I think I’m going to have to cut and dig out a bigger area in the kitchen so that I can get down even deeper to the pipe - it “must” change from blue plastic to the copper there surely! Regarding the meter and blue pipes, short of digging up all around the meter. Does anyone know which side of the meter is the input and which is the output - is this standard? I would guess that the input goes to the valve side of the meter base, the output goes from the meter dial side. In which case I think I can assume the blue pipe I can see connecting in by the meter dial is indeed the feed to the house. Link to comment Share on other sites More sharing options...
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