Bond sinks and mains water with plastic at start

[Sadsyndrome]

Hi sorry very long one. Please hop to bottom paragraph for short version. I’m just about to refurb bathroom in my 1986 house but bonding always confused me and I am still confused now! So my main incoming water pipe (extraneous) is Currently bonded To MET in 10mm and hot and cold pipes cross bonded near to main bond clamp. My gas pipe is also bonded to MET with 10mm. A stainless steel sink in small utility room is bonded ( I did that over 20 years ago) with the copper pipes as it has with plastic between pipes and sink. The bathroom has a shaver socket and Water based radiator with copper pipes, I see no signs of supplementary bonding.

i think bonding sinks is a very old requirement and I also believe water main with plastic incoming pipe no longer requires bonding.

But if the sink and main water is not bonded and there are plastic pipes section in and around the plumbing system what would happen if a fault condition eg cable touching copper pipe or sink occurred? The house is 1986 and all circuits protected by a single RCD 30ma but if the sink and some of the main Copper pipework is not earthed I guess the rcd wouldn’t detect leakage and would sit at mains voltage? Is that right? Only when someone came along and touched the pipe or sink would rcd hopefully trip (they can go wrong themselves).

I guess what I am asking is there a good reason NOT to have Steel sink and main water incomer bonded to MET? I know it’s not stipulated by regs but in this case I can see a benefit of doing it. Also given the lack of electrical equipment in bathroom and the fact the rcd protects all circuits, is the lack of supplementary bonding there OK?

 

[loz2754]

Extraneous in this context means not part of the electrical installation.

 

[Midwest]

Thanks for that it is one I had seen . It says at 2.00 that any less than 1667ohms no bonding required (assuming rcd 30ma). At the end it says less than .02MOhms you do need to bond and above you don’t? Both say measure Between Known earth in the room and lump of metal you want to know whether to bond or not.

He said that between below 0.02mohms and above 1667ohms, would need bonding. However, bear in mind the accuracy of using IR tester of measuring ohms.

I don’t agree with not testing to discover if something is extraneous or not though. It depends on the property. In my three year old house, all pipework is plastic, except the internal gas, and short pieces of copper to shower valves. So no reason to test. But in older houses, with all copper pipes, with routes unknown unknown, such a test is the only way to confirm IMO.

 

[LastManOnline]

Thanks for clarifying “extraneous” as that was confusing me. Btw Is extraneous in a special location the same or is it extraneous to the location, in my case bathroom?

"extraneous" technically is defined as metalwork that could "introduce a potential" usually earth potential. I have also noticed that some forums have applied it in its dictionary sense of "originating from outside". However electrically speaking metalwork "originating from outside" but that "cannot introduce a potential" is not what is electricians consider as extraneous. You can simplfy the matter for yourself by simply carrying out an IR test on the metalwork in question. Isolated metalwork will likely give either an "infinity" or an extremely high megaohm reading. Metalwork that gives a lower reading (30,000 ohms for instance) though technically "extraneous" is not required to be bonded in UK as that resistance is deemed too high to allow a dangerous shock to occur. I believe the cutoff point in UK to be around 22,000 ohms. I, m sure other posters will confirm

 

[LastManOnline]

"extraneous" technically is defined as metalwork that could "introduce a potential" usually earth potential. I..

Apologies to previous posters. I had, nt read through all the comments and ended up repeating some of what had already been stated.

 

[DPG]

Apologies to previous posters. I had, nt read through all the comments and ended up repeating some of what had already been stated.

Worth repeating. As you say, a lot of people dont understand the while bonding thing.

 

[ipf]

Earthing and Bonding.....here we go. It's a case of having a read and sort out the difference between them. As indicated, find some old threads on the subject.

Back to the 15th..... Earthing? Just bond it....he, he! ?

Remember taking earth wires from the nearest point to bond radiators, for example.

Wrong with this sketch...you'd have to unplug the kettle to reach the tap and refill it, thus eliminating the problem.
It's a guide, by the way, not the actual regs.

 

[Sadsyndrome]

He said that between below 0.02mohms and above 1667ohms, would need bonding. However, bear in mind the accuracy of using IR tester of measuring ohms.

I don’t agree with not testing to discover if something is extraneous or not though. It depends on the property. In my three year old house, all pipework is plastic, except the internal gas, and short pieces of copper to shower valves. So no reason to test. But in older houses, with all copper pipes, with routes unknown unknown, such a test is the only way to confirm IMO.

I would like to test for interest more than anything as I have a 1986 house with copper pipe throughout but with some plastic additions that I have made over the years. However all CH pipes are connected to bonded gas main pipe via boiler and copper hot water tank. Assuming the flexible hoses ( ones with steel braiding) are conductive then the cold water pipes are connected to hot water pipes via those through the mixer taps, apart from útil room where I used plastic flex is for some reason. So electrically the whole copper pipe system will be at same potential (met bonded to gas). That’s without the current bond on the cold water main (no longer required apparently as it is plastic incomer) and the cross bonding between hot and cold that exists under sink in útil room and also by stop cock. Therefore without disconnecting these pipes and “bonds” the test would be pointless as the reading to MET will be very low. Oh and one other point which would make testing difficult, I don’t own a IR or MFT tester? given I have to get someone in to test whatever work is done so I’m not going to fork out for one now As I have to spend that money on a more modern up to date sparks than me shame that I like new toys.