Verifying water bonding

[Dartlec]

Adding a socket in a house where the downstairs bathroom fitters appear to have boxed in the original stopcock and 'moved' it sideways into the garage, but not moved the original bonding cable. It's now firmly inaccessible behind the toilet. The cabling at the consumer unit is also unclear.

Wander lead test to the only clean bit of copper I could find under the sink gives a reading of 0.04 Ohms (With Gas Bonding removed), but given that I can't get at the bonding cable is that considered adequate verification for a certificate?

It's a TN-S system, so thinking about it, it could be picking up continuity to earth from the buried pipe.

The owner was working from home so I couldn't isolate the entire system and disconnect the main earth to retest without. I will be returning for further works so what is the correct procedure to test bonding in an existing situation like this? Test at one point? or any and all accessible pipework?

As a bonus question, how do others deal with situations where a small job is being done that isn't directly related to bathroom or location with pipes and water or gas bonding isn't present - note that on the MWC, or refuse to do the work at all unless it's added?

 

[captaincaveman]

Suggest to the customer to get the bathroom fitters back to make good (at their cost)?

 

[Dartlec]

Suggest to the customer to get the bathroom fitters back to make good (at their cost)?

I believe it was done 5+ years ago now, unfortunately - supposedly had an 'electrician' on their team too...

 

[captaincaveman]

I believe it was done 5+ years ago now, unfortunately - supposedly had an 'electrician' on their team too...

Yeh, I seem to hear that quite often (kitchen fitters too). Never once seen a certificate held by the customer to back that up though

First I'd quickly check the rest of the electrics in the room to ensure the builders "electrician" hasn't made any mistakes that need rectifying (if there are downlighters on connection blocks in tape I'd wager the builders did the electrics). If there are, point out they've messed up and offer to correct the issues - which the customer will probably be grateful for, and get the bonding sorted at the same time. Either way I personally would make the bonding accessible I'm sure any scheme visit or future EICR would insist on it...
Can you easily lay a new bonding or remove a tile etc to access it?
Sometimes bonding is a right royal pain to get to. I've just replaced an external ccu (that's another story involving rain & pain) where I eventually found the water inlet behind the immersion heater, in the centre of an apartment, after emptying all the kitchen cupboards, removing bath panels etc stupidly thinking it might be on an outside wall

 

[James18288]

Can you see the connection behind the toilet? If I could see it, and test to the pipe work as you’ve said, I’d be happy to carry out the minor works you have described. Then advise the customer about the situation, maybe talk to them about an EICR to find any other hidden nasties?

Can you see the cable for the bonding conductor Anywhere near the new stopcock? And if so is there anywhere you could access it? If so, a Possible addition of an earthing terminal and appropriate labels, a new cable and earth clamp Close to the stopcock? Not the prettiest of solutions though!

If not then Rather than taking out tiles cutting access holes etc, would more than likely be easier to get a plumber to fit a short length of plastic pipe as close to the stopcock as possible. Then No need for the main protective bonding.

 

[Ian1981]

Just note it in the comments section and that you have carried out as far as reasonably practicable testing to verify that the water pipe has a relatively low resistance to earth. What else can you do?

 

[Wilko]

Hi - the low Ohms may also come from the boiler circuit or some such. I’ve seen a few where it had been presumed present on historic certs, but in the end it was a 1.5mm conductor that was being measured.

 

[Dartlec]

Hi - the low Ohms may also come from the boiler circuit or some such. I’ve seen a few where it had been presumed present on historic certs, but in the end it was a 1.5mm conductor that was being measured.

I did wonder that - never actually checked to see if a boiler cover is connected to the supply earth, but I'd guess if so that copper pipe connections to it would in theory be bonded then. This wasn't anywhere near the boiler from what I could tell but might have to investigate further on my next visit.
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Just note it in the comments section and that you have carried out as far as reasonably practicable testing to verify that the water pipe has a relatively low resistance to earth. What else can you do?

That's what I did in this case, since the work I was doing was not within reach of any water pipes so I was happy that I wasn't introducing an additional risk - just wondered what the general practise was in such cases....
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Can you see the connection behind the toilet? If I could see it, and test to the pipe work as you’ve said, I’d be happy to carry out the minor works you have described. Then advise the customer about the situation, maybe talk to them about an EICR to find any other hidden nasties?

Can you see the cable for the bonding conductor Anywhere near the new stopcock? And if so is there anywhere you could access it? If so, a Possible addition of an earthing terminal and appropriate labels, a new cable and earth clamp Close to the stopcock? Not the prettiest of solutions though!

If not then Rather than taking out tiles cutting access holes etc, would more than likely be easier to get a plumber to fit a short length of plastic pipe as close to the stopcock as possible. Then No need for the main protective bonding.

Plastic insert may be worth considering - though that only works if the pipe doesn't go back into the ground after that, from what I understand and since it's in the garage I'm not sure I can easily verify that either...

The original stopcock (and possibly cable) is in a boxed in section with the soil pipe with no access panel (of course), beside expensive bathroom cabinetry. Perhaps I should just wait until there is an inevitable leak and follow behind the plumber
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Yeh, I seem to hear that quite often (kitchen fitters too). Never once seen a certificate held by the customer to back that up though

First I'd quickly check the rest of the electrics in the room to ensure the builders "electrician" hasn't made any mistakes that need rectifying (if there are downlighters on connection blocks in tape I'd wager the builders did the electrics). If there are, point out they've messed up and offer to correct the issues - which the customer will probably be grateful for, and get the bonding sorted at the same time. Either way I personally would make the bonding accessible I'm sure any scheme visit or future EICR would insist on it...
Can you easily lay a new bonding or remove a tile etc to access it?
Sometimes bonding is a right royal pain to get to. I've just replaced an external ccu (that's another story involving rain & pain) where I eventually found the water inlet behind the immersion heater, in the centre of an apartment, after emptying all the kitchen cupboards, removing bath panels etc stupidly thinking it might be on an outside wall

There's plenty to pick apart (Emma board, with various contactum and Europa MCBs, and one RCBO for their loft conversion), so I've already told him to budget for a new board sooner rather than later, but he obviously wasn't wanting to do it just to add one twin socket ...

The bathroom electrics weren't the worst I've seen - though i did have to replace a taped connector block on top of the expensive mirror housing while replacing nasty halogen G4 downlights with LED ones...

Running a new bonding cable would be a real PITA though, past stairs and the fully tiled bathroom. Really no access to the area I think it might be in, without damaging fittings - and then if it's not there I've wasted my time or their money...

Been a while since I've had a job without obvious bonding, thankfully....I feel your pain!

 

[Vortigern]

132.16 Additions and alterations to an installation
No addition or alteration, temporary or permanent, shall be made to an existing installation, unless it has been ascertained that the rating and the condition of any existing equipment, including that of the distributor, will be adequate for the altered circumstances. Furthermore, the earthing and bonding arrangements, if necessary for the
protective measure applied for the safety of the addition or alteration, shall be adequate.

First thing I do is confirm earthing system is in place and meets the above before taking on any work. I would say this is the most misunderstood area bonding and supplementary bonding, I personally still don't fully understand it in all its aspects, there are some complex areas.

The cabling at the consumer unit is also unclear

Do you mean no labelling or the bonding cables were not clear? I suppose you could have removed the bonding at the MET and measured from the end of it to the local pipe to confirm the actual connection. Can you see the bonding cable at or near where it is allegedly clamped?

 

[nicebutdim]

First thing I do is confirm earthing system is in place and meets the above before taking on any work. I would say this is the most misunderstood area bonding and supplementary bonding, I personally still don't fully understand it in all its aspects, there are some complex areas.

I can not tell you how much it means to read these words

It is one subject that I've read about repeatedly and every time I get it half way straight in my head, some other consideration raises new doubts.

 

[Dartlec]

132.16 Additions and alterations to an installation
No addition or alteration, temporary or permanent, shall be made to an existing installation, unless it has been ascertained that the rating and the condition of any existing equipment, including that of the distributor, will be adequate for the altered circumstances. Furthermore, the earthing and bonding arrangements, if necessary for the
protective measure applied for the safety of the addition or alteration, shall be adequate.

In a situation where the addition does not affect any area where any water pipes are present, let alone accessible, would the bonding arrangements be necessary to ensure ADS for the alteration to comply with that regulation? I don't know what an expert view would be on that and I am by no means an expert.

First thing I do is confirm earthing system is in place and meets the above before taking on any work. I would say this is the most misunderstood area bonding and supplementary bonding, I personally still don't fully understand it in all its aspects, there are some complex areas.

Do you mean no labelling or the bonding cables were not clear? I suppose you could have removed the bonding at the MET and measured from the end of it to the local pipe to confirm the actual connection. Can you see the bonding cable at or near where it is allegedly clamped?

I usually check bonding as a matter of course and it has been a good while since I've seen one not connected to water pipes.

In this particular situation, the gas bonding was connected to a separate earth bar with the main TNS earth and the meter was in the same cupboard, though I did have to move it to the correct side of the meter and actually tighten the clamp.

The possible water bond cable was in the consumer unit and not labelled or terminated in a way that could be identified. It could also not be disconnected safely (in my view) as the client was working from home and I was unable to isolate the entire consumer unit to get safe access to it.

I therefore carried out a test with gas bonding disconnected, but not the main earth - and got 0.04 Ohms to the copper pipework under the sink.

As already mentioned, that may possibly have been from the boiler earth, although the boiler was not that close. I think that if it were continuity from the copper pipe to tje ground itself and then back via the TN-S sheath, the reading would be significantly higher?

I will be returning to carry out other work so will be investigating further, but the situation got my brain thinking, hence the question.

In a situation where the cable cannot be visually seen at all, in what circumstances, if any, is it acceptable to verify bonding to water via testing alone?

Further thought - it is common to see pipework painted to match the wall in kitchens or bathrooms, so where the bonding is verified to the clamp, does all accessible pipework have to be further verified? What readings should be expected if testing to pipework some distance from the bonding clamp?

 

[Vortigern]

I can not tell you how much it means to read these words

I was a bit careful about whether I should include that. But still, do try (to tell)
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I think that work that is not near water pipes would not necessarily mean anything. Bonding is in place to ensure ADS. So it would depend on what you are fitting exactly as to whether it in any way affected that aspect. But in any event I take that reg to mean that I must ensure that BS7671 is met re bonding before undertaking any work. As that would mean I am installing onto a safe(st) system in respect of an earth fault. So I see it as a fundamental pre-requisite. So I installed a shower in a domestic and of course checked the bonding not just look but measured the ohms. I got >1999 ohms on pipe 150mm away from the bonding clamp. Lucky I checked, visually the bonding was in place. In fact the connection could be pulled out of the screw clamp of the bonding cable. Also the cable was completely verdigris covered. So a new clamp/lug clean up of pipe, got .03 ohms. Can't be too careful it seems. Today, another job physically checked clamps on gas and water, loose water clamp. So it seems like a good idea to do more than just a visual.