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Topic Title: A bit of advice re main bond to water and a CU change
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Created On: 18 April 2014 02:43 PM
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 18 April 2014 02:43 PM
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aligarjon

Posts: 2916
Joined: 09 September 2005

Just after your thoughts over bonding to water whilst doing a CU change guys please.
I looked at a job this morning where i need to change the CU. i checked where the stoptap is, downstairs bathroom with the end of the tap stuck out of a nicely tiled soil stack boxing down the side of the W/C. tiled floor. (wooden so limited access generally underneath. although not under the bathroom as the solid walls go down below. i have worked in a few of these before so know the general layout and where i can get at.
There is no chance of getting anywhere near the tap with a main bond without smashing the tiling up. The incoming water pipe on all of the previous ones on this estate is pvc.

What are your thoughts on bonding onto pipework whereever i can get to it (reasonably practical) and a note on the certificate as to its location once i can find somewhere suitable. i would also recommend it be put in the correct position if the bathroom were refurbished at a later date.

I would be able to test continuity from the bond position to the tap obviously. There is a chance the bond position would be below floorboards but what can you do.


Gary

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Specialised Subject. The Bleedin Obvious. John Cleese
 18 April 2014 02:46 PM
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geoffsd

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'Where practicable'
 18 April 2014 02:48 PM
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JZN

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Is the CU near the boiler? I often go for that in awkward situations as you get the water and gas there and it's easily visible.

John
 18 April 2014 02:53 PM
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daveparry1

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Yes Gary, where practicable is the key! I've often put the bonding onto the water in the loft if the mains goes up there in copper, in fact I done one like that only this week. I have put both water and gas bonding in some very questionable places as far as the regs. go and even used such jobs on annual assessments and never been criticised for it as long as there is a good reason (and not just lazyness!)
 18 April 2014 05:54 PM
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aligarjon

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Cheers Guys. i have just been trying to locate a post re using the gas pipe as a bonding conductor i remember reading but can't find it. As a last resort would i be able to use the gas pipe and bond across at the boiler with apropriate labelling.
( so bond the gas at the meter then loop from the gas to the water at the boiler)

Gary

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Specialised Subject. The Bleedin Obvious. John Cleese
 18 April 2014 06:29 PM
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daveparry1

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I done one similar a few weeks ago Gary, c/unit and gas meter were very accessible but the incoming water was at the other end of the house, (tiles, laminate flooring of course!) so I did a continuity test between the rising main and the cold mains inlet to the combi boiler and got 0.0 something ohms so I bonded the water there. I'll probably be using this job for annual assessment in a couple of months time so we'll see if anything's said!
 18 April 2014 07:19 PM
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aligarjon

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Thanks Dave.


Gary

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Specialised Subject. The Bleedin Obvious. John Cleese
 18 April 2014 08:00 PM
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spinlondon

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If the water main is PVC, then why are you considering bonding?
 18 April 2014 09:21 PM
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napitprofessional

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Originally posted by: spinlondon

If the water main is PVC, then why are you considering bonding?


I was thinking the same thing myself ....

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B. Eng (Hons) MIET
 18 April 2014 09:40 PM
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daveparry1

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Both you and Spin are correct of course napit, regs -wise there is no need to bond water if it comes in in plastic but personally I always feel happier, if there's a fair amount of copper in the house if it is bonded.
I feel many people on here spend too much time trying to comply to the letter of the regulations, they are after all a guide!
Having said that, there are times, like the one we're just talking about when doing something which isn't absolutely necessary to comply with regs could be of benefit under certain fault conditions.
 19 April 2014 01:58 AM
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spinlondon

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So we have the choice of un-bonded metalwork which will not provide an earth fault path, or bonded which will?
I wonder under what fault conditions, bonding the metal work would be of benefit?
I also wonder what would happen to the metalwork, if that very event occurred, a supply neutral fault?
 19 April 2014 07:58 AM
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MrP

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Gary
Just as a matter of interest the reason for doing a consumer unit change?
MrP Day4
 19 April 2014 08:58 AM
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aligarjon

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The reason for the change was purely the customers rerquest, there are no other works planned at this stage other than the bonding. To be fair it could do with upgrading, theres a 4 way metalclad fusebox squashed in the meter box and a further ex storage heater fusebox in the hall via henley blocks.all from early 1970's.
I purposely mentioned the probable plastic incomer on the water pipe although i am not sure if i can definitely confirm it. I am going to need to try and find a way to test it, which may be problematic due to unknown and known parallel paths via a back boiler and tank etc.
I don't see as a seperate bond can possibly add a potential hazard as it will be connected through the other pipework anyway.

Gary

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Specialised Subject. The Bleedin Obvious. John Cleese
 19 April 2014 11:09 AM
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daveparry1

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Spin,
I always think of a fault which could result in the metal pipework becoming live, eg cable trapped under a hot pipe for instance or a faulty electric shower etc. causing the supply pipe (if metal) to become live. I know the earthing should take care of all of this and of course the rcd if there is one, which I doubt in this case, if there's no main bonding I doubt there's an rcd either!
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