Discuss Bad reading on bonding, plastic fittings? in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net



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Hello all I'm looking for some advice please.

I been out today to change a CU and when testing the 10mm water bonding I am getting a reading of 0.25. The stop tap is in the bathroom with all tiles around it, I can't see the bonding clamp so I tested to the nearest pipe.

I noticed that the pipe fittings near the stop tap are the push fit compression ones so I am guessing this is why I'm getting a bad reading.

My question is what should I do, I've looking under the sink in the kitchen and the pipe work seems to be all copper including the joints. Should I bond to here?

I plan to use this for my NIC assessment so need to get it spot on.

Scolmore Electrical Products
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does the water supply pipe or the customers supply pipework meet the definitions of an exterraneous conductive part? You need to check this by :

Turn off main supply.
Disconnected supply earth from MET.
Test with wandering lead to all pipework that you can see. (obviously with one end connected to the incoming earth)
If any of the readings are below 22.5 kOhms you should bond the pipework.

Bear in mind if the supply was plastic, but there was a length of copper/ steel running under the concrete floor to another area, this may well be an ECP although the main supply end may not be, therefore I would bond to the part(s) which are exterraneous conductive parts


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  • #3
Rember that bathrooms are not always fed off the mains water. check your reading at the kitchen cold water tap that will be off the mains. then check as above.

SirKit Breaker

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  • #4
Is it possible to fit a new clamp and bonding cable? I know it is supposed to be within 600mm of this that and whatever, but this is the real world, and the regs are guidance. If possible i would bond it where you can, it doesn't take fault current much longer to travel a few more metres down a bonding cable if it is not within 600mm, just bear in mind that you still need a maxmum value of 0.05ohm, so you may need a 16 instead of a 10mm for example if you need to fit a long one.

Just a thought, but if you are using a long lead to check between the MET and pipework, have you nulled the leads?


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  • #6
Hi thanks for all the replies, it's not a long run from the MET so 10mm should be fine. I can't see the bonding clamp or the cable near the stop tap all I know is there is 2 10mm cables at the MET one is for the gas so the other one must be for the water, god knows where they clamped it to though.

Im going back next Friday and I'll test the resistance at the pipe work under the kitchen sink and see what I've got there.

Failing that should I run a new 10mm cable to the cold water pipe under the kitchen sink where the pipes seem to be soldered together?

Or I could try and put a new clamp near the stop tap and run a new 10mm to there and disconnect the old one? But this might be a pointless exercise as it looks like the copper pipe work coming off the stop tap to the bathroom sink has plastic joints.


Amp David

Testing between all the pipework you can see, are we on about supp bonding in this case?

New CU so why go round testing between all visible pipework?
SS can I ask why your disconnecting the earth for an IR test mate ...............................
When I test domestics I quite often come accross lack of bonding etc, and like to test the services to see if they are ECP's. On an existing install I just find it easiest as there are often paralell paths to earth throughout the install (i.e. boilers/ water htrs./supplementary bonding). I don't do it on the IR scale though just on the kOhms.


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  • #10
Just a thought, you say you can't see the earth clamp on the water pipe work. I havent checked in the book but I thought that all bonding clamps have to be accessable?
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