Max water bond resistance

[Ampo]

Hi all so I have a situation where a client is moving and they want the db changed for selling. Db change is easy enough as is running a bond to gas which is currently missing. The only issue is that the last eicr said that the water wasn't bonded. It would involve major works (tiled floors and newly decorated walls, coving and so on) and the mains water is opposite side of the house. Although the strap isn't visible I have run a wander lead and got 0.29 on a 6mm at the dB to the stop cock so it is bonded. I know its not a good reading but wonder what peoples opinions are in changing the board? There is no way they want the work done if it involves ripping the house apart for the water bond but they are more than happy to do the board and gas.

 

[Pretty Mouth]

Hi all so I have a situation where a client is moving and they want the db changed for selling. Db change is easy enough as is running a bond to gas which is currently missing. The only issue is that the last eicr said that the water wasn't bonded. It would involve major works (tiled floors and newly decorated walls, coving and so on) and the mains water is opposite side of the house. Although the strap isn't visible I have run a wander lead and got 0.29 on a 6mm at the dB to the stop cock so it is bonded. I know its not a good reading but wonder what peoples opinions are in changing the board? There is no way they want the work done if it involves ripping the house apart for the water bond but they are more than happy to do the board and gas.

.29 ohms = 94m of 6mm cable, or more likely a loose connection. Could you not run the bond around the exterior of the building?

 

[suffolkspark]

You sure it needs doing at all?

 

[davesparks]

could you elaborate on how you tested this please? was this tested with the 6mm disconnected from the MET?

 

[telectrix]

is there a gas pipe anywhere near the water stop cock, or could the water bond be connected elsewhere ( as in as close as practicable to the incomer without demolition)?

another solution would be to get a wet-pants to fit a plastic section close to the stop cock

 

[Ampo]

.29 ohms = 94m of 6mm cable, or more likely a loose connection. Could you not run the bond around the exterior of the building?

I know its really high and realistically only a 20m run, its a terrace with board at the front and stop cock at the back, gas meter i van do externally but no chance on water
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could you elaborate on how you tested this please? was this tested with the 6mm disconnected from the MET?

Yes so I did a lknd lead test with some 1mm singles from the db position with the 6mm disconnected to the stop cock. Singles were nulled out

 

[Baddegg]

I know its really high and realistically only a 20m run, its a terrace with board at the front and stop cock at the back, gas meter i van do externally but no chance on water
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Yes so I did a lknd lead test with some 1mm singles from the db position with the 6mm disconnected to the stop cock. Singles were nulled out

As tel said get a plumber to put a section of plastic in at the point of entry of the pipe

 

[Ampo]

is there a gas pipe anywhere near the water stop cock, or could the water bond be connected elsewhere ( as in as close as practicable to the incomer without demolition)?

another solution would be to get a wet-pants to fit a plastic section close to the stop cock

Unfortunately nothing anywhere near where I could get to. The board is at the front door

 

[pc1966]

If bonding is utterly impractical, then what about fitting a 100mA delay RCD incomer instead of the main switch and converting it to a TT system? You would need an earth rod, but that might be more practical then ripping up expensive floors.

Just another idea to be discussed!

 

[suffolkspark]

I find it odd that the incoming water supply isnt plastic..... only come accross half dozen lead ones in 17 years

 

[Pretty Mouth]

I know its really high and realistically only a 20m run, its a terrace with board at the front and stop cock at the back, gas meter i van do externally but no chance on water

Out and up the front wall to the eaves, in through the loft, then back out and down the back wall? Assuming loft hasn't been converted.

I like telectrix and Baddegg's idea best

 

[Ampo]

I find it odd that the incoming water supply isnt plastic..... only come accross half dozen lead ones in 17 years

Loads here in South Wales, Its a mix but seems lots havent been replaced
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I understand why these regs are in place but it does seem stupid when the likely outcome will be the client leaving a wylex wooden backed board in place and no gas bond

 

[pc1966]

Does it have supplementary bonding of hot-cold pipes, and water-gas at the boiler?

If so, and you bonded to the gas supply, would you then see a very low resistance (of the order of the magic 0.05 ohms) from gas bond to water stopcock?
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The 0.29 ohms you are seeing might be from the boiler's CPC, or gas hob ignition CPC, etc.

 

[HappyHippyDad]

Does it have supplementary bonding of hot-cold pipes, and water-gas at the boiler?

If so, and you bonded to the gas supply, would you then see a very low resistance (of the order of the magic 0.05 ohms) from gas bond to water stopcock?
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The 0.29 ohms you are seeing might be from the boiler's CPC, or gas hob ignition CPC, etc.

Clever thinking, but are you saying this would then be OK?

 

[David Prosser]

I find it odd that the incoming water supply isn't plastic..... only come across half dozen lead ones in 17 years

Lots of 22mm, 3/4" and 1" copper or galv' supplies. Lead supply pipes were stopped in 1970 and copper or galvanised steel ones used. Early 70's meant mixed imperial and metric. These were superseded by the black plastic ones mid 70's early 80's (often still found used for "ducting" to outbuildings).The MDPE pipe was available form the late 50's but never took off then. The newer blue one should have either a tracing strip built in or wire inserted so they are easier to find with a CAT and genny. Unforunatly the majority of the ones installed before 2000 don't have this!

 

[pc1966]

Clever thinking, but are you saying this would then be OK?

Is it done the way the regs say? No
Is it achieving the goals of the regs? Yes
When comparing the do-nothing option of leaving the old Wylex rewirable CU in place with no bonding, with a replacement RCD/RCBO-based CU and a bonding-by-pipework option, I would have say it is a massive improvement in safety.

 

[davesparks]

I find it odd that the incoming water supply isnt plastic..... only come accross half dozen lead ones in 17 years

Likewise I have only come across a handful of lead water mains still in service. But I have come across plenty of iron/steel ones.
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I may have missed it, but I don't see anywhere where the OP has told us what the earthing system is yet, and nobody appears to have asked.

If it is TT or TNCS then it likely is OK with a 6mm main bond.

 

[David Prosser]

If it is a lead supply pipe then report it to Welsh Water (if that's the supplier) they should replace it FOC.

 

[Ampo]

System is tncs and it is copper coming out of a floor board at the rear of the house. I could go ripping these up but wasn't going that far on a quote for obvious reasons. Could be anything coming in, I can't see, jouse is victorian
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Is it done the way the regs say? No
Is it achieving the goals of the regs? Yes
When comparing the do-nothing option of leaving the old Wylex rewirable CU in place with no bonding, with a replacement RCD/RCBO-based CU and a bonding-by-pipework option, I would have say it is a massive improvement in safety.

This is my thinking, its one of those situations where it'll probably all get left an old mess

 

[pc1966]

This is my thinking, its one of those situations where it'll probably all get left an old mess

That is why I would probably see if good gas supply bond & supplementary bonding of hot/cold/gas pipes where accessible is enough to measure the water pipe as well-bonded. It might not follow the specific guidance to the letter, but it does the necessary job.

After all, if you did an inspection and found no sign of water bonding but it measured 0.05 ohms to the MET, how would it be coded? C3 at most. From the best practice guide:

C2 for: Absence of effective main protective bonding of extraneous-conductive-parts entering the premises

C3 for: Main protective bonding to gas, water or other installation pipe is inaccessible for inspection, testing and maintenance, or connection not made before any branch pipework.

My emphasis on the "effective" aspect. Not doing the upgrade to an RCD/RCBO board in my mind is far more dangerous than leaving as-is, so insisting on by-the-regs water bonding that the customer will reject would be a case of perfection as the enemy of good.