bonding of main water plastic incoming

[kevyn]

I have recently heard of a local company not running a bond to the water main as he thought it was plastic incoming and plastic through the house. Turns out that it was plastic covered copper incoming. This happened on a big estate of new builds. Nic were involved with this major faux pa.

 

[Knobhead]

Ooopps

 

[ackbarthestar]

I started reading the first three pages then went off to find this article.....

 

[jibjob]

Yes there are. You are likely to get parallel paths from other extraneous services such as gas/oil which are mechanically connected to the same system as the water via boilers etc and not practical to remove.Disconnecting main earths and bonds still does not eliminate misleading readings.

Sorry to drag this up 2 months on but this is the first time I've seen someone mention parallel paths in respect of properties that have both water & gas/oil etc, one fed by copper and the other (usually the water) in plastic up to the stop tap then off round the property in copper. This issue arose for me the other day re mechanical connections at boiler etc thus meaning there would be continuity through the pipe work from the gas meter to the water intake. With the gas bond connected i'm getting 0.02/0.03 at the water intake (MET to pipework), this reading would rise to approx 0.2 with gas bond disconnected. Clearly the entire copper pipework system is extraneous but was unsure whether to bond incoming water. ELECSA told me that so long as I was getting a reading below 0.05 at the water intake with gas bond connected that the water needn't be bonded, hmmm.
This situation must be present in millions of properties where the water comes in in plastic & the gas in copper but only the gas is bonded. I've attended a few & have always gone for bonding the water (as a result of carrying out EICRs or small works) but am now in two minds.
I guess if you did an IR from MET to stop tap & you got above 22k then that would indicate that parts of the pipework were in plastic & that at least some of it would not be extraneous, effectively isolating the gas service from the water service.
Sorry to bang on :6:

 

[Deleted member 9648]

Sorry to drag this up 2 months on but this is the first time I've seen someone mention parallel paths in respect of properties that have both water & gas/oil etc, one fed by copper and the other (usually the water) in plastic up to the stop tap then off round the property in copper. This issue arose for me the other day re mechanical connections at boiler etc thus meaning there would be continuity through the pipe work from the gas meter to the water intake. With the gas bond connected i'm getting 0.02/0.03 at the water intake (MET to pipework), this reading would rise to approx 0.2 with gas bond disconnected. Clearly the entire copper pipework system is extraneous but was unsure whether to bond incoming water. ELECSA told me that so long as I was getting a reading below 0.05 at the water intake with gas bond connected that the water needn't be bonded, hmmm.
This situation must be present in millions of properties where the water comes in in plastic & the gas in copper but only the gas is bonded. I've attended a few & have always gone for bonding the water (as a result of carrying out EICRs or small works) but am now in two minds.
I guess if you did an IR from MET to stop tap & you got above 22k then that would indicate that parts of the pipework were in plastic & that at least some of it would not be extraneous, effectively isolating the gas service from the water service.
Sorry to bang on :6:

Remember though that the 'extraneous potential'- if I can refer to it as that -comes from outside of the property....generally from being in electrical contact with the general mass of earth. If there is mechanical continuity between a gas pipe and water system within the property that does not make the water system extraneous,it just means there is continuity between the services.You need to establish which of the services,water or gas,is in electrical contact with the general mass of earth outside of the property,and introducing it into the property.And thats where the 22k IR test is misleading IMO.

 

[oldtimer]

Yep I see where you are coming from I served my time as a 14th edition spark ie all connections should be Electrically and Mechanically sound so cables run in conduit / trunking with no earth wire as the containment was the earth. And on the water side because everything was run in copper with metal sinks so everything was earthed through the continuity great then came plastic pipes and the 15th edition that said earth everything that moves so Kitchen , Bathroom and Central heating pipework had to be supplimentry earth bonded. Giving spark the biggest Gad damn headache ie you earth both the gas and water then a year later the DNO changes it to plastic or 3 months later a plumber comes in to fit an outside tap doing it all in plastic and breaking the good mechanical connection to the rest of the prop.erty

I seen this in a property where the 6mm earth was bonding a 300mm piece of pipe at the stop tap where the incomer was plastic and somebody broke into the consumer side with plastic

 

[jibjob]

Remember though that the 'extraneous potential'- if I can refer to it as that -comes from outside of the property....generally from being in electrical contact with the general mass of earth. If there is mechanical continuity between a gas pipe and water system within the property that does not make the water system extraneous,it just means there is continuity between the services.You need to establish which of the services,water or gas,is in electrical contact with the general mass of earth outside of the property,and introducing it into the property.And thats where the 22k IR test is misleading IMO.

So where you have water coming in on plastic and copper throughout and with the gas intake as copper the 22k IR test is going to be meaningless unless you can isolate one from the other. In your opinon what's the best way to proceed where this scenario exists, bond both services regardless or just the gas assuming you're getting under 0.05 at the stop tap?

 

[D Skelton]

Quite simple really, you bond what is extraneous, you leave what isn't.

It is worth bearing in mind that just because a service enters the building in plastic it doesn't neccessarily mean to say that it is not extraneous.

 

[jibjob]

Quite simple really, you bond what is extraneous, you leave what isn't.

It is worth bearing in mind that just because a service enters the building in plastic it doesn't neccessarily mean to say that it is not extraneous.

The point I'm trying to make is how do you prove it's not extraneous without breaking the mechanical continuity of the copper pipe work which goes back to the metallic gas intake. As Wirepuller (rightly IMO) points out and I quote.....
"If there is mechanical continuity between a gas pipe and water system within the property that does not make the water system extraneous,it just means there is continuity between the services.You need to establish which of the services,water or gas,is in electrical contact with the general mass of earth outside of the property,and introducing it into the property"
It's less likely that a plastic pipe will be extraneous but while the two services are mechanically connected you can't be 100% sure. It's obviously not practical (and probably a waste of time anyway) to dismantle the central heating in order to carry out the IR test successfully so how would you proceed? Bond or not bond the water? This is the question.

 

[D Skelton]

I'd find which service was extraeous by breaking the bond between them and bond that. If both were extraneous then I'd bond both. If there was no way to break the link (internal parts of boiler for example) and categorically determine which of the two services was extraneous then I'd bond both.

 

[44ALLAN]

I luv this subject lol

 

[D Skelton]

I don't, its boring! Its all there in the regs and yet so many people still struggle to grasp the concept of it.

 

[jibjob]

I don't, its boring! Its all there in the regs and yet so many people still struggle to grasp the concept of it.

I don't struggle with the concept of bonding at all. I am interested in peoples thoughts on how they might broach this particular scenario, that's what's this forum is for innit, sharing ideas, knowledge etc with other electricians so that we can go about our business in a confident & safe manner.

 

[D Skelton]

I never said you did, I am just genuinely sick of talking about bonding!

 

[jibjob]

Fair enough :smiley2: