5 ft of plastic

[panny300]

mains water pipe from stopcock in kitchen is copper for about 2ft then changes to plastic for about 15ft,then back to copper through rest of house, where should it be bonded ?

 

[Softus]

On the copper, within 300mm of where the copper enters the equipotential zone (subject to correction by someone who knows more than I do about this stuff).

 

[plugwash]

you definately need to bond the metal section that enters the ground.

whether you should also bond the other metal section is more open to debate. It can't introduce a potential into the equipotential zone from outside but it can carry potentials arround the building (pipes are usually routed near cables in my experiance).

imo the best thing to do would be to take a single unbroken run of earth cable first to the clamp on the metal section that enters the ground then clip it along the pipe and attatch it to the rest of the metal pipework.

 

[Softus]

Isn't the risk you mentioned mitigated by supplementary bonding of extraneous conductive parts?

 

[plugwash]

in practice the large network of pipework will probablly get earthed by supplementry bonding somewhere yes but that is done to far lower standards than main bonding.

 

[Softus]

far lower standards

 

[plugwash]

less than half the cable size, no requirement to keep unbroken runs for multi item bonds, connected to main earth only through piddly circuit CPCs.

i consider that far lower standards than those for main bonding.

 

[Softus]

OK I get you. But surely the potential (pun intended) hazard is much lower for differential ground voltages that arises within the home, compared to those coming from outside?

So although the protection is lower in supp. bonding, is the standard actually lower?

 

[Pensdown]

you definately need to bond the metal section that enters the ground.

whether you should also bond the other metal section is more open to debate. It can't introduce a potential into the equipotential zone from outside but it can carry potentials arround the building (pipes are usually routed near cables in my experiance).

imo the best thing to do would be to take a single unbroken run of earth cable first to the clamp on the metal section that enters the ground then clip it along the pipe and attatch it to the rest of the metal pipework.

Which regulation calls for that and what would it achieve?

 

[ban-all-sheds]

It can't introduce a potential into the equipotential zone from outside but it can carry potentials arround the building

15' of plastic pipe containing clean water sounds like a pretty good insulator to me...

 

[plugwash]

yes but after that plastic pipe its going to be running round the building potentially sharing notches with cables etc.

 

[ban-all-sheds]

Yes but that does not make it an e-c-p.

 

[ebee]

no it`s a potential ecp though .
I`d feel happeir earthing it.
Try passing 250V from an insulation tester thru 15 foot of clean water to your hand - it will bite you

 

[ban-all-sheds]

Have you tried it?

If it's 22mm pipe 250V will push 0.8mA through that much water, 15mm and it's 0.5mA.

 

[ebee]

Yes I have (on other people)