Water becoming "live"

[partplonker]

I recently did a load of work making good a poor installation for a friend who just bought a flat. I have some electrical qualifications and 30 years experience, but I'm not a member of a CPS because I don't do enough notifiable work for it to be worth paying the subs.

When it came to bonding, I only bothered bonding the gas and didn't bond the water pipes. I did this because the water incomer is plastic to 1 foot above the floor in the kitchen. There's literally 1 foot of 15mm copper pipe connected to the plastic incomer in a cupboard under the kitchen sink with a stop tap in it and after that, it's all plastic joints and more plastic again off to the boiler and shower.

Once I'd finished, I got a CPS registered electrician out to do a condition report on the place for me so that my work had been verified by someone else. I explained my reasoning for not bonding the water and asked if he was happy with that.

He told me that I had to bond the water, even if it's plastic because the "water can become live".

Is this a thing? I can't find anything about live water in my regs book on the subject of bonding water pipes. I thought the point of bonding metal pipes is that if they were stuck in the ground somewhere, they might introduce a dangerous earth potential into the installation? I don't really see how that can happen with plastic pipes.

I've added the bonding as he requested since I don't see it can do any harm. Was I missing something?

 

[telectrix]

the guy speaks through his arse. you were right in what you did. the acid test is to IR test from MET to pipe. if >22k Ohms then it's nort extraneous and doesnot require bonding.

 

[cliffed]

Recently had this issue with the Niceic man.
Being old school you would of bonded it,but these days if the entry into the premises is plastic then no need to bond .
Even when copper pipework comes away from the plastic pipework.

 

[OnlQQker]

Funny you posted this when I was just reading through an old thread about it. Earthing water. Part plastic, part copper | ElectriciansForums.net

I wondered the same thing after talking to a girl who said she uses curling tongs whilst laying in the bath!

 

[JBW175]

That’s two in two days we’ve had on this subject.

As above, no need to bond, it’s a waste of cable.

 

[loz2754]

411.3.1.2
Metallic pipes entering the building having an insulated section at their point of entry need not be connected to the protective equipotential bonding.

If in doubt, do the resistance test as @telectrix said.

 

[partplonker]

Thanks everyone. I did IR between the copper and MET and told the guy I had, I got > 500 megohms

 

[DefyG]

"water can become live".

Perhaps he thought it was April 1st.

 

[telectrix]

Perhaps he thought it was April 1st.

he probably believes in santa as well.

 

[Lucien Nunes]

Theoretically if the water is conductive enough, it could bridge the gap between the metal pipe in the ground and some other unbonded section of metal pipe accessible to the touch, with a low enough resistance to introduce the ground potential into the equipotential zone. However, in that case, the water is probably badly contaminated and a miniscule risk of electric shock is overshadowed by whatever poisoning you are likely to get from it.

In water-cooled high power electronics where the hot-side heat exchangers are at high potentials and isolated by plastic piping, it is necessary to de-ionise the water and monitor its purity to ensure it remains a good enough insulator not to cause earth leakage and electrolysis in the cooling system.

 

[FatAlan]

I believe the great JW did a video on the conductivity of water. As above, it will vary according to what solutes it contains.