Earthing of Copper Water Pipees

[snowflake]

Hi
I have a modern bungalow (10 Years Old) which has one earth lead connected from mains in to rising water mains in and all pipework is brass/copper.
My son has purchased a 1890's house in which all pipe work in the kitchen/bathroom is bonded.
We are fitting a new kitchen & bathroom suite.
Whilst I can see the need for bonding the rising main in the kitchen and all the pipe work due to appliances that might be used in close proximity to the Taps/Sink unit, is this level of bonding also necessary in a bathroom (bearing in mind all the plastic plumbing fittings that can be used) when the light/fan switch is external to the bathroom and no other source of power available.
Many Thanks (In Anticipation)
Great Website)

 

[securespark]

There are several trains of thought on this one:

According to popular opinion at the IEE, the reverse of your logic is true.

The IEE say that bonding copper pipework and metal sinks in the kitchen is no longer deemed necessary, but that bonding to extraneous metalwork in the bathroom is imperative, and not just to pipework, and radiators etcetera, but to the cpc (earth) of any appliances in the bathroom, too. Like for example, shower, immersion heater, wall heater, fan, light, shaver socket etcetera.....

There are limitations: plastic piping need not be bonded. The IEE say that radiators fed by plastic piping do not present a risk, and therefore do not require bonding but others think they are and do.

The NICEIC concur that bonding of (eg) an electric towel rail is unecessary, as long as you have bonded to the cpc of the supply cord.

The reason bonding in the bathroom is deemed so important is that there is reduced body resistance in there: ie you are naked, without footwear, and wet. This greatly increases your susceptibility to an electric shock.

Main bonding is also required to the gas main (consumer's side) if present and any other metallic services, like oil. Also to be bonded are ducts and exposed metalwork like RSJ's. Main bonding to the water should be effected on the consumer's side of the stopcock, as close as is practicable.

This is a widely discussed topic. Please search for earthing and bonding, supplementary bonding in the bathroom and other relevant terms and I'm sure you'll pull up a mine of information to mull over!

 

[ban-all-sheds]

There are several trains of thought on this one:

Several???

According to popular opinion at the IEE, the reverse of your logic is true.

And according to the wiring regulations - not just popular opinion. Unless you think the wiring regs are popular....

The IEE say that bonding copper pipework and metal sinks in the kitchen is no longer deemed necessary, but that bonding to extraneous metalwork in the bathroom is imperative, and not just to pipework, and radiators etcetera, but to the cpc (earth) of any appliances in the bathroom, too. Like for example, shower, immersion heater, wall heater, fan, light, shaver socket etcetera.....

I think this is where people start to go wrong. The requirement is not to bond "extraneous metalwork", is is to bond extraneous-conductive-parts, the definition of which is (with my emphasis):

A conductive part liable to introduce a potential, generally earth potential, and not forming part of the electrical installation.

There are limitations: plastic piping need not be bonded. The IEE say that radiators fed by plastic piping do not present a risk, and therefore do not require bonding but others think they are and do.

Then those others are WRONG - if a radiator is fed by a plastic pipe it cannot introduce a potential.

 

[securespark]

Ban I tend to agree with you, but I was putting both sides of the story so to speak. Anyway, the guy can look up stuff and make up his own mind.

Somehave said in the past that rads can still become live even if they are iso'd by their supply pipes, and that is their reasoning behind it.

Paul Cook did tell me once that to earth in some cases is more dangerous than not to earth. He would prefer an earth free environment in the bathroom.

 

[ollski]

Serviced a boiler the other day, ran the fluke pen around it first as you do .....it seemed ok, prelim elec checks seemed ok so I switched off at the spur, removed the fuse and stripped it down. I disconnected the gas valve and went to remove the burner by holding the gas pipe in one hand and valve in the other and watched the spark fly across my arms before I jumped backwards across the room. Turns out the whole pipework and boiler was live with 180V and also the rads. Fortunately all the taps had been connected with plastic fittings and not bonded across so the customers were unaware of a problem, so in this case not bonding was a godsend ( for them, not me!). Not sure why it didn't trip the rcd on the main board though, I ended up just isolating the ring main and getting them to call in the meb. I ordered a new fluke pen aswell!!

 

[ban-all-sheds]

The original wiring was probably done by a plumber....

 

[rockingrodders]

So what happens if you live in a fairly modern house (circa 1975) that was built before the regulations were changed and there is no earth bonding?

 

[plugwash]

truthfully there isn't much danger

any reputable sparky will check bonding first though

 

[kendor]

Then those others are WRONG - if a radiator is fed by a plastic pipe it cannot introduce a potential.

I think YOU are wrong on this you stated above the fact of introducing a hazard such as an earth potential so what is inside a radiator then? Water that could make the radiator a different potential!

 

[plugwash]

paul cook wrote a good peice on this one

long narrow runs of water very very quickly get up into the range of resistances that are considered to be insulators

 

[kendor]

paul cook wrote a good peice on this one

long narrow runs of water very very quickly get up into the range of resistances that are considered to be insulators

if the water was pure without minerals then it could be considered an effective non conductor but the water in radiators contain all manner of things including inhibitors etc and the relatively short runs in a domestic premises would make the thesis above probably(having not seen it) redundant the fact is,even a small amount of conductivity may be enough to cause harm to human life and therefore is not acceptable.

 

[dingbat]

Actually, kendor, you should read the article because all that you mention is covered and the conclusion is that the water in any kind of domestic pipe system, along with any chemical additives can be considered to have negligible conductive properties.

Maybe somebody here can post up a link to that article?

 

[kendor]

yes, i would be interested to read it if you can find the link, i tried to do a search with his name but was unsuccessful

 

[plugwash]

i think heating system pipe was quoted as 20K/meter (no i can't find the peice right now)

and to make even 10ma flow at mains voltage you need a resistance of 24K

also it must be remembered that earthing itself (earth free equipotential bonding is unheared of in domestic setups because of the precautions needed at the border of the earth free environment) whilst protecting against indirect contact *INCREASES* the danger in the event of direct contact

 

[murraysnudge]

Is this it?