Supplementary bonding across plastic section of pipe

[kingeri]

8.5kw shower supplied by copper pipe......with plastic T where water supply branches to serve it, then back to copper. Any need to bond across the plastic T? Similar story with water supply to bath on hot and cold. All circuits RCD protected, shower itself earthed no problem.

 

[kingeri]

Incidentally, this is a debate between myself and the homeowner.

 

[malcolmsanford]

Does the installation comply with regulation 701.415.2 with regard to supplementary equipotential bonding ?

If not then is that piece of copper pipe an extraneous conductive part.

If yes for 1 and if no for 2 then ........ then no you do not need to bond across the plastic.

 

[telectrix]

the way to establish whether of not the copper after the plastic is extraneous is: IR test from the MET to the suspect pipework. if the reading is < 23Kohms, bond it. if it's> 23Kohms, don't. simplesss

 

[kingeri]

Thanks guys. I already did the IR test this morning. I established in my own mind that it doesn't need bonding. The homeowner showed me under the floorboards on the landing and there are about 12 plastic Ts and elbows coming off copper. The plumber has bonded across them all....the homeowner said the plumber told her to make sure I do the same when I'm putting the shower in. I argued that it would probably not be necessary, but she gave me 'the look' (I don't trust you / you don't know what you're doing). The plumber has also used bits of 2.5mm T&E earth sleeved to do the 'bonding'. I have told her that even if it is established that bonding is necessary in a location, the stuff the plumber has used is totally wrong........ I'm going back after 5 o'clock. Can't wait.

 

[sedgy34]

nah you need to cross bond all plastic too as it states in the stupidity regulations book latest edition!! lol

 

[malcolmsanford]

Then start quoting her the regs, and what Tel said that you did a test and this and that, and basically tell her he is plumber, and you are the electrician, and you will even put on your certificate that you have IR tested the pipe it was ............ Kohms and therefore 230/ by your result gives you 0.0............. whatever milliamps and that will give you a touch voltage of ................ blah blah blah .......................let the plumber argue with that one

 

[telectrix]

better still. get her to ask the plumber what test equipment he used to determine that it needed bonding.

 

[drew35]

On a similar thread, I went to a job today where a customer had received an electric shock whilst in the shower. Its purely gravity fed, no electricity involved, but the mixer is metal and its fed by surface mount copper pipes that run up into the loft where they join plastic. As the water main is plastic there is no bonding. When he turned off the shower he received a shock and the rcd tripped. So my theory is some appliance in the house is introducing the current into the water, and because there is no bonding the rcd didn't trip until a naked man standing in water earthed it out. The fault wasn't present on arrival so I've temporarily bonded the pipes to the nearest socket, going back tomorrow to get involved. . . What I think I'm saying is, if in doubt bond it, then charge for the pleasure, everybody's happy!

 

[telectrix]

some appliance in the house is introducing the current into the water,

can't see that, myself. clean water doesn't conduct.more likely an earth fault on an appliance to pipework. i'd test to see if there is any voltage present on the shower taps/pipes relative to the MET. ( with appliances switched on and off in turn)

 

[kingeri]

Just got home from seeing the lady, I briefly explained the situation. She was happy with what I told her in the end. I did explain that there is a lot more to electrics than meets the eye....no disrespect to plumbers but you can usually see when a pipe is leaking.....it's not so obvious when you've got earth leakage etc. I suggested in future she let's a spark do her electrics.....including bonding! I did also make the point that I could have bonded at half a dozen points in her bathroom....and heck why not bond the kitchen sink too....and charged her for the pleasure.....but I didn't cos it was totally unnecessary!!!!

 

[kingeri]

On a similar thread, I went to a job today where a customer had received an electric shock whilst in the shower. Its purely gravity fed, no electricity involved, but the mixer is metal and its fed by surface mount copper pipes that run up into the loft where they join plastic. As the water main is plastic there is no bonding. When he turned off the shower he received a shock and the rcd tripped. So my theory is some appliance in the house is introducing the current into the water, and because there is no bonding the rcd didn't trip until a naked man standing in water earthed it out. The fault wasn't present on arrival so I've temporarily bonded the pipes to the nearest socket, going back tomorrow to get involved. . . What I think I'm saying is, if in doubt bond it, then charge for the pleasure, everybody's happy!

Hasn't there been experiments done fairly recently that prove that clean (ie tap) water is an extremely poor conductor of electricity....especially over a distance.

 

[telectrix]

yep. pure water ( can't say tap water is pure. more chemicals than ICI ) is not a conductor.

 

[Engineer54]

Dissolved conductive parts in water will be different from area to area in the UK, and that content can change almost on a daily basis. This is an old chestnut, but generally the harder the water the more conductive it will be.... I wouldn't trust any of the modern day water boards reports on there water supplies, most are just complete fabrications to cover there arse!! lol!!!

 

[telectrix]

agree. our tap water smells like a council run swimming pool. more chlorine than domestos.