CU Change - No main earthing on water main. Polypipe incomer

[AMC]

Hi, Have completed consumer unit change. However there is no main bonding on incoming water and doesnt look like there ever has been. Have managed to locate incoming water supply and it is 20mm polypipe, the rest of the house is mainly run in copper. Im assuming it is my responsibility to get an earth sorted out, or am I able to list it as a deviation? (im using the job for my part p inspection on Tuesday!!!!)

 

[djb_1983]

Na you will have to make sure the earthing is in place yourself, otherwise the trade body your using will prob fail you for energising the supply without the adequate earthing in place.

 

[AMC]

I thought that may be the case! what a ****!!!

 

[johnboy6083]

if it is polypipe, then why bond it? its plastic. You are not bringing another potential into the installation, so imo no need for bond. Just note it on the Cert.

 

[AMC]

My main concern was really that pretty much the entire installation other than the incomer is in copper,including immersion heater etc, apart from the pipework under the bath which is Hep20 plastic. So do you think my inspector will accept this?

 

[johnboy6083]

if the installation is protected by 30ma RCD, then you dont need to bond the pipes, ie the old way of doing it under the boiler and sink. bu if its not too much hassle, then bond it anyway.

 

[AMC]

The new board is a Wylex dual rcd 30mA board. I understand having the 30mA RCD's pretty much covers me on supplementary bonding, is it ok for main bonding though?

 

[johnboy6083]

if the incoming is plastic then IMO, no need for a main bond. fresh water does not conduct electricity.

 

[Sintra]

Agree with above no need for main bond to a plastic service pipe.

 

[ringer]

Try phoning whichever scheme you are joining and ask their opinion. That way if your assessor says you done it wrong, you can say you took advice (from his employers). You've already paid your money - and advice is part of what you have paid for, so use it. Better than arguing "well guv, the lads on the forum said...."

 

[johnboy6083]

Try phoning whichever scheme you are joining and ask their opinion. That way if your assessor says you done it wrong, you can say you took advice (from his employers). You've already paid your money - and advice is part of what you have paid for, so use it. Better than arguing "well guv, the lads on the forum said...."

have to agree! its not our opinion that counts, its your assessors, and his heirarchy.

 

[ezzzekiel]

run a bond to where the copper starts and note it down

 

[telectrix]

if fresh wter does not conduct, then it's s waste of effort chucking an electric fire in the wife's bath

 

[johnboy6083]

The conductivity of a solution of water is highly dependent on its concentration of dissolved salts, and other chemical species that ionize in the solution. Electrical conductivity of water samples is used as an indicator of how salt-free, ion-free, or impurity-free the sample is; the purer the water, the lower the conductivity (the higher the resistivity). Conductivity measurements in water are often reported as specific conductance, the conductivity of the water at 25 °C

from wikipedia.

I used to install control equipment for water features. the method of telling th pumps when to empty a tank of water, was to use liquid level relays. these will tell you when the water is at a preset point by measuring its resistance. on these relays, there is a dial to set at which resistance the relay will activate. On tanks fed from mains, the relay would not work unless we set this dial at over 150,000 ohms. however i would not try to test this with your wife

 

[johnboy6083]

i would like to add to above, that i have been in a situation where i have meggared a cable where the ends were in dirty water, and it gave me a dead short. the dirtier water is, the better its conductivity.

 

[telectrix]

also depends on how fast you crank the handle on the megger

 

[Hawk81]

Well in my humble opinion to bring it back to the main question there is no need to bond the water pipe. as it is plastic then it is not needed. we bond as to stop a potential earth difference not to make sure that the rest of the copper pipes is earthed. surely any assesor will understand this or he should not be in his job.

 

[pushrod]

Not sure at all about this but isn't there a resistance value between the pipework and earth which shows whether or not something is an extraneous conductor or not and so if it will need bonding -> 20 KΩ and you don't need to bond??? or am i thinking of something completely different

 

[antimatter]

Section 4.4 OSG

The is no requirement to main bond an incoming service where the incoming service pipe and the pipework within the installation are both of plastic. Where there is a plastic incoming service and a metal installation within the premises, main bonding is recommended unless it has been conformed that any metal pipework within the building is not introducing earth potential. All bonding connections are to the consumers side of any meter, main stopcock or insulatinf insert.

 

[pushrod]

Section 4.4 OSG

unless it has been conformed that any metal pipework within the building is not introducing earth potential.

so how do you confirm that - is it what i said above? (on reflection is the figure 22 kΩ?)

 

[antimatter]

Simple answer - f$%k knows, anyone care to interpret for us?

 

[robsparky1975]

According to the on site guide,when polypipe incomer no main earth bond required as already pointed out,one of the first things i do when looking to upgrade to a new consumer unit is to check the sizing and connection of all earthing conductors,saves any problems later,anyway,one way of introducing earth potential might be an outside water supply in copper etc.mind you they say u dont need it on polypipe but on new builds i put it in just incase they change the regs in years to come and say its needed.

 

[Johno]

As already said, if it is a plastic pipe then no need to main earth bond, but you still need to make sure that the resistance is low between pipes and class II equipment in the bathroom (sorry I have forgot the formula) to rule out supplementary bonding.

 

[Johno]

If it were me having my assessment I would bond it.

 

[telectrix]

Bond it. they can't fail you for overdoing it, but they can if the assessor thinks it should be done and it ain't

 

[pushrod]

As already said, if it is a plastic pipe then no need to main earth bond, but you still need to make sure that the resistance is low between pipes and class II equipment in the bathroom (sorry I have forgot the formula) to rule out supplementary bonding.

touch voltage of 50V and current thru rcd of 30mA (0.03A) so R = V/I = 230/0.03 =1667ohms
if R is < 1667 Ω no supp bonding needed

 

[Des 56]

Aside from the main topic of whether main bonding is needed or not

If you decide that it is not going to be installed
You must carry out supplementary bonding in the bathroom because you can not meet the conditions for ommision
It has to be a building with protective equipotential bonding to do so

There seems to be a lot of opinion saying not required,my own understanding is that a full cooper system would require the main bond ,whereas if the supply and major parts of the plumbing are plastic then omit

 

[Spudnik]

Again, i agree with Des.

However, if im doing a rewire, then ill always throw in a bond, even if not needed due to poly incommer.

Wasteful? ... Maybe.

 

[nickblake]

Had a house that had no bond to water and a radial circuit with 4 sockets on it a cold water feed to a pump due to low pressure on the icoming main plugged into a socket on a radial plug a socket tester in all ok Zs the socket high readings , socket tester in reading unplug the pump earth fault the house was all plumbed in plastic but was finding a small earth through the water so there is still the potential from the water service be it only small its possible if its copper , but asringer has been said contact your trade body for advise,personally i would install the bond, always do

 

[Deleted member 9648]

IMO a main bond should be provided on the first available section of copper...even if the service is not introducing an earth potential at the time of the install conditions may change......CYA.

 

[antimatter]

As already said, if it is a plastic pipe then no need to main earth bond, but you still need to make sure that the resistance is low between pipes and class II equipment in the bathroom (sorry I have forgot the formula) to rule out supplementary bonding.

Sorry , but do you mean Class I?

 

[Johno]

Yes, well done for spotting my deliberate mistake.

 

[oldtimer]

4.4 OSG is saying you do not have to bond if both supply and house pipework is plastic but if supply is plastic and house is copper then recommend you earth it in other words earth the bl+%6 pipework if metal because if you dont then Jobs Worth inspector who is probably reading forums like this will pull you up for not doing so and why would he do this ? because he can and he has the power to say sorry you fail and I am just doing my job and this is how I show my manager nothing gets past me.
What I would say is this environment suffers from the lack of definition and open season on interpitation but what I have learned is if you go up against the people who police our trade then human nature dictates that they dig in because they can.