Domestic Earth Bonding Concerns and Advice Needed Please.

[makken]

I am currently renovating the missus house and have noticed a couple of things i need advice about, i am a qualified builder and plumber and have quite a bit of knowledge of domestic property electrics but i do 'NOT' carry out any electrical work myself as i do like to adhere to regulations :yesnod:. Anyway i believe we have a TN−C−S (P.M.E) System and the main earth conducter goes in to the little black box 'Main Earth Terminal' as shown in pic but my 'concern' is i have noticed that the main earth bonding to services goes from main earth terminal outside to the main earth terminal in the consumer unit, then from the consumer unit earth terminal the earth wire goes to the gas meter but this is my concern, from the same earth clamp at the gas meter the earth wire goes to the water pipe and is clamped under the sink. I thought the main bonding to services should be separate, so two separate earth wires from the consumer unit earth terminal to water and gas and correct me if i'm wrong but it is ok for the main earth bonding to services to come from the consumer units earth terminal.
Here are pics of the current way its wired 'diagram' and my outside meter box showing the P.M.E earthing terminal with earth wire going to consumer unit, and picture of inside wall where the earth from consumer unit goes through the wall to outside gas meter clamp and the the earth comes back through the wall from gas meter clamp to the water pipe under the sink.




One other thing, i have put in a new tap from the water main and one of those automatic water cut off switches, the water main pipe is plastic then as you can see i have the stoptap/drain valve then the pipe is broken again with the plastic auto shut off valve, so i'm assuming the new bonding clamp would be ok in the region i have circled green.

 

[telectrix]

using a common bonding conductor for gas and water is OK. the problem that could arise is that if 1 bond is dissed during alterations to plumbing or gas, then, if this was not reinstated, both bonds could be lost. the bond to the water should be close to the stop tap rather than under the sink.

 

[makken]

So is this earthing configuration acceptable under the current regulations or would it be best to have it changed so a separate earth from the consumer is going to the water pipe.

 

[telectrix]

all depends on the routing of cable. is it viable to run a separate 10mm to water? either way is acceptable. it's preferable to make a single bonding cable continuous. i.e. with any joints crimped so that removal of a connection from, say, a gas pipe, leaves the bond to the water intact.

 

[makken]

So if this is all ok then maybe just moving the earth clamp to above the auto shut off valve would be better, i don't know why it was clamped under the kitchen sink, this is how I found it.

 

[Spoon]

This is a question for anyone who knows, as I have not see these before.

What is the purpose of the automatic water cut off switch? Yes I know its to cut off the water, but why have one?

 

[makken]

This is a question for anyone who knows, as I have not see these before.

What is the purpose of the automatic water cut off switch? Yes I know its to cut off the water, but why have one?

Because if you don't have suitable access to the main valve for instance cupboards blocking it and you don't want to hack big holes in the cupboards, then you just mount the auto shut off switch in a cupboard and in an emergency you just flip the switch to shut the water off, as a plumber i'm a bit weary of them in case they ever fail and in the event of a major water leak you're kinda screwed if you can't get to the main stop tap but I know where my outside main valve is in the street and can get to it pretty quick so i'm not that bothered really.

 

[snowhead]

This is a question for anyone who knows, as I have not see these before.

What is the purpose of the automatic water cut off switch? Yes I know its to cut off the water, but why have one?

It's quicker than emptying the sink cupboard out to turn off a stiff stop tap.
It's easier for a person with no strength in thier hands, disabled, elderley etc.
It's easier than trying to find it when you don't know where it is.

 

[robsparky1975]

Is the incoming water service in PVC by any chance,the picture looks that way?

 

[telectrix]

if it's plastic incoming water, it should be blue.

 

[makken]

if it's plastic incoming water, it should be blue.

Its Black Plastic (Poly something), the houses on our estate are about 35 yrs old and this black poly plastic pipe was used on most if not all the houses on the estate, I know blue is currently used.

As I said earlier would the earth clamp under the sink on the cold water pipe be better moved to the area i have circled in green on the rising main picture, the incoming pipe is plastic then i have the stoptap then the copper pipe is broken again with the plastic auto shut of valve so you would have to clamp above that 'right'.

 

[robsparky1975]

Its plastic incoming so needs an electrician to do a simple test to check whether it is an extraneous conductor,a certain reading will confirm if any main earth bonding to the water service is even neccessary.