main bond

[SimpleSimon]

Maybe I've missed the post, but when you went to the main stop cock to check for the bonding clamp, was it plastic or copper than on entry?

 

[NMc]

Let me recap

You are doing a PIR. all you can see if copper pipes and a tank and you can't find any plastic. You get a reading of 320K between MET and water pipe

Sound to me like you have extranuous metalwork which under the regs needs to be bonded. You have 320K reading which suggests to me there may be some kind of conection but not good enough

The property is 3 years old so likely to have a TN-C-S supply which under the ESQCR need the water pipes to be bonded yet you cant find it, so has the original been installed incorrectly?

The 320K between MET and water pipe would suggest no main bonding or a bad termination

You can prove the continuity of the pipework through tests at all the different water outlets with a long lead if you get low readings the pipework is continuious. This will let you know if one bond connection at point of enty will be sufficient. You may need to consider some supplementry bonding

The bottom line is you are carrying out the PIR as a competant person and you will sign the cert as so. Anything wrong could bite you

 

[pushrod]

If you have a resistance between a metal part and the MET of 320kΩ then the metal part would not be considered to be an extraneous-conductive-part as it would limit any current to 0.7mA (not even detectable with your skin) and as such, as far as i know and have read, would not need supplementary protective bonding. The usual resistance at which a part is considered not to be an extraneous-conductive-part is 23KΩ (see GN8) so there is a lot of leeway from the OP's reading.

As the person doing a PIR i would not want to recommend unnecessary work.

 

[DurhamSparky]

DONT BOND! above limit and thus you bonding will introduce a path!

 

[davemack]

Not going to bond as reading is above 25Kohms , must be 1000 houses on this estate and i have now been into 3 all have no main bond although gas pipes are main bonded, spoke to main contactor
and he's told me there is no need to bond!

Still seem's alien to me as so used to bonding water mains for the last 30 years although i can see it could indeed introduce a path, thinking i sould have tested with the tap running just out of intrest.

 

[davemack]

Maybe I've missed the post, but when you went to the main stop cock to check for the bonding clamp, was it plastic or copper than on entry?

Its plastic at entry and copper everywhere visable although must be plastic under floors

 

[SimpleSimon]

There we go. Defo don't bond you'll be introducing a potential. With a plastic pipe.

 

[davemack]

Its plastic at entry and copper everywhere visable although must be plastic under floors

Or i sould have said plastic incomer then copper after stopcock