Bonding & earthing

[david3456]

On re-doing the bathroom a thought occurs about bonding.

The main water supply pipe, bonded to the supply, runs up the bathroom wall to the tank. Taps and radiators are equipotentialed. Connection between the supply and the other pipes is then incidental.

The supply pipe was previously inside a box but is being moved to a corner where it doesn't need a box for cosmetics.

Can the arrangement be left as is, ought the pipe be boxed again or could it be linked?

Or to insert a length of plastic pipe between kitchen (where the supply rises) and bathroom?

 

[JohnW2]

I'm not sure that I understand your concern. Provided that the water supply pipe has the required main bonding close to where it enters the property, it does not matter where they pipe subsequently goes, what other pipework it is connected to or whether it is enclosed or not. ... or am I missing something?

Kind Regards, John

 

[david3456]

I'm not sure that I understand your concern. Provided that the water supply pipe has the required main bonding close to where it enters the property, it does not matter where they pipe subsequently goes, what other pipework it is connected to or whether it is enclosed or not. ... or am I missing something?

Hmmm. I was wondering whether I was missing something. Equipotentialed pipework can theoretically reach some voltage other than earth. On that basis, the supply and other pipes could be different.

 

[JohnW2]

Hmmm. I was wondering whether I was missing something. Equipotentialed pipework can theoretically reach some voltage other than earth. On that basis, the supply and other pipes could be different.

If by "equipotentialled" you mean Supplementary Bonded, then that should be connected to the installation's earthing system, which is the same place the supply pipe is main bonded to. The whole point of Main Bonding of a supply pipe is to ensure that it cannot be at a significantly different potential from that of the installation's 'earthing' system.

Furthermore, wherever there is any scope for an electrical potential to be introduced into pipework (e.g. from CH pumps or valves, immersion heaters, boilers etc.), there will again be earthing of that part (hence also pipework) via the electrical connections.

In practice of course, provided there is no plastic pipework, all the metal pipework (both water and gas) in a house is effectively joined electrically via the plumbing connections.

Kind Regards, John

 

[bernardgreen]

Is supplementary bonding always connected to an "earthed" item.

Isn't it possible that the supplementary bonding in a bathroom has no connection to an item that also has a connection to the "earth" ( CPC ) of the installation ?

 

[JohnW2]

Is supplementary bonding always connected to an "earthed" item. Isn't it possible that the supplementary bonding in a bathroom has no connection to an item that also has a connection to the "earth" ( CPC ) of the installation ?

Yes, Supplementary Bonding is required to be connected to the CPCs of circuits within the location (room).

Plumbers' "cross-bonding" (joining pipes together without any connection to the installation's CPCs) is neither necessary nor recognised by the regs.

Kind Regards, John

 

[david3456]

In practice of course, provided there is no plastic pipework, all the metal pipework (both water and gas) in a house is effectively joined electrically via the plumbing connections.

Quite. The pipes are obviously "earthed" by some means and I'm not concerned about safety, only about interpreting the rules. So you appear to be saying that any bonding that exists between pipework ought to run back to earth in a more visible manner?

 

[JohnW2]

Quite. The pipes are obviously "earthed" by some means and I'm not concerned about safety, only about interpreting the rules. So you appear to be saying that any bonding that exists between pipework ought to run back to earth in a more visible manner?

As far as the regulations are concerned, if all the circuits within the bathroom are RCD protected, then there is almost certainly not a requirement to have Supplementary Bonding at all. However, if there were a requirement for SB (e.g. because of absence of RCD protection), then that would have to be connected (by cable) to the CPCs ('earths') of all circuits in the room.

Kind Regards, John

 

[EFLImpudence]

Is supplementary bonding always connected to an "earthed" item.

Yes, that is why it may require supplementary (additional) bonding.

Isn't it possible that the supplementary bonding in a bathroom has no connection to an item that also has a connection to the "earth" ( CPC ) of the installation ?

Not only possible but desirable.

If you meant to write the two negatives then:
Supplementary Bonding should NOT be connected to an item which has NO connection to CPCs.

 

[JohnW2]

Is supplementary bonding always connected to an "earthed" item.

Yes, that is why it may require supplementary (additional) bonding.

I think there is probably scope for considerable confusion here.probably due to the varying use of language. I think that bernard was asking whether pipes etc. joined together in the name of SB (which, as I think you're implying, would only be necessary if they had paths to earth) also necessarily have to be connected to the CPCs of the electrical installation - and the answer is (as you may be saying!) 'yes'.

Isn't it possible that the supplementary bonding in a bathroom has no connection to an item that also has a connection to the "earth" ( CPC ) of the installation ?

Not only possible but desirable. ... If you meant to write the two negatives then: Supplementary Bonding should NOT be connected to an item which has NO connection to CPCs.

... and I suspect that lot might cause even more confusion

Kind Regards, John