Bonding in Bathroom

[JohnW2]

As you say, the regs do not prescribe a test of whether or not something is an extraneous-c-p, but they do define a test of the adequacy of supplementary bonding, and I thought you had been known to suggest that this test can also be used to determine whether supplementary bonding is required (i.e. whether a part qualifies as 'extraneous').

That is true.

The problem with that one is that "Ia" can be 30mA for an RCD or, say, 160A for a B32 - so that the maximum permissible resistance can be 1667Ω or 0.3125Ω !!

Why is that a problem? ... That is why supplementary bonding may be omitted when RCDs are fitted. ... However, should the resistance be between 1667 and 23,000 (or 46,000) then supplementary bonding would still be required.

The 'problem' (if there is one) is that the regs do not seem to explicitly recognise that 'passing' your ">23kΩ" (which, as you say, is arbitrary) is necessarily an acceptable means of demonstrating that something is not an extraneous-c-p (and therefore does not require SB). In other words, the 'problem' is probably that the regs do not define 'liable to introduce a potential' in a manner similar to that which your test attempts to do.

You will see that BAS has somewhat thrown a spanner into the works, by illustrating that the water in a short 'plastic interruption' is probably enough to result in a failure of your ">23kΩ test".

Kind Regards, John

 

[EFLImpudence]

The 'problem' (if there is one) is that the regs do not seem to explicitly recognise that 'passing' your ">23kΩ" (which, as you say, is arbitrary) is necessarily an acceptable means of demonstrating that something is not an extraneous-c-p (and therefore does not require SB).

... but it is recognised by most as the test to use (apart from those who prefer 46k&#937.
What would you suggest as a better alternative?

Also, it does not just apply to SB.

In other words, the 'problem' is probably that the regs do not define 'liable to introduce a potential' in a manner similar to that which your test attempts to do.

They do not but other potential has to be considered as well.

You will see that BAS has somewhat thrown a spanner into the works, by illustrating that the water in a short 'plastic interruption' is probably enough to result in a failure of your ">23kΩ test".

It is not an unknown spanner, is it?
I do not understand your quandary about 'failing' the test.
It merely means that bonding is required - main and/or supplementary.
You may not even know the interruption is there so would have tested anyway.

So, 1cm. @ 115kΩ /m = 1,150Ω - well below the/my test - will require bonding in the absence of RCDs.


It all seems quite straight forward to me; am I missing something?

 

[JohnW2]

The 'problem' (if there is one) is that the regs do not seem to explicitly recognise that 'passing' your ">23kΩ" (which, as you say, is arbitrary) is necessarily an acceptable means of demonstrating that something is not an extraneous-c-p (and therefore does not require SB).

... but it is recognised by most as the test to use (apart from those who prefer 46k&#937. What would you suggest as a better alternative? Also, it does not just apply to SB.

I'm not suggesting that there is anything unreasonable about it, or than we need an 'alternative' - but I do think that the regs ought to define their criteria for what constitutes "being liable to introduce a potential (usually earth potential)". The regs clearly indicate that bonding (main or SB) is only required for extraneous-c-ps, but it is not really very satisfactory that the criteria for that be "what is recognised by most", rather than criteria actually specified in the regs, is it?

You will see that BAS has somewhat thrown a spanner into the works, by illustrating that the water in a short 'plastic interruption' is probably enough to result in a failure of your ">23kΩ test".

It is not an unknown spanner, is it? I do not understand your quandary about 'failing' the test. It merely means that bonding is required - main and/or supplementary.

Perhaps I misunderstood, because I thought that you previously indicated that you were not concerned about the conductivity of water in the pipes and therefore agreed that SB would not be required downstream of a 'plastic interruption'.

So, 1cm. @ 115kΩ /m = 1,150Ω - well below the/my test - will require bonding in the absence of RCDs.

Indeed.

It all seems quite straight forward to me; am I missing something?

Only that it appears that I may have misunderstood you. As above, I thought you had indicated that you did not think/believe that the water within a 'plastic interruption' would give rise to the need for SB....

Are you thinking of the conductivity of water in the pipes?

Not really, just don't know the situation for certain.

Kind Regards, John

 

[EFLImpudence]

Are you thinking of the conductivity of water in the pipes?

Not really, just don't know the situation for certain.

In reply to "Are you thinking of the conductivity of water in the pipes?" I said "Not really, just don't know the situation for certain".

Which was in response to:

2. Should my mains cold water have bonding after the plastic fitting?
3. Should the hot water have bonding after the plastic fitting?

Can't tell from here or by looking at it.

Measurements need to be taken to determine if bonding is required.

I'm sorry if it was not clear but I was trying to indicate that the situation would have to be inspected.
Instead of "not really" perhaps I should have written "not particularly".

 

[JohnW2]

In reply to "Are you thinking of the conductivity of water in the pipes?" I said "Not really, just don't know the situation for certain". ... I'm sorry if it was not clear but I was trying to indicate that the situation would have to be inspected. ... Instead of "not really" perhaps I should have written "not particularly".

There clearly has been a little confusion. However, I would have said that, given what you are now saying, neither "not really" nor "not particularly" really represented your view, and, AIUI, "yes" would probably have been a fairer response, and would have avoided the confusion I experienced ...

... as I went on to say back then, AFAICS if one were not entertaining ("thinking of") the possibility that the conductivity of the water might be a relevant issue, it would surely be as obvious that a pipe downstream of a 'plastic interruption' was not an extraneous-c-p as it is obvious that a pipe emerging out of the ground is an extraneous-c-p - in both cases without the need for any measurements.

Kind Regards, John

 

[EFLImpudence]

There clearly has been a little confusion. However, I would have said that, given what you are now saying, neither "not really" nor "not particularly" really represented your view, and, AIUI, "yes" would probably have been a fairer response, and would have avoided the confusion I experienced ...

Apologies again if I was confusing but I think I was quite clear in saying that nothing could be determined from here.

... as I went on to say back then, AFAICS if one were not entertaining ("thinking of") the possibility that the conductivity of the water might be a relevant issue, it would surely be as obvious that a pipe downstream of a 'plastic interruption' was not an extraneous-c-p as it is obvious that a pipe emerging out of the ground is an extraneous-c-p - in both cases without the need for any measurements.

I was not entertaining anything at all - we cannot tell.

Don't forget that the thread is about bonding in a bathroom so the fact that the OP said there was one plastic joint gives no insight into what else there may be between the supply and the bathroom.


My and the first reply.

2. Should my mains cold water have bonding after the plastic fitting?
3. Should the hot water have bonding after the plastic fitting?

Can't tell from here or by looking at it.

Measurements need to be taken to determine if bonding is required.

 

[JohnW2]

Apologies again if I was confusing but I think I was quite clear in saying that nothing could be determined from here.

You were clear in saying that. It is I who was trying to tempt you into making assumptions based on what we were told.

I realise that it's what the OP asked about, but I suppose one thing which has been confusing me a bit is that we have been concentrating on the copper pipework downstream of the plastic fittings, and whether it does, or does not, need bonding. As I understand it, the copper pipes enter the bathroom in copper (prior to the plastic fittings) and it is surely those pipes (before the fittings) which either will or will not require SB (quite possibly not, due to very low impedance path to MET). Having either done, or not done, that bonding, as appropriate, there surely would not be a requirement to bond (or additionally bond) the same pipe run further downstream, even if it were all copper, let alone when it has plastic fittings in it? ... or am I missing something?

Kind Regards, John