Earth bonding

[teecee90]

Can anyone advise on the following please:

My main incoming water pipe appears to be double earth bonded. There is an earth strap on the vertical pipe with a secondary earth wire running from the first to a second strap on the horizontal section. Is the second one on the horizontal section necessary? If so, can it be moved to the vertical section so both are on the same section of pipe?

I ask because I want to put a pressure reduction valve on the horizontal section. Thanks

 

[Darkwood]

Welcome to the forum teecee 90 .

I've let this into the main forum for a quick response while we wait for Admin' to come online and give you a DIY status at which point your thread will be relocated. Note! this won't affect your posts and replies here... thanks.

 

[davesparks]

What is hiding under that bit of lagging? I can just see the end of a compression fitting, if this is something which is insulation gone section if pipe from the other then it may explain the two bonding connections

 

[teecee90]

Some sort of scale inhibitor

 

[Richard Burns]

Ideally even though the scale inhibitor appears to be steel there should be continuity of bonding from the main incomer across the inhibitor.
The first bonding clamp could be moved to the section above the tap as shown by the green arrow.
If the main bonding runs as I have pictured the green and yellow line and then goes back to the first clamp and the pipework indicated by the red arrow is made of plastic then the clamp should be safe to remove.
However testing should be undertaken to ensure this is the case.

 

[teecee90]

Ideally even though the scale inhibitor appears to be steel there should be continuity of bonding from the main incomer across the inhibitor.
The first bonding clamp could be moved to the section above the tap as shown by the green arrow.
If the main bonding runs as I have pictured the green and yellow line and then goes back to the first clamp and the pipework indicated by the red arrow is made of plastic then the clamp should be safe to remove.
However testing should be undertaken to ensure this is the case.
View attachment 30026

Thanks for the reply. Yes, the main bonding run is exactly as you have shown with the green and yellow line with a secondary cable that goes from this clamp back to the first clamp. The pipe coming up through the floor is indeed blue plastic. So are you saying I should be able to remove the first clamp completely rather than moving it?

Cheers.

 

[telectrix]

remove the lower clamp. the bond on the vertical section is the necessary one.

 

[Leesparkykent]

remove the lower clamp. the bond on the vertical section is the necessary one.

Do you mean remove the higher clamp?

 

[Leesparkykent]

Some sort of scale inhibitor

View attachment 30024

Is the pipe below the stopcock that's covered in lagging plastic?

 

[teecee90]

Is the pipe below the stopcock that's covered in lagging plastic?

Yes it is.

 

[Leesparkykent]

Yes it is.

Chances are it may not even be extraneous as the incoming pipe is plastic. There is a possibility though if the copper part of the installation re-enters the ground again, etc. The only way to establish this though to be 100% is by carrying out a test.

 

[teecee90]

Chances are it may not even be extraneous as the incoming pipe is plastic. There is a possibility though if the copper part of the installation re-enters the ground again, etc. The only way to establish this though to be 100% is by carrying out a test.

Is the test something I can carry out myself? It seems a bit OTT to get an electrician in just to move an earth clamp, but I obviously don't want to do anything that will cause a safety problem.

 

[telectrix]

Do you mean remove the higher clamp?

no.it's the pipe entering the property that needs bonding.

 

[Leesparkykent]

Is the test something I can carry out myself? It seems a bit OTT to get an electrician in just to move an earth clamp, but I obviously don't want to do anything that will cause a safety problem.

You would normally use an insulation resistance test instrument set on a low range and carry out a test between the suspect part and the known earth/MET to determine the resistance. It would not be deemed extraneous if above 23Kohms. Unfortunately most people who are not electricians will not possess such test equipment.

 

[Leesparkykent]

no.it's the pipe entering the property that needs bonding.

That what I mean...so you would keep the clamp on the horizontal section of pipe (lower clamp) and remove the one on the vertical section of pipe (higher clamp) :stuart:

 

[teecee90]

You would normally use an insulation resistance test instrument set on a low range and carry out a test between the suspect part and the known earth/MET to determine the resistance. It would not be deemed extraneous if above 23Kohms. Unfortunately most people who are not electricians will not possess such test equipment.

I guess that's a no then. The only thing I have is a multimeter. Oh well, best leave things alone and look for somewhere else to fit the PRV.

 

[Leesparkykent]

I guess that's a no then. The only thing I have is a multimeter. Oh well, best leave things alone and look for somewhere else to fit the PRV.

Before you fit the pressure reducing valve have you tried slowly turning the stopcock towards the off position until you get the required reduced pressure?

 

[teecee90]

Before you fit the pressure reducing valve have you tried slowly turning the stopcock off until you get the required reduced pressure?

Yes, that didn't work. To reduce the pressure enough the flow is far too slow.

 

[Leesparkykent]

Yes, that didn't work. To reduce the pressure enough the flow is far too slow.

Does the pipe dart off through the wall just after the higher clamp or carry on up the wall?

 

[telectrix]

I guess that's a no then. The only thing I have is a multimeter. Oh well, best leave things alone and look for somewhere else to fit the PRV.

diss. the cable from 1 clamp and test with your multimeter between the 2 clamps. if thr reading is close to zero ohms, then you can assume that the 2 points are electrically connected via the copper pipe.

 

[teecee90]

Does the pipe dart off through the wall just after the higher clamp or carry on up the wall?

The pipe is in the garage. It carries on up the wall just past the ceiling joists and then branches off into the wall - presumably which takes it into the space between upstairs floor and downstairs ceiling.

 

[Richard Burns]

Pay attention to Tel's posts they are useful.
Since there is bonding in place it may be assumed that it is there purposely, i.e. someone checked at some point that bonding was required.

Because your main incoming pipe is plastic it cannot introduce a significant earth potential therefore removing the clamp on the horizontal section and its connecting wire would mean that there was now just the main bonding connection on the vertical section within 600 mm of the incoming water as is recommended (even though it may not be required because of the plastic pipe incoming), if the rest of the metal pipework can introduce a potential then it is also bonded so there is no risk.

If you do as Tel says with the continuity this should be sufficient to be safe.

The requirement for bonding across the inhibitor would be if someone removed the inhibitor there may be different potentials on the pipe work either side of it and this could cause a shock to the person removing the inhibitor.
However if someone is doing this then they should put temporary clamps across anyway, so the risk is minimised.
Since the section from the inihibitor down to the plastic pipe is floating (in relation to potential) it should not cause a risk anyway.

I would suggest removing the lower clamp, leaving the upper clamp connected back to the consumer unit and just fit the PRV in place.

If you are worried about this then move the lower clamp down to above the top of the tap using a single piece of 10mm² cable to connect back to the upper clamp and there is no danger at all.

 

[teecee90]

diss. the cable from 1 clamp and test with your multimeter between the 2 clamps. if thr reading is close to zero ohms, then you can assume that the 2 points are electrically connected via the copper pipe.

With the joining cable disconnected the resistance is around 0.3 Ohms, with the cable connected it is around 0.2 Ohms..... so not much of a difference. I assume this means I can safely remove the lower clamp on the horizontal section.

 

[Richard Burns]

Yep take it away, it is not doing much there.