10mm bonding to copper and plastic install.

[Robo]

Im going to be doing a consumer unit change. There is already 10mm boding to gas and water pipes. However the customer has has some renovation work done to the plumbing.

So it starts off copper and then goes to plastic and then goes back to copper. Am i right in thinking i need to take a seperate 10mm bond to each copper pipe?? or??

 

[Engineer54]

Test the water pipe first to see if it meets the requirement of bonding, under 22k ohms as i remember!! If it does, i would be more inclined to bond between the 2 sections of copper pipe, rather than take a second bond back to the MET!!!

 

[FAA Greenie]

Yup, you should bridge the gap between the copper piping with 10mm bonding if the plumber has not already done so. Many may argue that (Possibly correctly) you that the existing install is not your problem as long as you can test with good results so long as you provide a 16mm earth to the new CU, but are you really going to leave your client without adequate protection? (remember you can IR test as much as you want between plastic and it will all be good). You need to do a continuity test between the MET and the furthest copper pipe to be safe.

One question i have not seen on this forum yet, plumbers responsibilities regarding earthing/bonding. The DO have them!!!

 

[Robo]

The current consumerunt is 16th and is probs one of the last installed. It has 25mm tails and 16mm earth. The 10mm bond goes to gas and then to water pipe? I would norm run a seperate for each. Theres been a fair amount of plumbing work carried out. so im unsure where is plastic and where is metal. It seems to be copper coming down the walls to rads but fair amout of plastic elsewhere (ie roof space). Then its plastic coming into bathroom which goes to copper for bath sink toilet etc. There could be a number of breaks. what do u prepose i do??? and is it ok to link gas to water??

 

[Robo]

Do a r2 tes with a wander lead engineer 54?? the reading should be under 22k ohms? please see reply below. Thanks mate

 

[Deleted member 9648]

You only need to main bond at the point of entry OR to the nearest section of copper to the point of entry. What happens to the pipework beyond that point (such as plastic inserts) matters not. There is no requirement to ensure continuity beyond the point of bonding as the hazard (and reason for main bonding) comes from externally and has been dealt with by bonding at the point of entry.It is perfectly permissible to link gas and water with one main bond conductor,but it must be continuous,not cut at the clamp.
FAA Greenies post is not correct and shows a lack of understanding of the reason for main bonding.



Edit.....the 22k figure is just to establish whether the incoming water pipe is an extraneous conductive part,it may not be if the incoming service is plastic.....test between a copper section and a conductive part and if the reading is >22k you can assume the service is not extraneous and will not need main bonding. In practice this can be difficult due to parallel paths within the installation.
As you already have a bonding conductor in place just use it, and ensure the bond is connected on the first section of copper on the consumers side of the stopcock. As previously stated you can ignore the pipework beyond that point,there is no requirement,or need for it to be electrically continuous.

 

[Robo]

The 10mm bond is continous from the gas to the water. The incoming water main is metal.

Sorry to be a pain in the butt but im not very clear on the testing part. Could you please help.
o
Long lead continuity test from the bonding incoming main to main MET should be under 0.05 ohms.?

do i need to then to a long lead test which should be from the incoming water main to any other suspect copper work. if ist open circuit im ok? if i get a reading it needs to be under 1667ohms?

23k reading is flying about. How do i do this.

Iv read numerous previous posts and getting very confuzzled on the testng procedures and results. Somebody simplify this. Thanks

 

[Deleted member 9648]

Main bond at the point of entry on the consumers side of the stopcock if the incoming water main is metallic...in other words clamp onto copper just above the stopcock.....forget the rest of the pipework beyond the main bond,it is irrelevent.
You can either continuity test from the MET to the point of bonding using a wander lead and as you state,the reading should be <0.05ohms, or it is also permissible to confirm the bonding visually if it is not hidden.

I would suggest you read up on the purpose of main bonding....of which there are a number of threads on here explaining it.....in particular understand the definitions of extraneous conductive parts and conductive parts as found in the definitions section of the BRB.....There is more confusion and inaccurate posts on this subject than any other on here,always because vast numbers of electricians dont understand what main bonding is for. Usually they think it is to "earth the pipes"....or "stop them coming live"....neither of which is true.

The high resistance reading you mention is simply to find if an incoming service is actually an extraneous conductive part....a water service may be plastic and as such may not introduce an earth potential,in which case bonding may be omitted....the test is to confirm that.....as your water main is incoming metallic it will be extraneous and will definately require bonding.

 

[Engineer54]

If there are several areas that have been replaced by plastic pipe then it's a pointless exercise. If it is just a short section that has been replaced, then i would be inclined to bridge bond.

 

[Deleted member 9648]

If there are several areas that have been replaced by plastic pipe then it's a pointless exercise. If it is just a short section that has been replaced, then i would be inclined to bridge bond.

Why?.......Do you not understand main bonding either?

 

[Engineer54]

I understand it, maybe better than most.... So tell me, if you could see the two ends of the short plastic replacement pipe, you wouldn't bother bridge bonding, is that what your saying??

 

[Deleted member 9648]

There is no reason to bridge,the reason to bond comes from outside of the property...by bonding at the point of entry that reason has been dealt with.

 

[Engineer54]

Hmmm.... i think i'll stick to my way of doing things!! This is a common problem these days, where plumbers, rather than keeping to the original installation material, will quite happily bung in a bit of plastic willy nilly, without a second thought, and often leave the bonding cable flapping about in thin air!!!

 

[morph]

the external service is bonded , the rest is irelevent, the risk from the external service has been dealt with , the rest of the copper in the house is not a risk ! should we bond everything metal ? no is the answer

 

[Engineer54]

Really, ....and how exactly would you know that?? By that statement you wouldn't even take the time to test the copper pipework after that short bit of plastic, to be sure. ...And Yes i would still cross bond bathroom/special locations, as i don't have the blind faith as most in relying on an RCD device.