Earth Bonding and plastic water pipes

[Barney12]

Hi All

 

there has been a useful conversation over the merits of plastic pipe (HEP2O, Speedfit etc) in the following thread: Linky

 

which triggered another question in my mind:

 

What are the requirements for earth bonding where an install is primarily plastic?

When and where should it be used? 

Edited January 27, 2017 by Nickfromwales
Added search tags :-)

[Jeremy Harris]

In general no requirement for earth bonding with an all plastic pipe installation, but there are some areas where if you have metal pipe sections and electrical equipment (like a water heater) you still require main bonding.

 

There's a useful paper that Hepworth sent out, and that is now buried on their website about this.  It wasn't written by them, but by an IEE chap, but it's pretty much chapter and verse on what should and should not be done.  It also gives the reasoning behind the decisions, which is helpful.

 

Plastic pipe earth bonding requirements

[joe90]

Yet another brilliant example of the wealth of knowledge this forum brings to us all, I have bookmarked it and filed away. Thanks JSH.

[Steptoe]

You only need to  bond the water if the continuity between the incoming water supply and the Main Earth Terminal is under 22K ohm, most plumbers put a short section of copper directly after the stopcock in case it is required.

It doesn't really matter whether the install is plastic or copper .

[Steptoe]

3 hours ago, JSHarris said:

In general no requirement for earth bonding with an all plastic pipe installation, but there are some areas where if you have metal pipe sections and electrical equipment (like a water heater) you still require main bonding.

 

There's a useful paper that Hepworth sent out, and that is now buried on their website about this.  It wasn't written by them, but by an IEE chap, but it's pretty much chapter and verse on what should and should not be done.  It also gives the reasoning behind the decisions, which is helpful.

 

Plastic pipe earth bonding requirements

That's a very old document, its superseded now with the use of ADS, supplementary bonding is now all but obsolete in (all but a very few special cases ) installations carried out since 2008, 

[Jeremy Harris]

2 hours ago, joe90 said:

Yet another brilliant example of the wealth of knowledge this forum brings to us all, I have bookmarked it and filed away. Thanks JSH.

 

Thanks, Joe,

 

TBH, I dug around for a definitive paper (and by that I mean trustworthy, as in written by someone with the right credentials, relevant competence and ideally manufacturer support as well) when I decided to switch from copper to plastic in our build.

 

Be careful to look at the exceptions to the general rule that bonding isn't required with plastic pipe, as there are areas where you do still need to bond metal parts of the system, depending on whether there is electrical equipment connected to sections of metal pipe, and the class of those items of equipment.  It's all covered in that paper fairly clearly, I found, with the general rule that short lengths of copper pipe, such as those used to neatly terminate pipework in a cabinet, don't generally need bonding unless they are over 0.5m in length, or unless they are connected to electrical equipment.  Because we have, like a few mainly plastic pipe systems, some areas where there is copper pipe connected to plastic pipe in several locations, there was still a mandatory requirement to bond some things, like the copper pipes connected to the Sunamp PV, those connected to the Stiebel Eltron water heater  and those connected to the boiling water tap.

 

There's no requirement to earth bond a plastic main connected to plastic piping, and so all our cold water stuff from the incoming supply and all the filtration etc, didn't need bonding anywhere, as the only electrical connection was an SELV timer, powered by a double insulated power supply, and even that was in a plastic housing, with composite (non-conductive) filtration tanks. 

[Steptoe]

As I said in the post above

The only definitive way of knowing if the pipework requires a main bond is to measure it with a proper continuity tester.

If your electrical system has been designed properly, supplementary (cross) bonding almost certainly should NOT be put in place.