GEC

[B&V Construction]

This is of interest as I'm working on an older Craftsman style house which has the water pipe as the only ground. House has been unevenly upgraded over the years. I am trying to persuade the homeowner to bring the entire electrical system up to code.

There are three schools of thought in the prior posts, which I'll summarize as:

1. One water pipe + one rod equals two rods (several early posters);
2. One water pipe + one rod may equal two rods under certain conditions (Fred);
3. One water pipe + one rod does not equal two rods (Wayne et al)

Position 3 is basically saying that the water pipe is irrelevant (though we recognize it may need to be bonded to the GE by code or the inspector). If you drive two rods (or one tested to <25 ohms) then the rod(s) constitute a ground electrode already.

Which position is correct?

 

[Djelite]

If the water pipe is available you must use it period thats one. The water pipe must be supplemented because its not a reliable gec by itself but you must use it thats two. A rod can be used as a supplement to the water pipe provided it has a value of 25 ohms or less if not 2 rods are needed to supplement the water piping period

 

[B&V Construction]

Side note: A well casing would be a far better ground electrode than any rod. It would surprise me if one well casing plus one rod did not constitute an acceptable earth ground.

Bret

 

[Djelite]

you can either one a ground rod is used more often. If you use a rod it has to measure 25 ohms or you must add a second rod . A concrete encase is another option it has nothing to do with the 2 rods

 

[B&V Construction]

If the water pipe is available you must use it period thats one. The water pipe must be supplemented because its not a reliable gec by itself but you must use it thats two. A rod can be used as a supplement to the water pipe provided it has a value of 25 ohms or less if not 2 rods are needed to supplement the water piping period

It sounds like you are in camp #3.

I would say "if a  metallic water pipe is available you must bond it to the ground electrode".

If you drive a rod and test it <25 ohms (or drive two rods, or as you point out if the house has a CCE) then I am not sure the rod(s) are supplementing the water pipe. At that point the rod(s) would constitute an adequate ground electrode by themselves. This would be true even if all the water piping was plastic. So if there's a metallic water pipe bonded in it's kind of just along for the ride. Right?

 

[LarryFine]

A concrete encase is another option it has nothing to do with the 2 rods

Actually, a system with an Ufer ground requires no other electrodes.

 

[Djelite]

Well I didn’t say it did only the water pipe needs to be supplemented. And a single rod needs to be supplemented by another rod if 25 ohms is not accomplished

 

[ActionDave]

It sounds like you are in camp #3.

I would say "if a  metallic water pipe is available you must bond it to the ground electrode".

If you drive a rod and test it <25 ohms (or drive two rods, or as you point out if the house has a CCE) then I am not sure the rod(s) are supplementing the water pipe. At that point the rod(s) would constitute an adequate ground electrode by themselves. This would be true even if all the water piping was plastic. So if there's a metallic water pipe bonded in it's kind of just along for the ride. Right?

You seem to be approaching this subject from a viewpoint that the rules are rooted in some sort of logic or science. They are not.

 

[B&V Construction]

You seem to be approaching this subject from a viewpoint that the rules are rooted in some sort of logic or science. They are not.

There's some sort of science... but if you start asking things like why 25 ohms? Why 8 feet? Well... maybe best to just try and understand what is required to get your work passed and do it.

I found some information from the NFPA which clarifies the logic. At first all water pipes were iron and so grounding to them worked fine. But sometimes grounds would be disconnected for one reason or another, so they added language about supplementing water pipes. Built-in redundancy supplies a margin of safety - job done, right? Then utilities began using PVC pipe, and this presented a new risk. If the water provider 'ungrounds' a customer then the redundancy is no longer present - and the customer may be unaware. This led to the most recent updates to the requirements.

So there is some logic! And camp #3 is correct. It's what I wrote above - the NFPA foresees a future in which metallic water pipes just won't be reliable grounds. Ergo the concept of supplementing the water pipe is outdated. You must install a ground electrode system which would be acceptable even if the water pipe were to become ungrounded.

Thanks all!

Bret