water.ground

[bravo421]

A friend recently purchased a home with both a well and city water coming into the house. Should both be used as a water ground? If so, would an individual line to both be required, or just a continuous run from one to the next? What if one incoming water line was plastic? In that situation, I would assume clamp to one as it enters and then to the closest cold line of the one with the incoming plastic?

 

[Dennis Alwon]

All electrodes must be used so if the well line has metal for 10' or more then it must be used as an electrode. You can run one continuous line to the first electrode then use bonding jumpers to the others.

 

[augie47]

250.52 states a metallic water line in contact with the earth for 10 ft or more is a grounding electrode. If you have two such systems, you should connect to both.
IMO, you could do so with two separate grounding electrode conductors, or you could connect between them as long as you did so within the 1st 5 ft of where the pipe enters the structure.
If either is plastic underground, then you would only need to bond to the interior metallic pipe system if it is metallic and that could be done at any point

 

[infinity]

What if both lines were copper and already connected/piped together inside of the house?

 

[Rewire]

What if both lines were copper and already connected/piped together inside of the house?

The electrode is outside the house so each sysytem would be an electrode even if bonded inside. I read the code as stating ALL electrodes where available.

 

[infinity]

The electrode is outside the house so each sysytem would be an electrode even if bonded inside. I read the code as stating ALL electrodes where available.

So I'm guessing that if the connection to one is within 5' of the connection to the other then only one GEC is required.

 

[bravo421]

Thanks all ! Thought the same, just wanted a confirmation.

 

[bravo421]

So I'm guessing that if the connection to one is within 5' of the connection to the other then only one GEC is required.

why would 2 separate water systems be connected together?

 

[infinity]

why would 2 separate water systems be connected together?

So you could use either one by turning a few valves. Kind of lends itself to the question of why have both in the first place.

 

[George Stolz]

I'm no plumber, but I can imagine the city would have a problem with a resident pumping water into the city lines. I've only seen them separate, and the well water considered non-potable.

If the piping doesn't interconnect, there are two electrodes that have to be connected to. The only exceptions for multiple electrodes of the same type is in 250.52(C).

 

[bravo421]

So you could use either one by turning a few valves. Kind of lends itself to the question of why have both in the first place.

in the situation I was referring to, the well fed the lawn faucets, and the city supply took care of the house. I've seen this before in older subdivisions that had wells and then the city brought a line through years down the road.

 

[jumper]

I'm no plumber, but I can imagine the city would have a problem with a resident pumping water into the city lines. I've only seen them separate, and the well water considered non-potable.

Most, if not all, municipalities install back flow prevention devices to avoid this problem.

 

[infinity]

I find this confusing because if the well system used for lawn sprinklers is not connected in any way to the interior piping is it then considered a present electrode? 250.53(D)(1) seems to lean towards some connection to the interior piping to be an electrode.

 

[Dennis Alwon]

I was assuming two separate systems as they have here. One is for landscape water and the other for domestic use.

 

[K8MHZ]

I was assuming two separate systems as they have here. One is for landscape water and the other for domestic use.

A couple years ago we did a re-mod that had a well for the outside/sprinkler water and city water for the rest. The two systems were not connected through the water pipe. EC ran a bond wire to the well pump pipe and a very knowledgeble inspector made the EC remove it, saying the ground loop it would cause was more of a hazard than any hazard mitigated by the separate bond wire. Electrically, the pump and metal pipe were already connected to the panel ground through the NMS grounding conductor supplying power to the pump.

I never got a detailed answer, but Don the Inspector knows the NEC inside and out and this was one case where the EC just did as he was told, as odd as it sounded.

 

[Dennis Alwon]

I don't understand the ground loop. How is this any different from any other electrode?

 

[K8MHZ]

I don't understand the ground loop. How is this any different from any other electrode?

Ya got me!

But I'll bet that if I remember to ask him next time I see him he will provide me a sketch with 27 circles and arrows and paragraph on the back describing what each one was about.

But here is my plain old guess.

The well pump was bonded with a grounding connector sized to the circuit that was providing power to it. The well pump was solid iron bolted directly to the well. So the 'electrode' was bonded to the pump with nuts and bolts.

With the bonding cable from the well back to the panel there would be three paths for a ground fault to take.

1) The bonding conductor that the inspector made go away.

2) The grounding conductor in the cable that feeds the pump.

3) Through the earth to the other grounding electrodes and their conductors. In this case, both the well and the city water supply were excellent electrodes due to their size and continuous contact with wet earth.

Three parallel conductors of different impedances certainly does make a case for ground loops, but so doesn't two?

I am sure as per the NEC he was right, I just don't know exactly why.....

 

[kwired]

Ya got me!

But I'll bet that if I remember to ask him next time I see him he will provide me a sketch with 27 circles and arrows and paragraph on the back describing what each one was about.

But here is my plain old guess.

The well pump was bonded with a grounding connector sized to the circuit that was providing power to it. The well pump was solid iron bolted directly to the well. So the 'electrode' was bonded to the pump with nuts and bolts.

With the bonding cable from the well back to the panel there would be three paths for a ground fault to take.

1) The bonding conductor that the inspector made go away.

2) The grounding conductor in the cable that feeds the pump.

3) Through the earth to the other grounding electrodes and their conductors. In this case, both the well and the city water supply were excellent electrodes due to their size and continuous contact with wet earth.

Three parallel conductors of different impedances certainly does make a case for ground loops, but so doesn't two?

I am sure as per the NEC he was right, I just don't know exactly why.....

And you could drive hunderds of ground rods connected to the EGC of hundreds of branch circuits all in the same facility, all NEC acceptable but none NEC required, and still have ground loops. I say if anything was a design issue but not a NEC violation.

 

[infinity]

And you could drive hunderds of ground rods connected to the EGC of hundreds of branch circuits all in the same facility, all NEC acceptable but none NEC required, and still have ground loops. I say if anything was a design issue but not a NEC violation.

I agree, I don't see how you can "over" ground a system. A normally installed sytem has multiple ground loops.