Multiple Underground Water Pipes

[wwhitney]

250.52(A)(1) tells us a "metal underground water pipe in direct contact with the earth for 3.0 m (10 ft) or more" is a grounding electrode, and 250.50 says it needs to be part of the grounding electrode system.

Does that mean that when a building is connected to multiple such metal underground water pipes, each one needs to be connected to as a grounding electrode? E.g. a building supplied by two metal water laterals, one for domestic water and one for fire sprinklers (separate systems inside the building).

How about when the different underground water pipes are connected within the building via a complete metal water piping system? E.g. metal water service at one end of a house, metal interior water piping to the other end of the house, metal water piping exits the building and goes underground for at least 10' to supply an outbuilding.

Cheers, Wayne

 

[Elect117]

It needs to be connect/bonded once, so long as it enters the building at any point. Whether it qualifies as an electrode is a bonus. Two different requirements. 250.104 vs 250.50. Any metal piping system would need to be bonded where not electrically continuous and how / where it is bonded kind of depends.

You wouldn't need more than one water pipe to qualify as an electrode. You would typically follow that up with another type. Hence the required if present but not required to be installed. The difference between 1-3 and 4-8.

 

[wwhitney]

You wouldn't need more than one water pipe to qualify as an electrode.

But if more than one metal water pipe is present, doesn't 250.50 require that we use each one as an electrode?

Cheers, Wayne

 

[Elect117]

But if more than one metal water pipe is present, doesn't 250.50 require that we use each one as an electrode?

Cheers, Wayne

I would say yes in very few circumstances. For example, if your city has more than one water utility and you have one of each feeding your property. I feel the wording 250.50(A), where it says "permitted", allows you to bond it even if it might have counted as an electrode. Like each electrode present must be bonded but you don't have to say it is an electrode.

Like you put in two ground rods for a temp service in a parking lot and then bury it after the temp service is done. It is present. You wouldn't need to go find it and bond it to the electrode system. Some things would still need to be bonded, like metal underground piping systems, building steel, etc.

I take it to mean that the requirement of 250.50 is more focused on making a good electrode system and 250.104 is focused on metal systems that can become energized or have differences in potential.

 

[MyCleveland]

It needs to be connect/bonded once, so long as it enters the building at any point. Whether it qualifies as an electrode is a bonus. Two different requirements. 250.104 vs 250.50. Any metal piping system would need to be bonded where not electrically continuous and how / where it is bonded kind of depends.

You wouldn't need more than one water pipe to qualify as an electrode. You would typically follow that up with another type. Hence the required if present but not required to be installed. The difference between 1-3 and 4-8.

There is a Nfpa code that states you may not use sprinkler piping as an electrode.
Like many things…I do not recall the doc number.

 

[jaggedben]

But if more than one metal water pipe is present, doesn't 250.50 require that we use each one as an electrode?

I would say yes, but additonal GEC/bonding jumper connections would only be required if the multiple underground pipes are not otherwise electrically continuous. In my experience I think it has almost always been a moot point.

 

[wwhitney]

I would say yes, but additonal GEC/bonding jumper connections would only be required if the multiple underground pipes are not otherwise electrically continuous. In my experience I think it has almost always been a moot point.

Seems to me each electrode is just the underground segment of metal water pipe. And 250.62(C)(1) says "Interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building shall not be used as a conductor to interconnect electrodes of the grounding electrode system." So the separate metal underground water pipe electrodes would need to be interconnected with a bonding jumper or GEC.

Cheers, Wayne

 

[jaggedben]

Seems to me each electrode is just the underground segment of metal water pipe. ...

I disagree. The code has never stated that clearly and everyone acts like it's not true. If you drive a 10ft rod 8ft into the ground, are the exposed 2ft not part of the electrode and are you therefore not allowed to connect the GEC there? What if it's a pipe that's 20ft tall? Everyone bonds GECs to electrodes above ground and it's unstated where the electrode ends.

 

[Greentagger]

250.50.
If it qualifies as an electrode it is required to be used.
The only exception is if multiple CCEs are present, only one is required to be used.

 

[Fred B]

Being a "Grounding Electrode" or not the Metal water pipes must be bonded (250.104). Now the debate has been and likely to continue is what is "likely to become energized", seeming to be somewhat subjective and at the discretion of the inspector.

There is a Nfpa code that states you may not use sprinkler piping as an electrode.
Like many things…I do not recall the doc number.

Now as to a sprinkler system, was in a facility recently and at some point someone (assuming the maintenance personnel) strapped MC cables in multiple locations to the sprinkler pipe. Would such now mean it is likely to become energized? Again "Bonding" and "Electrode" are two different things.

I disagree. The code has never stated that clearly and everyone acts like it's not true. If you drive a 10ft rod 8ft into the ground, are the exposed 2ft not part of the electrode and are you therefore not allowed to connect the GEC there? What if it's a pipe that's 20ft tall? Everyone bonds GECs to electrodes above ground and it's unstated where the electrode ends.

Can't agree. It appears clearly stated. The Part above grade does not count as an Electrode, note multiple references below, AFA connecting to the above grade portion it is permitted but "with protection".
250.53(A)(4) .....unless the aboveground end and the grounding electrode conductor attachment are protected against physical damage as specified in 250.10. Ground clamps or other fittings exposed to physical damage shall be enclosed in metal, wood, or equivalent protective covering.

250.52(A)
(1) Metal Underground Water Pipe.
A metal underground water pipe in direct contact with the earth for 3.0 m (10 ft) or more.......
(2) Metal In-ground Support Structure(s)
One or more metal in-ground support structure(s) in direct contact with the earth vertically for 3.0 m (10 ft) or more,........
3) Concrete-Encased Electrode.
........Metal components shall be encased by at least 50 mm (2 in.) of concrete and shall be located horizontally within that portion of a concrete foundation or footing that is in direct contact with the earth or ........
(4) Ground Ring.
A ground ring encircling the building or structure, in direct contact with the earth, .........
Etc.

250.53(A)(4) .........The upper end of the electrode shall be flush with or below ground level .......

 

[wwhitney]

I disagree. The code has never stated that clearly and everyone acts like it's not true. If you drive a 10ft rod 8ft into the ground, are the exposed 2ft not part of the electrode and are you therefore not allowed to connect the GEC there?

Well, the difference is that the ground rod is not consistently referred to as "underground ground rod" so there's no restriction that only the underground portion of the ground rod is the electrode. There's just a rule that at least 8' has to be in contact with the earth.

But let me suspend that particular assertion for the moment. 250.62(C)(1) still makes it clear that above ground metal water piping more than 5' inside of the building shall not be used to connect electrodes, and hence is not part of the electrode. So if you have a continuous section of metal water pipe that is underground, then >10' inside the building, then underground, that's two different electrodes, and you need to connect a GEC/bonding jumper to each of them. [Unless 250.62(C)(1) exception applies, that lets you rely on interior metal water piping more than 5' inside the building to interconnect electrodes.]

Everyone bonds GECs to electrodes above ground and it's unstated where the electrode ends.

Maybe, maybe not, but 250.62(C)(1) provides a bound on where it ends--it is definitely no longer an electrode once it's 5' inside the building (when the exception doesn't apply.)

Cheers, Wayne

 

[Dennis Alwon]

Well, the difference is that the ground rod is not consistently referred to as "underground ground rod" so there's no restriction that only the underground portion of the ground rod is the electrode. There's just a rule that at least 8' has to be in contact with the earth.

But let me suspend that particular assertion for the moment. 250.62(C)(1) still makes it clear that above ground metal water piping more than 5' inside of the building shall not be used to connect electrodes, and hence is not part of the electrode. So if you have a continuous section of metal water pipe that is underground, then >10' inside the building, then underground, that's two different electrodes, and you need to connect a GEC/bonding jumper to each of them. [Unless 250.62(C)(1) exception applies, that lets you rely on interior metal water piping more than 5' inside the building to interconnect electrodes.]

Imo, that is one electrode not 2 simply because it is the same pipe. Go a step further and, as you stated, the 10' inside the building ( I am assuming there is 10' after the first 5') doesn't have to be bonded separately because it is part of the electrode and is already connected to an electrode.

 

[infinity]

Without wording stating otherwise if there are two water pipes that qualify as electrodes entering the building then both must be used because they are both present. The fact that they could be connected right outside of the building should matter but it doesn’t.

 

[wwhitney]

Imo, that is one electrode not 2 simply because it is the same pipe.

Going with that idea for the moment, would you say that if the interior piping were 5' metal, 5' plastic, 5' metal, with the exterior and underground piping metal at both ends, now it is 2 electrodes?

If so, seems to me that 250.62(C)(1) says that even if that middlemost 5' of interior piping is metal, we can't use it to interconnect electrodes. While it doesn't explictly say so, we should assume that middlemost 5' of interior piping could be changed to plastic at any time. So even if it is metal, we should treat this scenario as two different electrodes.

Cheers, Wayne

 

[jaggedben]

...

If so, seems to me that 250.62(C)(1) says that even if that middlemost 5' of interior piping is metal, we can't use it to interconnect electrodes. While it doesn't explictly say so, we should assume that middlemost 5' of interior piping could be changed to plastic at any time. So even if it is metal, we should treat this scenario as two different electrodes.
...

Except that two metal pipes connected by plastic are clearly not 'a metal pipe' (singular) whereas a continuous metal pipe in the ground at both ends may be a singular pipe and electrode.

In my opinion the 5ft rule only applies to the interconnection of other electrodes to the pipe. I don't even accept that a GEC connection to the pipe needs to land in that first 5ft. (I mean in practice I do that because it's very commonly understood that way, but I don't accept that a strict reading of the code requires it.)

 

[Dennis Alwon]

Going with that idea for the moment, would you say that if the interior piping were 5' metal, 5' plastic, 5' metal, with the exterior and underground piping metal at both ends, now it is 2 electrodes?

If so, seems to me that 250.62(C)(1) says that even if that middlemost 5' of interior piping is metal, we can't use it to interconnect electrodes. While it doesn't explictly say so, we should assume that middlemost 5' of interior piping could be changed to plastic at any time. So even if it is metal, we should treat this scenario as two different electrodes.

Cheers, Wayne

So you are going with a "what if" scenario. It used to be that we cannot look at what-ifs but it is clear that the NEC certainly has rules that protect the "what-ifs"

If there is plastic then IMO you have 2 electrodes but honestly we will not get an answer to this issue on this forum. You would have to write a proposal and see what they think. Probably not a common occurrence but I see your point.

 

[Fred B]

250.53(D) Metal Underground Water Pipe.
If used as a grounding electrode, metal underground water pipe shall meet the requirements of 250.53(D)(1) and (D)(2).

250.53(D)(2) Supplemental Electrode Required.
A metal underground water pipe shall be supplemented by an additional electrode of a type specified in 250.52(A)(2) through (A)(8)

2 water pipes still only count as 1 electrode, as water pipe is not included in 250.52(A)(2) through (A)(8) for a required supplemental electrode. You could have 20 or more Water Pipes coming into the building it still only counts once but all still must be bonded.

250.50 Grounding Electrode System.
All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together.....
250.104(A)(1) General.
Metal water piping system(s) installed in or attached to a building or structure shall be bonded to any of the following: .......

 

[wwhitney]

So you are going with a "what if" scenario. It used to be that we cannot look at what-ifs but it is clear that the NEC certainly has rules that protect the "what-ifs"

Not so much a what if scenario as arguing that the electrode definitely does not extend more that 5' inside the building. So if the electrode for one section of underground pipe does not overlap with the electrode for another underground section, you have two electrodes.

Let me flip this around: suppose I managed to get a 25' ground rod, and I bent it into a U shape with two 9' vertical segments and a 7' horizontal segment, and I drive/bury it so that both vertical segments are at least 8' in the ground. Does that count as two ground rods, or just one? Seems like it is obviously two.

So likewise, if you have two separate underground water pipe segments (separated by >10' of interior water piping) you have two separate electrodes.

Cheers, Wayne

 

[jaggedben]

....

Let me flip this around: suppose I managed to get a 25' ground rod, and I bent it into a U shape with two 9' vertical segments and a 7' horizontal segment, and I drive/bury it so that both vertical segments are at least 8' in the ground. Does that count as two ground rods, or just one? Seems like it is obviously two.

...

Seems like it is obviously one.

Interestingly, I cannot bend the rod in a U shape and drive it only 4' into the ground on both ends and claim it to be a qualifying electrode, because of the 'driven to a depth of not less than 8ft' language. But the water pipe section is not so specific, leaving open the possibility that my u-shaped water pipe could have 5ft of contact with earth on both sides (in any direction) and still qualify.

 

[jaggedben]

Not so much a what if scenario as arguing that the electrode definitely does not extend more that 5' inside the building. ...

Note the language in 250.52(A)(1) "electrically continuous ... to the points of connection of the GEC", and how the sentence structure implies that's all part of the electrode. FWIW, I believe that this language predates the "5ft rule". Now consider whether anything in the 5ft rule language directly contradicts this implication.