Bond wire - Fiberglass pool

McLovitz

Member
Electrical novice here but, as a homeowner, I'm stuck between my electrician and town electrical inspector while installing an inground fiberglass pool in your backyard. I came here hoping for an expert view to sort through the disagreement.

In short, we failed our bond wire inspection yesterday as the town said the bond wire has to be 4-6" below grade per code. Per our contractor, we are going to pour 3" or so of concrete on top of the wire (as a bond beam to secure the pool) and then above that, paver stones will sit on the top level that are 2.25" thick (and in between there will be a paver base) so the bond wire will clearly be at least 4-6 inches below the final grade once the final grade is set. However, the town inspector still insists we have to bury the bond wire 4-6" below the dirt before pouring concrete. Our contractor insists this is less safe as the bond wire will be too far below the final grade once we go 4-6" below dirt then add concrete, then paver base, then paver. So he is pushing back but in the meantime our project is held up while they fight over what is code. Again, I'm a novice and I see the 4" to 6" is measured from "subgrade" per the code. I'm not sure what is meant by "subgrade."

Any thoughts are much appreciated.
 

Dennis Alwon

Moderator
Staff member
No one seems to know what sub grade is but IMO, the subgrade is the dirt below the concrete. I have to agree with the inspector. BTW, it doesn't matter what the electricians state-- unless they can show that it is not safe 4-6" down then they don't have a prayer to stand on.

IMO, you want the wire into the top not ontop as the wire is trying to make contact with any voltage gradient that may exist. It seems it would be better below the dirt-- just my opinion.
 

McLovitz

Member
Thanks for the quick replies. I like the idea of 2 bond wires. Heck, I'll tell the contractor that I will buy the wire and that way we're covered both ways.
 

mopowr steve

Senior Member
I thought it was clearly stated that if concrete was poured with reinforcing steel (rebar or mesh) that is your Equipotential bonding grid. If there was a lack thereof then a Equipotential bond wire needs installed 4”-6” below grade (soil).
 

Little Bill

Moderator
Staff member
Inspectors here differ on the requirement. Some will allow the bond wire to lay on top of the gravel base under pavers or concrete. Others want it 4-6" below the gravel base (and dirt if the gravel isn't 4-6" deep enough). I have to agree that subgrade is what is below the final grade, kind of like a subfloor is below finished floor. So, IMO, the wire should be 4-6" below the subgrade.
 

david

Senior Member
I'm not sure what is meant by "subgrade."

Any thoughts are much appreciated.
Generally speaking sub-grade is a construction term, the earth or fill that is compacted to support a load such as a slab, pavers or most commonly a road

Most pools have a perimeter surface such as grass a slab or pavers

Without constructing something you do not have sub-grade but in the case of the perimeter surface needing bonded when the surface is soil and grass the only thing that makes sense is to place the bond 4 to 6 inches below “grade”

With the term sub grade and a surface being constructed your inspector would be correct
 

McLovitz

Member
So here's the latest on our dilemma. We had another electrician come out today who agreed with the inspector and is willing to bury the wire below the soil 4"-6" and finish the job.

While the other electrician was at our house, our contractor got in touch with the state DCA. He tells me the guy he spoke with said it would be best to pour the 3" of concrete around the pool and place the copper wire in the paver base, under the paver stone. I'm not sure how that gets us 4"-6" below the paver grade, but we're now trying to get our contractor, the town electrical inspector and DCA on the phone to coordinate.
 

Dennis Alwon

Moderator
Staff member
I think the advice to do both is probably the best since one is in and the inspector wants another. That should cover you.
 

McLovitz

Member
I think that makes the most sense to me. Contractor expressed a concern that two copper wires could be too much. Is that a real concern?
 

PaulMmn

Senior Member
Contractor said 2 wires is too much? Too much what? Cost? Too much 'bonding?' Too much work to install?? If he's worried about different potential on each wire, drop connections between them every 20 feet or so! That's going to be one well-bonded pool!
 

Mystic Pools

Senior Member
On a new build about 8 years ago, an inspector requested the 4"-6" requirement, which was fine, but he made us use garden stakes to secure the wire to keep it within the 18"-24" distance. THAT was a new one.This was a gunite pool BTW.

On a different job, same inspector, he questioned the GFCI requirement. I had a different interpretation of the code. He told me to call the state and see what they had to say. I did, and I relayed the information to the inspector, which was in my favor, and it passed. He was a fair gentlemen. Sadly he passed away.

So, yes, it was good idea to contact the state and get your definitive answer.
Running 2 wires is not really costly, but is certainly ok.

A poster mentioned the steel rebar or the steel wire mesh is sufficient for the EBG. I've had inspectors tell me no and others tell me yes. It's all about the way they interpret the code. I never know what to expect unless I've dealt with the same inspector on previous jobs.

Don't forget the water bond!!!
 

brian john

Senior Member
So we are told concrete in contact with the Earth is one of the better ground electrodes available, then why isn't a concrete walkway around a pool with steel mesh a better way to achieve the end goal than a #8 AWG CU conductor?
 

Dennis Alwon

Moderator
Staff member
So we are told concrete in contact with the Earth is one of the better ground electrodes available, then why isn't a concrete walkway around a pool with steel mesh a better way to achieve the end goal than a #8 AWG CU conductor?
Because it isn't down deep enough where there tends to be more moisture. That would be my guess. BTW, good to hear from you again. It's been awhile
 

Mystic Pools

Senior Member
I just want to mention that we always run the bond wire around the pool perimeter despite the use of wire mesh or any rebar used in a concrete pour. I'd rather have it in place.


Setting any steel outside of a concrete pour in the earth would corrode and lose the bonding it was intended for.
 

kwired

Electron manager
No one seems to know what sub grade is but IMO, the subgrade is the dirt below the concrete. I have to agree with the inspector. BTW, it doesn't matter what the electricians state-- unless they can show that it is not safe 4-6" down then they don't have a prayer to stand on.

IMO, you want the wire into the top not ontop as the wire is trying to make contact with any voltage gradient that may exist. It seems it would be better below the dirt-- just my opinion.
We are not trying to make a grounding electrode with this perimeter bonding we are trying to assure there is no voltage gradients at the surface of the pool perimeter - to which a pool user would have potential to come into contact with different voltages between the pool and/or points along the perimeter.

That said a voltage gradient very well can exist as you move away from the pool and any outer edge of what perimeter bonding metals are existing. Perimeter that is poured concrete with any metal reinforcement or simply bonding wire embedded will likely be a better surface at reducing voltage gradients than a simple bonding wire in the earth near the edge of the pool. The fact it is around the pool probably increases the chance there is moisture present in the sub soil which helps the effectiveness of any perimeter bonding method period. If the pool is seldom used that may decrease chances some though.

ETA: if you put the bonding wire too deep you will have too much voltage gradient between your bonging wire and the surface and users of the pool will be subjected to that voltage.
 
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Dennis Alwon

Moderator
Staff member
We are not trying to make a grounding electrode with this perimeter bonding we are trying to assure there is no voltage gradients at the surface of the pool perimeter - to which a pool user would have potential to come into contact with different voltages between the pool and/or points along the perimeter.

That said a voltage gradient very well can exist as you move away from the pool and any outer edge of what perimeter bonding metals are existing. Perimeter that is poured concrete with any metal reinforcement or simply bonding wire embedded will likely be a better surface at reducing voltage gradients than a simple bonding wire in the earth near the edge of the pool. The fact it is around the pool probably increases the chance there is moisture present in the sub soil which helps the effectiveness of any perimeter bonding method period. If the pool is seldom used that may decrease chances some though.
I know it isn't an electrode but if there is voltage in the soil do you not thing being in the soil would be better than in the concrete where there is likely to more contact.
 

kwired

Electron manager
I know it isn't an electrode but if there is voltage in the soil do you not thing being in the soil would be better than in the concrete where there is likely to more contact.
The goal is equipotential at user accessible surfaces, we don't even care if the entire pool and other bonded components are sitting there at 1000 volts to ground, just so there is no potential that users can come across.

The soil is likely to be at "earth potential", but like I said we are more concerned about potential at the surface and this bonding is installed for the purpose of equalizing that and is bonded to the rest of the pool components so they are all the same potential.

ETA: the fact that we bring an equipment grounding conductor to pool equipment makes it possible for everything bonded to it, which is also connected to the grounded service conductor, which is also connected to the utility company MGN (in a majority of cases) to have voltage drop of the grounded service conductor or even voltage drop of the utility MGN to be imposed on the pool and all bonded components - which will result in a voltage between those items and "earth".
 
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