Equipotential Bonding (pool deck/coping).

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Ralph III

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Jan 27, 2018
139
Mobile, Al
Hello All,

Just FYI, we purchased our home last summer and some of the metal parts around our pool had lost their bond (one leg of ladder, diving board). I can only assume the original copper bonding wire (15-20yrs old) broke under the slab. Anyhow, I ran new #8 copper wire and re-bonded all the metal parts of the pool (step railing, ladder, diving board) in addition to all the equipment (pump, swg, etc). I also bonded it with the original copper wire.

Now, I have a question about equipotential bonding in regards to our concrete decking and coping.

1. My original plan was to encircle the entire outside of the swimming pool deck with a single #8 copper wire, which I am utilizing. I was then going to run individual pieces of #8 copper wire down each concrete slab divider and attach it to the pools aluminum coping via stainless screws and nuts. This would at least give me some perimeter bonding within the interior of the pool and areas within the concrete decking. That was the goal because there is no rebar in the concrete for bonding purposes. They only bonded the metal parts and equipment which is probably all that was required 20 yrs ago. I still plan on doing this unless you tell me otherwise.

2. I recently cut several 1ft x 1ft holes into the concrete to add lights and some water features. Anyhow, the earth underneath the concrete decking has settled about 4-5 inches. So I have an opportunity to run a single #8 copper wire around the interior of the pool or 18 to 24in within the pool side which I believe is the recommended bonding method? I could also run some concrete wire mesh but it would only be about 14in wide. I wouldn't be able to reach every point around my pool with the wire mesh but I probably could get about 80%. I think I can get about 95% with the single #8 copper wire.

After I have ran my copper wire and/or mesh, I plan on filling the voids under my decking with a mortar/sand mix to help support the deck. I will use concrete to fill the holes themselves.

Can you offer any suggestions in regards? Will the #8 copper or mesh be fine in the sand under my concrete deck or does it need to be encased within concrete?

Thanks,
Ralph
 
1) That's exactly what I'd recommend. Running a loop around the deck is sound practice.

2) Running a single #8 copper wire under the deck in the earth is a good addition to the loop outside the deck. I'd tie them together wherever possible, but at least four places around the pool. Running a wire in the expansion joints (concrete slab dividers) and connecting to both loops and the equipment would be better than a lot of pools have.

As for filling the voids under the decking, I'd look at flow-able grout or even mud jacking. Mud jacking is usually associated with raising sunken slabs, but they're very good at filling voids under slabs.
 
I agree with above. I wouldnt go too crazy with trying to cut holes everywhere but the more you can tie into the old wire or the pool the better. If you can fit the wire into the expansion joint that would be good too. the main thing is to have the metal pool accessories tied in and the pool itself in a few spots 4 being the least. The old bond wire is still doing something so adding to it is a good thing in this case. U have to weigh the fact you have sunken earth under the slab, any expansion joint you could now cut around the pool would make slab settle into a valley shape, ive seen that done where they cut a ring around the deck tucked the wire in and caulked it, has to be solid underneath tho for this
 
Thanks for the replies and glad to know I am on the right track. For clarity sake.

1. I have some wire mesh and #8 copper wire so I think I will use both under the concrete deck. Yes, I am tying everything together including the old copper wire, everywhere I can.

2. I will be cutting 1ft x 1ft holes into the concrete deck about every 10ft. I will run a short #8 wire at each of these cutouts and connect the outside loop to the inside loop. The outside loop is one continuous #8 copper wire that goes back to the equipment pad. The inside loop however will be made up of probably 6 sections. So I will run a piece of wire/mesh and then run another piece of wire/mesh in forming a type loop. All of that will be tied to the outside loop.

3. As noted, I will also run a #8 copper wire down each expansion joint. That will connect the outside loop to the pools coping. I had planned on routing down the 1 x 4in expansion boards and filling with caulking. I'm not sure if I will be able to connect it anywhere to the inside loop. Maybe I will try to do so in a few areas.

That is my plan anyhow.

Thanks,
Ralph
 
Ok, so I came across a definitive NEC diagram on Mike Holts website, so I may adjust a few things.

Instead of running the #8 copper wire under my concrete deck, I may instead score the surface of my concrete deck and then install the #8 copper wire within the groove created. I will then cover it with a grout. This will be better because I can reach 100 percent around my pool. I would only be able to cover about 80-90 percent if I ran it under my deck.

Number (5) of the diagram seems to suggest that I can do this? If someone can confirm this that would be great.

Thanks,
RalphPool Bonding.jpg
 
The actual article number for Equipotential Bonding is 680-26 ;

"(5) The required conductor shall be secured within or under the perimeter surface 100 mm to 150 mm (4 in. to 6 in.) below the subgrade."

Depending on how you read that, it seems line it's saying that the conductor has to be 4" to 6" below the surface (I think subgrade is misused), so to meet the letter of the law (so the speak), you'd be cutting completely through your deck. Also, you need to make sure to use grout (conductive) and not caulking (electrically insulating).

Having typed that, I think either approach would be ok, so if you'd rather make a saw cut around the pool and embed the wire in it, that would be acceptable.
 
Just be careful if u make a saw cut to embed the bond wire. It would then become an expansion joint and would be the weak point of slab. If ita hollow underneath u might have it sink down the road I've seen it happen and pretty dramatic too if it has room to sink on both sides makes a valley
 
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