Bonding rebar in pool retaining wall

TKR

Gold Supporter
May 21, 2019
60
Central NC
I had a discussion with our inspector about the steel rebar in our pool's retaining wall being tied into the bonding loop. (pictures below).

He noticed that I had a stub-out piece of 8g copper coming out of the each section of the wall. It is clamped to the rebar (vertical in the footing wire-tied to a horizontal bond beam). I told him I am going to attach those wires to the bonding wire loop under the pavers later. He said he would not have required me to put this in but had no issues with it.

My read of the code is that is not needed, as well, but I do think it will help equalizing the potential in the narrow deck area.

Any thoughts on this?

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Our overall design is this with a retaining wall on 3 sides of the pool.............
side elevation zoom1.png

The wall cross section is like this with vertical steel rebar in the footing, tied to a horizontal rebar in a bond beam running the perimeter.........
excavation detail2 .png
IMG_1204.JPG
 

JamesW

TFP Expert
Mar 2, 2011
18,406
I believe that the rebar and aluminum fence/rail are required to be bonded since they are within 5 feet of the pool.

I would also suggest that you install a conductive metal grid (copper or steel) around the perimeter of the pool.
 
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VirtualChris

Member
Aug 16, 2019
10
California
I think 5 feet is in Canada, and in the US I believe it's 10 feet (any metal within this distance). Anyways, this equipotential bonding for pool perimeters and parts should be connected to any/all metal around the pool. So, if you have a metal handrail, light niches, pool pumps, pool heater, inline sacrificial anode, tiki torches, etc...all should be connected together on that loop. Here is an example article for more information: Taking the Mystery Out of Equipotential Bonding Requirements for Swimming Pools - IAEI Magazine
 
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TKR

Gold Supporter
May 21, 2019
60
Central NC
Thanks for the replies. I will hook it in (along with railing)

suggest that you install a conductive metal grid (copper or steel) around the perimeter of the pool.
I was planning on an 8g wire loop under the pavers. It will probably be embedded in gravel rather than paver base.

A grid seems more effective than a wire overall. Does the grid have particular advantage because of 100% gravel fill?
 

JamesW

TFP Expert
Mar 2, 2011
18,406
A grid gives you better coverage and reduces the likelihood of feeling stray currents.

There are several threads where the owner feels small shocks when standing on the deck and touching the water.

In most of these cases, there is no grid in the deck.

The risk is small, but if it happens to you, you're going to wish that you installed a grid.

One current thread has the owner ripping out the deck to install a grid. It's been going on for 6 years. Very frustrating.

 
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TKR

Gold Supporter
May 21, 2019
60
Central NC
I read up a bit on this copper grid and found that the upcoming 2020 NEC has added copper grid as an alternative means to bonding the deck surface. The 8g copper ring remains as the other alternative in the 2020 code.

So... the current code specifies an 8g conductor, placed 18-24 inches from the pool edge. The copper grid runs out 36" from edge of the pool? Even though it seems a better option, the grid does not meet current code wording. Are inspectors passing installation of the copper grid?
 

JamesW

TFP Expert
Mar 2, 2011
18,406
You still need the #8 bare copper wire, but you add the metal grid in the deck and connect it to the bond wire.
 
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jimmythegreek

TFP Expert
Bronze Supporter
In The Industry
Aug 10, 2017
2,132
Morris Cnty NJ
My buddy dealt with this once. An inspector in a ritzy town known for busting chops failed a bond inspection. The bond was to code for a paver deck install. 4 equal points and all metal and rails bonded on a steel wall pool. They town was going by an older nec code and an addendum to their pool code. Owner was forced to buy 2 grand worth of pre made copper grid and run it outside the walls all around pool and tie it all into the bonding. This was under the pavers below the sand top of sub base. That town has since gone away with the requirement. With pavers the ring is to be in contact with moisture which could conduct static and stray voltage. I personally have never dealt with any issues on any pool with a paver patio. I have dealt with it on a concrete deck and the water ended up with no bonding as the light niche rotted out its lug from chlorine. I would just tie it all together with a single loop or maybe even a double loop if you wanna go crazy and call it good. The mesh is expensive and just not needed if its all properly connected. And btw most inspectors would want the rebar bonded and the railing for sure they fall within min distance code it doesnt matter what the item is
 
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TKR

Gold Supporter
May 21, 2019
60
Central NC
You still need the #8 bare copper wire, but you add the metal grid in the deck and connect it to the bond wire.
Makes sense given the NEC code situation.
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I am planning to use a synthetic paver base, like Gator Base.
1583293017003.png

The copper ring wire would have to go well below the geo-fabric in the picture below. I suppose the copper grid could go in a sand layer above or below the paver base panel. This panel is recommended for pool decks but I wonder if it would interfere the bonding unless the copper grid was in the upper sand layer that is in contact with the pavers?

gator base.png
 

TKR

Gold Supporter
May 21, 2019
60
Central NC
Owner was forced to buy 2 grand worth of pre made copper grid and run it outside the walls all around pool
With pavers the ring is to be in contact with moisture which could conduct static and stray voltage.
I would just tie it all together with a single loop or maybe even a double loop if you wanna go crazy and call it good.
Thanks Jimmy. Its sounds like bonding the wall rebar worked out for the best.

Given how narrow my patio area is, an extra loop or two of copper 8g wire would give me almost as much contact as the grid.

The moisture aspect is interesting to me. Will pea gravel backfill offer good contact to the wire?
 

JamesW

TFP Expert
Mar 2, 2011
18,406
I think that the risk is low with pavers.

Using the grid is extra cautious.

Most likely, you won't have a problem.

However, if there is any stray current felt, then you're going to wish that you installed the grid.
 
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jimmythegreek

TFP Expert
Bronze Supporter
In The Industry
Aug 10, 2017
2,132
Morris Cnty NJ
Pavers usually sit on sand and it's almost always damp underneath. Needs a few days of dry and sun to dry out. The idea is the moisture coming up thru the sun base can carry thru to anything moist above it especially concrete. Its actually like a sponge and sucks water. The bond ring equalizes anything to the rest of the pool and its area. Pavers are by far the safest decking choice and I've never personally dealt with a bond issue or ever heard of one with pavers.
I've used the gator base last year. In your situation I wouldnt. It's an extra expense you dont need. The idea is to save excavation and removal of soil costs plus the cost and labor of sun base. You already have all that because of the pool install. You dont need sand to lay the pavers on. All you do is get fine stone like grit and screed that and lay the pavers on it. Many crews use open graded base nowadays with the whole base being 3/4 clean stone. In above grade like your install its ideal. If you are worries about where the bedding sand will go you just put down geotextile first and then screed and lay pavers. When your ready I'll post some tricks we use for screeding. Only use concrete sand btw nothing else must be course sand never mason sand or stone dust
 
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