Bonding (bond Wire) & Spa Installation On Existing Concrete Pad - Electrical - DIY Chatroom Home Improvement Forum

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Old 11-14-2007, 03:29 AM   #1
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Bonding (bond wire) & Spa Installation on existing concrete pad

What can be done to meet safety/code requirements when installing a spa on an existing outdoor concrete patio/pad?

The concrete pad may have rebar in it. So, I'm particularly concerned with safety & if there's a way to somehow connect the #8 AWG bond wire (if rebar is present) to reduce voltage gradients. I would sincerely like to avoid jackhammering a perfectly good (newer) concrete pad to lay down an Equipotential Grid & repour concrete. Is there an alternative?

Also, does 6-3 Romex wire run thru buried pvc conduit (conduit exposed at outdoor box) meet code for connecting an outdoor spa?

The Romex wire contains 1 Red 6 AWG; 1 Black 6 AWG; 1 White 6 AWG; 1 bare 12 AWG... can the bare 12 AWG wire be used for grounding, or do I need to run 8 AWG Green wire along side the Romex to meet code?

Any help would be greatly appreciated.


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Old 11-14-2007, 12:00 PM   #2
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Well you have a dilemma in that the rebar should be bonded to the spa bonding lug.. You should check with your local codes department as to the requirement to access the rebar in the concrete supporting deck for bonding to the metal of the spa. First you have no way of knowing if the rebar itself is bonded correctly with the appropriate wire ties or other method. So it would be a guess whether bonding would even be beneficial. But a bond wire to an exposed piece couldn't hurt. It might be possible to dig under the slap and get access to the rebar.

The below are general requirements from Bulldog Spa's are pretty much similar across the country for most spa foundations. Note the concrete rebar part of the paragraph. Also note the special spa pads. These are often placed under the spa for a deck or are placed over a concrete pad. These pads are non-conductive material. And in my opinion would provide for a higher degree of protection from a voltage gradient that might be in the ground and concrete rebar. It by no means would be a way to eliminate 100% the possibility of shock. You would want it to cover the entire slab of concrete or 5 feet beyond the perimeter walls of the spa. You also would want the codes department to accept this as an alternative to bonding to the rebar in the slab if there is any rebar in the concrete deck. Either way I think the non-conductive pads are a good idea. And they look a heck of a lot better than concrete as many are decorative in design.

The whole idea of bonding the metal around a spa is to equalize the voltage potential between the different pieces of metal so that if you touch any metal or two different pieces of metal within 5 feet of the spa you will not get shocked. If a potential difference exists current can flow through you.

Spa Foundation General Guidelines: Select a structurally sound flat surface that is reasonably level to serve as your spa’s foundation. A foundation that shifts or settles may cause stress to the spa shell. The foundation that your spa rests on must have a weight bearing load capability of supporting the weight of your spa, its water, and the people using it. The maximum filled weight of a spa can be as much as 6,000 lbs (2,722 kg), plus the weight of the occupants that use the spa. If your spa’s pad is slightly sloped it will not affect the performance of the spa or its structure, however, there should be no dips, sags, or unevenness in the pad. Most patios are built to slope away from the house for drainage purposes. There should be no more than a ” (1.27cm) slope in an 8‘ (2.44m) run. Recommended flooring materials include a concrete pad, concrete pavers or bricks, pea gravel, or crushed rock (1.5” [3.81cm] or less), or a reinforced deck. Additionally, your Spa dealer should sell or recommend pre-formed spa pads. NOTE: Concrete foundations should be a minimum of 4” (10.16cm) thick and should be reinforced with either rebar or mesh. For electrical grounding purposes, the rebar or mesh should be attached to a bond wire.

Now if the concrete pad has rebar and you can get to it for bonding use a approved clamp. See here for examples.......

Hope this helped

As for romex in conduit underground to a spa ....absoluetely NO.

Romex is not rated for conduit underground as this is a classified wet location.... the conduit over time will get water in it.

You can however run it to the required disconnect that is out by the spa if it stays indoors to that disconnect. Otherwise it must be thwn individual wires or other wet rated insulation to be installed in conduit underground. And the ground must be insulated.

BTW 6/3 romex will have a #10 ground.

The branch circuit requires gfci at the panel or at the outside disconnect unless the pool has a built in gfci that is documented to satisfy this requirement of the NEC

All wiring from the disconnect to the spa must be in conduit. Usually liquid tight type. Make sure to run a insulated ground wire with the other conductors to the tub.

At the control box a provision will be made for the equipment ground.

Also there will be a bonding lug for your #8 bonding wire. A packaged spa is generally built on a common metal frame and this satisfies the bonding internally to the spa metal... other metal should be connected to the bonding lug. Verify with the installation manual.

Hope this helped


" One nice thing about the NEC articles ... you have lots of choices"


Last edited by Stubbie; 11-14-2007 at 02:37 PM.
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