Equipotential Bonding

[mwemaxxowner]

I'm working on building us a stock tank hot tub/pool. Based on what I can find in the NEC (not that I'm incredibly familiar with it) this pool doesn't necessarily qualify to need bonding. It's well below 42" and I think whether it would be considered portable is a grey area. It could well be drained and moved but we don't plan to ever do so. I'm not sure why having water levels of less than 42" would protect us in the event of an electrical fault vs 43".

However I'd like to have it all bonded anyway. The pump will be a double insulated intex pump but the heater is not double insulated. Everything will be powered from gfci receptacles or breakers.

My biggest question here, as I read about bonding above ground pools with steel panels, it reads that if all panels are bolted together, the pool walls need only be bonded in one location as it all ties together. I interpret that to mean this galvanized stock tank need only be bonded with one lug to bond the entire tank.

My next question, since there is no liner, if the tank is properly bonded, since it is in constant contact with the water the water itself is also bonded, no?

If not I will purchase an in line water bonding kit or one of the kits that replaces the drain plug in the pump.

Once it is all set up, I will test the bonding at various points around the pool and to the pool equipment per Mike Holt's instructional videos, but I hope to get it all right the first time.

This tank will be on a corner of the concrete patio that is around our IGP, so I assume I should, or at least that it will be good to, bond this to the bonding grid for the patio and the big pool. I can access that fairly easily near the location for this tub.

I realize that my questions did not address bonding the heater or anything else and that will be done, I'm just curious whether, in this situation, bonding the tank also bonds the water so I don't need to order anything else.

 

[JamesW]

I interpret that to mean this galvanized stock tank need only be bonded with one lug to bond the entire tank.

My next question, since there is no liner, if the tank is properly bonded, since it is in constant contact with the water the water itself is also bonded, no?

I suspect that 1 bond would suffice, but I would suggest bonding at a minimum of four (4) points uniformly spaced around the perimeter of the pool to be safe.

I think that a bonded metal wall in contact with the water would qualify as a water bond.

Electrical Bonding - Further Reading

www.troublefreepool.com

Note that different jurisdictions have different specific rules that have to be followed.

Also, note that there is a lot of ambiguity in the code and different inspectors can interpret the code differently.

So, verify all plans before beginning and after installation with a qualified electrician, local inspector or other qualified expert professional.

 

[mwemaxxowner]

I have read the above link, but continue to go back and review it and other resources in my spare time and as I work out this project. Thank you for your assistance!

 

[mwemaxxowner]

Little sneak peek of where it is after finishing up for today! I've used some old scrap carpet padding to insulate it (saved it after we put laminate down in the house). I have 6 layers around it. It's not a great deal of R value, but it seems to be much more than every other stock tank hot tub build I've found. Once I'm done, I may try to fill most of the cabinet with blow in insulation or something if it seems to not hold temps well enough. I want to build a cover from 4" of xps foam.

 

[ajw22]

@RDspaguy what do you think?

 

[RDspaguy]

@RDspaguy what do you think?

I try not to think whenever possible. It usually gets me in trouble.
Bonding is more about the equipment than safety, and is meant to keep all points of the system at the same potential. Bonding just the tub defeats the purpose. You need to bond the tub to the heater to the pump(s) to the whatever else is in contact with the water (ladders, handrails, etc.) that is conductive or electrical. A bond is not the same as a ground, and bonded equipment must still be grounded back to the panel even though the bond connects to a ground.
Portable spas are excluded not because they are portable, but because they are fiberglass and do not have conductive contact with the dirt, concrete, etc. The equipment in them is still bonded, just not to the fiberglass tub or earth.

 

[mwemaxxowner]

I try not to think whenever possible. It usually gets me in trouble.
Bonding is more about the equipment than safety, and is meant to keep all points of the system at the same potential. Bonding just the tub defeats the purpose. You need to bond the tub to the heater to the pump(s) to the whatever else is in contact with the water (ladders, handrails, etc.) that is conductive or electrical. A bond is not the same as a ground, and bonded equipment must still be grounded back to the panel even though the bond connects to a ground.
Portable spas are excluded not because they are portable, but because they are fiberglass and do not have conductive contact with the dirt, concrete, etc. The equipment in them is still bonded, just not to the fiberglass tub or earth.

I understand that.

I'm not sure how to bond the double insulated intex pump, as there is no bonding lug and it is all plastic. Aside from that, I'm going to bond everything just as you've said. My plan was not only to bond the water or the water and the tub, that was just the part I was specifically unsure of .