Based on the '05 NEC, 680.26(C) asks us to install an Equipotential Bonding Grid under the pool and along the sides of the pool plus extend out 36" out from the inside wall of the pool under the deck. There is a TIA that says if the pool is a non-conductive type such as a polymer or a vinyl liner pool it does not have to be under the pool or along the sides of the pool. My question is: When we are talking about this non=conductive pool with no grid under the pool or along the sides of the pool are we still required to have a 36" grid under the deck or walking surface? My understanding is that the reason for the grid is the fact that people set on the edge of the pool with their feet in the water etc.

TIA 05-2

That is the way I understand it.

I think this is why the issues are so ... confusing:

You're tempted to think: A plastic pool is, more or less, insulated from the ground around it. Why should I have to have a grounding network if the deck is isolated in this way? It seems backwards .... and to serve no purpose.

Yet, that insulation is the very reason we want the grid. Let's look at it again.

Assume that, for some reason, either the deck or the water become energized. With a plastic liner acting as an insulator, you have just allowed a voltage difference to exist. Voltage difference = shock hazard.

Bond the two together, and the two are kept at the same potential ... no more shocks. Just as important, with a good bond, the fault is more likely to trip the breaker. In this arrange, it is JUST AS IMPORTANT that the 'water be bonded' as it is to have that grid.

While this approach doesn't solve every issue, it is hoped to lessen the risk. It appears this whole situation came about the moment we started using those plastic drop-in pool forms; before then, it appears that there was enough conductivity through the pool walls to prevent this from being an issue in most cases. The prevalence of plastic piping has probably also contributed to this 'voltage gradient' issue.

I wouldn't be at all surprised if the day comes when we look at deliberately treating the water for conductivity - making it sure it's very conductive - as well. We might even require the use of conductive pipe.

Remember .... it's not just a question of pool equipment. Indeed, I have one customer who, for religious reasons, deliberately constructed a pool without directly connected filters, pumps, or metal piping. Yet, there are still the lights in the pool room, the radio / sound system, and all manner of possible introduced electrical sources. Even though that particular room has no receptacles - there's no way to prevent someone from running a cord.

Greg- I expected to hear from you and you didn't let me down. You and I agree that the grid would still be needed.
Reno- Thanks for the information and I think you were agreeing with Greg and I but you never said so in so many words

My personal opinion is you can't have too many bonding paths.
John is right, these "stray voltage" problems in pools and spas started when we got away from conductive pool shells, plumbing and decking materials.
For that matter the loss of a totally metallic water utility system took away the city wide equipotential grid that existed when the original electrical systems were designed.

I know in my own little world, I don't pour any concrete that is not bonded. My whole house, driveway, pool and spa is one big Ufer and everything is bonded to everything.

This does get back to the 2008 "bond the water" rule too.
That only requires a 2" long metal pipe nipple right now but I bet they make a better bond rule before this is over.
You can have conductive materials in fiberglass and that might be the real answer but it won't do anything for the million that are already out there.

If I recall, a properly chlorinated pool is already a fairly good conductor of electricity, and comparable to the conductivity of blood.
Or simply getting in or out of the pool from the deck, too. Lots of ways for the human body to become the circuit connecting the equipotential plane to the water.

You're right .. I was in agreement. I just wanted to 'step back' a bit, and put the issue in context - mainly for the education of others who might read this thread.

Steve, chlorinated water may be, might not be, etc. We need to look further.

The religious pool I described, for religious reasons, is NOT allowed to use treated water. Naturally, since the design is at least 3000 years old, they have some reason to believe that their rules have stood the test of time.

Another customer has a pool that is NOT chlorinated, at all. They treat with ozone.

Pool rules can also come into play with ornamental ponds, which may have plants and fish in them. Something to consider.

Absolute pure water - 0.055 µS/cm (20MOhms/cm)
Distilled water - 0.5 µS/cm (2MOhm/cm)
Mountain water - 1.0 µS/cm (1MOhm/cm)
Most drinking water sources - 500 to 800 µS/cm (1.4kOhm/cm)
Sea water - 56 mS/cm (18 Ohms/cm)
Max for potable water - 1055 µS/cm (1kOhm/cm)

Couldn't find the #s for typical pool water.

It depends on how many people peed in it.

If I get some spare time I will set up my conductivity experiment again. It was a white bucket with two one foot #10 probes in contact with water and 8" apart in series with a 60w light bulb.

I did this a while ago and was surprised at how little salt it took to get the bulb to glow. I now have the ability to test for total dissolved salts content. I can't find my results but I did plot current and voltage drop for various solutions.

I have inspected many pools over the last 10 years as an AHJ and I have never seen stray voltage a problem with pools that have rebar in the gunite or pools with metal sides. The only time I have seen stray voltage problems is with the fiberglass pools. There have been at least 2-5 times I have heard about these problems. The one pool had 15-30 votlts between the handrail into the pool and the concrete deck. Another pool had over 50 volts from the deck to the wet niche light.

Harold (or others), What is the best way to check for these stray voltages?
I have done the meter trick with a probe in the water etc.
My inground liner pool (20+- yrs) has checked out fine to me.
Just looking for perhaps a more true measuring meens.
I think in the spring I will do the pool water bond thing to it.

Although it is not the best way to test it, actually getting a tingle while you are in the pool is usually what prompts the call.
If I was going to "probe" the water I would clip my lead to a foot or so of aluminum foil and drop that in the pool, then measure to anything you can touch. I would still be skeptical of any reading I got with a digital meter without a couple hundred k shunt.
You may already have some bonding going on if you have a regular pump (not double insulated). If you have a heater there is plenty of bonding going on.
Probably the most effective bonding would be a bonded metal ladder in the water.