No, five linear feet. i.e. take a ruler and measure 5' from the edge of the pool. That's the area you have to cover. It's kind of difficult for a person to span that distance with a body part in the water.

It looks as if the inspector missed the grid when the pool was installed. The 69kv transmission line nearby wasn't factored into the entire equation. Most residential primaries are only a few thousand volts.

I do agree, that replacing the service was goofy, If they replaced the ground rod or grounding system for the service then I wouldn't think it was goofy. You could either have aground rod or your power system would be grounded via copper water pipes.

You never mentioned what kind of piping you have for water and how the service is connected to "ground".

"Ground" is a reference, but thing can change what ground is over distance, Thunderstorms have the ability to create a gradient across the ground.

I know if a computing center whose data lines were damaged that went from wnd to end of the building over a maybe 200'. They replaced that section with fiber rather than copper to eliminate the problem.

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Originally Posted by tkrussell

Was going to edited my other best, best to add here I think.

Since a loose or broken connection or wire out on the utility can happen, so can happen, often, in buildings. For any metal , esp around a pool, to get energized to noticeable levels, is a dead giveaway to a loose or broken connection, with the pool grounding.

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Just to clarify -- while there was voltage being picked up on the handrails by a meter (around 2.5 volts), it could not be felt by humans unless touched directly on an open wound while in the pool. The only noticeable current to unbroken skin was not on metal at all, but on the wet pavers by the pool steps, if you were also touching the pool water at the same time. You did not even have to be in the pool -- you could touch wet pavers with one hand, and dip the other in the water (even while wearing shoes) and you would feel it. Does this make a difference in your assessment?

Not one bit. Resistance between body parts varies because of the type of tissue, open wounds, water which isn't pure because of the chemicals added.

A potential difference between the wet pavers existed between the pavers and the pool, so it depends on the value of the resistance, how much current flows between two points i.e. two hands. It doesn't matter if the feet have shoes on or not. An open wound, just makes the resistance less and the current larger.

We also don't know if the water is "bonded" to ground.

See:
Effects of current passing through the human body

Okay, now we're making an appointment with an agency that specializes in testing grounding around pools. Apparently they have some sort of instrumentation that measures potential or something, and if it beeps when contacting two surfaces, it's good; if it doesn't beep, uh-oh.

Just making sure I understand about the equipotential grid, KISS. You're saying that this grid would need to be placed 5 feet away from the water's edge, all around the pool? We have concrete pavers surrounding the entire pool, but much of it is narrower than 5 feet. However, the true patio area, where the spa and furniture are, is about 15 x 20 feet. Right in front of the steps, where we had felt the strongest shocks, is about 4'10", and the grass in front of that, between the pavers' edge and the fence between my property and the neighbor's, is about 3.5 feet. The steps, spa, and large patio area are the closest parts of the pool to the transmission wires, FWIW. Picture a piece of loose leaf paper. The margin line down the left side is the transmission wires. Our pool forms a backwards L near that line, with the bottom line of the L forming the shallow end leading to the steps, and the spa is a circle in the right angle formed by the L, with the patio "above" the spa. So, if you include the patio area in our pool's footprint, the whole thing forms a big rectangle. If I hazard a guess, I would say that the edge of the water by the steps is no more than 15-20 feet from being directly underneath the transmission wires.

Now that the problem is fixed, we are taking your concerns about our pool's grounding seriously, since it is so close to these high voltage sources, and who knows if something like this could happen again -- but worse.

No, the copper grid would go from near the edge of the pool, call it 0" to 5' away from the pool. 0 is impossible and 5' is impossible in places. The grid is about 1' x 1' square.

Look at it this way:

Water*GRID*GRID*GRID*NO GRID*NO GRID
**a**********b****************c*******

I'll call those areas a, b and c. If a human laid down on b and put his hand in a and his foot in c, he could conceiveably touch the GRID and NO GRID.

This isn't the same as what you have now because the NO GRID area won't be an instantaneous change in ground resistance.

When you would sit at he edge of the pool, you would be in the equipotential area and thus no shock.

When you walked out of the pool, you would be in aneqipotential area and hence no shock.

GRID to NO GRID should not give you a shock either.

I think you should be able to work on just the exposed areas to your property line. If you can go 5 feet, then do.

So the grid doesn't start at 5', but rather as close to the pool as practical and extends to 5'. In your case, it can't.

Also remember to ground the water in the pool.

I don't think the SPA poses a problem.

Make sense?

If you go here:

https://www.askmehelpdesk.com/electr...ne-270277.html

And jump through some hoops and register (free) with the NFPA, you can read the NEC handbook online. Can't search, can't print, can't copy. Just read.

Section 680 deals with pools an Hot Tubs.

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Originally Posted by KeepItSimpleStupid

No, the copper grid would go from near the edge of the pool, call it 0" to 5' away from the pool. 0 is impossible and 5' is impossible in places. The grid is about 1' x 1' square.

I think you should be able to work on just the exposed areas to your property line. If you can go 5 feet, then do.


Also remember to ground the water in the pool.


Make sense?

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Okay, so you're saying I could put one of these 1-square-foot grids only in the spot where we felt noticeable shocks (the "exposed areas"); i.e. in front of the pool steps. Perhaps, to be safe, we could also put one by the ladder at the deep end. There was actually voltage read all around the pool when the wire was down, but it could only be felt if you had a cut.

How do you ground the pool water?

I don't feel your problem was a broken ground system, I feel your ground was energised.

There are a few products mentioned in this thread:

Bonding pool water - InspectionNews - Home Inspection

The square inch requirement could be met by a bonded lighting fixture, a ladder etc.

Sporatically protecting the areas isn't going to do much good. You can sit on the edge of the pool with your feet in the water, so perimeter protection is necessary.


Voltage across some resistance is defined by ohms law as V = I * R where I is current and R is resistance.

Suppose we use a nice round number like 1 Amp (very lethal o the human body).

If R was 1 ohm, you would have 1 volt across it. If R was 1000 ohms you would have 1000 V across it, if R was 10,000 ohms you would have 10,000 V across it. What this is saying is that the lower the resistance the lower the drop. The grid lowers the resistance.

There is another formula that defined R=pl/A where p is a material property and is usually in ohm-cm, l is the length that the current is passing and A is the cross sectional area.

Thus, if you plug in the resistivity of copper, the length and the area of the circular diameter, you can compute R.

For bulk samples such as soil, it gets more complicated.

Here is some info relating to that.

Soil resistivity measurement

I was looking at the link you posted, KISS. What I'm getting (and please correct me if I'm wrong) is that since I have a metal pool ladder going into the water at the deep end, plus two underwater lights in metal housings, most likely the pool water is already grounded since the metal in contact with the water is grounded.

And, in regards to the grid, you're saying it WOULD need to run around the perimeter of the pool to protect any bathers who might sit on any part of the pavers with their feet in the water. In my case, this would involve ripping up the whole patio all around in order to install it. Correct?

Yes for your first question.

The second is just the pavers within 5' of the pool, not the entire patio.

Quote:

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Originally Posted by KeepItSimpleStupid

Yes for your first question.

The second is just the pavers within 5' of the pool, not the entire patio.

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Well, since I have pavers that abut the pool's edge all the way around, that would involve ripping up the whole perimeter. I realize that the pavers on the main part of the patio that are located beyond 5' of the edge could be left alone, but that's a relatively small area in comparison to the whole.

Yes for your first question.

The second is just the pavers within 5' of the pool, not the entire patio.