Water Depth of Storable Swimming Pool

..."We offer above ground pools in three different wall heights, 48”, 52”, and 54”. The idea here is that the taller your pool wall, the deeper your water can end up being. This does not mean however, that if you purchase a 52” wall that you’ll have 52” of water to splash in. Here’s why:

Typically, you’ll build the base of your pool up to have a 2" pool bottom. Pair this with the usual 6" from the top of the pool wall to the actual start of your waterline (since pools are not filled all the way to the top of the walls) and the water depth will end up being a total of 8" shallower than the wall height; so 40", 44", and 46" of water respectively."...

https://blog.royalswimmingpools.com/how-deep-are-above-ground-pools

SE,

I expected your rather quick reply. Thanks. I looked at the Royal site, and have concluded that all their pools have to be classified as "permanently installed pools" according to the NEC because they are deeper than the 42" water depth and are intended to be left in place and filled with water for many years. That then brings up a related question:

NEC section 680.6(B)(1) notes that vinyl liners are nonconductive materials. However, how does one classify the metal wall that is outside the liner and restrains it--is it a "pool shell" (see 680.26(B)(2)? If so, it needs 4 uniformly spaced bonding points. I'd like your take on this. The TIA proposal I cited in the OP raises many possibly confusing and possibly wrong points.

Thanks--JMM

What a can of worms this is....I don't see any reason for all this bonding requirement, I can see it for the pump and light housing, but the rest just seems superfluous, I mean are they trying to guard against lightening strikes or what? It seems these requirements are also easily bypassed by coating the aluminum frame of the above ground pool, the depth of the pool also seems arbitrary, what if you only keep 42" of water in the pool, are they going to check?, I just don't see any reason for the depth of the pool to be an issue, you can empty any above ground pool and fold up the lining for storage....

I just don't see any rhyme or reason for all this grounding requirement...Above ground pools are not considered permanent installations and should be exempt from unenforceable regulations...this seems like bureaucratic harassment more than anything else...

..."Since 2002, CPSC is aware of 33 fatalities that involved electrocutions in swimming pools and spas. * There were 23 deaths from electrocutions in pools and spas from 2002-2014. ... No injuries or deaths due to electrocutions in pools and spas were identified in 2018."..

About 2 per year? I'm going out on a limb here and saying these regulations probably won't make any difference because more than that don't follow the codes anyway....Most of these are probably freak accidents from electrical extension cords overhead lines, appliances like the tv falling into the pool, and the very few lights left that are line voltage....

Ref...

The interpretation of the code rules can be very difficult to do. That is where having a listed product helps. I hope to hear from the company you mentioned soon, on the questions I asked them.

The equipotential bonding is important because it reduces the risk of shock from a fault's creating a voltage gradient from one area or point in the pool water to a person either in or contacting the water while effectively at a sufficiently different voltage. You have probably read a lot about "touch voltage", which is a real risk when energized lines are down and is also a real problem in the dairy industry's milk barns.

I would have appreciated further data from CPSC regarding the cause of each of those deaths and injuries. Much harder (or impossible) to find would be the data on injuries or deaths that were prevented because of the NEC requirements being followed. I suspect the low rates are, in large part, due to the reduced risks from following the rules--even though they can be very difficult to interpret.

--JMM

https://www.poolspanews.com/how-to/codes/preventing-shock-in-swimming-pools_o

One of times I went through formal NEC training on the codes was when the pool grounding requirement was added. The reason for any codes are never explained by the NEC but our group discussed possible reasons. We came up with what I believe are two plausible reasons:

1. An immersed individual in water presents a much larger current path surface area should any voltage potential gradient exists in the water. Defibrillation electrocution can occur at much lower currents and voltages than what one normally considers dangerous. Therefore any conductive materials in contact with the water a swimmer can touch should be bonded.
2. Bonding to the metals in contact with the water reduces a static charge build up to the pool surface to reduce the likely hood of a lightning strike directly to the pool. Bonding will not mitigate the damage from an actual strike. The idea is to prevent one from happening in the first place.

I don't know if these are the actual, critical reasons for bonding a pool. Remember electrical safety rules are not made from analysis of electric and biologic theory. They are made from failure analysis from rare tragic and near tragic incidents.

While the 42 inch water height does seem to be an arbitrary threshold for defining storable versus permanent pool designs a threshold should exist at some level.

I have seen in Europe and in the Caribbean Blow Up Tube pools that advertize a 4 foot depth and that they can hold up to seven adults.. these do not seem to have provisions for pumps or strainers and simply come with a ladder for getting in and out of. Also saw a portable hot tub of similar design advertised from a chinese site.

These are storable in that you let the water out, roll it up into a bag and store it in your shed. Since most UK and Caribbean back yards for normal people are around the size of an old cadillac, it makes sense that they would not use permanent pools.

Now, what could be happening in the USA is above ground companies are trying to put their pools in a different category from built in pools, so they can get an exemption from the rules. But I actually hope not. Because back in the late seventies I had a cousin almost die from being shocked in a pool.. she has not gone back in a pool since 1979..lol