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Author Topic: Swimming Pool Electrocution  (Read 6722 times)

Mike Sokol

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Swimming Pool Electrocution
« on: March 31, 2016, 03:58:34 pm »

Anther forum member brought this to my attention (Thanks, Tim), and it's a very sad story about a SF business executive being electrocuted in his swimming pool while trying to save his children from shock-drowning. http://www.sfgate.com/bayarea/article/Silicon-Valley-exec-dies-trying-to-save-daughter-7216737.php

Since we're now entering pool season, and many of us may be doing sound gigs around swimming pools and open water, you need to extra vigilant about proper equipment grounding.

I've contacted the reporter who wrote this story to get more intel, but it's been suggested that a wiring problem with the pool lights electrified the water.  I've been trying to get some traction with OSHA to offer CPR and Electrical Awareness Training to pro-sound crews, so if any of you are certified CPR instructors or EMT's, please contact me directly to discuss.
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Jonathan Johnson

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Re: Swimming Pool Electrocution
« Reply #1 on: March 31, 2016, 05:49:21 pm »

Seems to me having an EPO (Emergency Power Off) switch for swimming pool electrics (lights, pumps, and heaters) would be a good idea. In addition to electric shock, I've heard of people being trapped against pump intakes. (The lights and heaters, at least, should be GFI protected anyway.)

Of course, that assumes that people will have the presence of mind to shut off the power in an emergency situation. Perhaps the EPO circuit could be linked to emergency equipment stowage: if someone grabs a life ring, for example, all power is cut off (and an alarm is sounded). In facilities equipped with monitored alarms, EPO could alert emergency responders automatically.

The thing is, most people who might respond to a swimmer in distress won't know whether electricity is involved or not. In an emergency, you can't presume to know the cause before intervening, so signage and training should be to shut off power in ANY swimmer-in-distress emergency.

I know this is out of the realm of "audio", but I figured I might as well share the thought. It's certainly not a well-developed idea, there are many things to consider. Maybe someone reading this will be able to protect other people using these ideas as a basis.

Well, bringing this back to "audio", baptismal pools with electrics should also have an EPO. In addition to an EPO switch near the pool, put one in the control booth -- and train people to recognize a person in distress. That may not be the Spirit moving them...
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John Roberts {JR}

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Re: Swimming Pool Electrocution
« Reply #2 on: March 31, 2016, 05:53:44 pm »

Maybe teach the pool puppy (the automatic cleaner every pool uses) to bark if it senses any voltage gradient.

Seems this should all be preventable.

JR
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Corey Scogin

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Re: Swimming Pool Electrocution
« Reply #3 on: March 31, 2016, 06:03:10 pm »

I'd be interested in the specifics.
How was current flowing in such a way to electrocute a swimmer?
Was the person in contact with an electrified piece of metal? Or a grounded one?
Is the resistance of pool water higher than the resistance of a human body such that merely being in the water may cause current to flow through a person?
Do any of these questions even matter because there are too many variables to consider, they'll differ in every situation, and the entire system should be GFCI protected?
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Mike Sokol

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Re: Swimming Pool Electrocution
« Reply #4 on: March 31, 2016, 06:08:01 pm »

Of course, that assumes that people will have the presence of mind to shut off the power in an emergency situation.

I'll do more digging, but my point of posting this thread is to make all of you aware of the extra dangers of electric shock around water. Typically a swimmer begins to lose control of their muscles the closer they get to the source of the leakage current. And when you can't move your muscles, you just slip below the surface and drown. It's really important to turn off the source of the current BEFORE getting in the water to help someone in distress. And, of course, hindsight is 20-20 and I'm sure that most times nobody is aware there's a shock that's causing the swimmers to be in distress. So education is the key to saving lives. That and a big cutoff switch with a GFCI are probably the best ways to save lives.
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Mike Sokol
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Mike Sokol

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Re: Swimming Pool Electrocution
« Reply #5 on: March 31, 2016, 06:11:07 pm »

I'd be interested in the specifics.
How was current flowing in such a way to electrocute a swimmer?
Was the person in contact with an electrified piece of metal? Or a grounded one?
Is the resistance of pool water higher than the resistance of a human body such that merely being in the water may cause current to flow through a person?
Do any of these questions even matter because there are too many variables to consider, they'll differ in every situation, and the entire system should be GFCI protected?

It's called ESD for Electric Shock Drowning, and the freshwater boating industry has been working on this for a few years. In fact, I've consulted with some of their presenters about how it works. See here for specifics, and I can answer questions on it as well. http://www.boatus.com/seaworthy/ESD.asp

And here's a really good basic description from my buddy Dave Rifkin: http://www.qualitymarineservices.net/
« Last Edit: March 31, 2016, 06:13:18 pm by Mike Sokol »
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Jonathan Johnson

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Re: Swimming Pool Electrocution
« Reply #6 on: March 31, 2016, 06:13:12 pm »

That and a big cutoff switch with a GFCI are probably the best ways to save lives.

A GFCI is a must... but I wouldn't trust it to be the sole means for interrupting voltage. A Big Red Button would be a worthwhile addition.

Do commercially-produced audio distros provide for an EPO circuit? I know that some UPSs do.
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Tim McCulloch

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Re: Swimming Pool Electrocution
« Reply #7 on: March 31, 2016, 06:58:35 pm »

A GFCI is a must... but I wouldn't trust it to be the sole means for interrupting voltage. A Big Red Button would be a worthwhile addition.

Do commercially-produced audio distros provide for an EPO circuit? I know that some UPSs do.

It's the big circuit breaker on the front.  They can be ordered with shunt trip terminals for remote kill.
« Last Edit: April 01, 2016, 12:20:03 am by Tim McCulloch »
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Stephen Swaffer

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Re: Swimming Pool Electrocution
« Reply #8 on: March 31, 2016, 10:29:53 pm »

One of the changes to the NEC in 2014 was a requirement to bond the pool water.  No doubt to make sure there is a good path to trip GFCIs.  It appears to me that nearly everything anywhere near a pool must be GFCI protected or low voltage.

The problem is, virtually no one requires older installs to be brought up to date-so pool that is even 5 or 6 years old could have issues addressed by 2 cycles of code updates.

Maintenance is another issue-how many of the GFCI's are tested every 30 days as required?  At a bare minimum-make sure yours get tested before the season starts!
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Frank Koenig

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Re: Swimming Pool Electrocution
« Reply #9 on: March 31, 2016, 11:21:28 pm »

This one hit pretty close to home. I didn't know the victim personally but he and his family are good friends of a close friend of mine. His kids and my friend's grand kids hung out together a lot and, needless to say, the grand kids, while not present at the event, are devastated. To be clear, this occurred in the city of Palm Springs, California, not at the victim's residence in Burlingame. I think it was at an Air B&B or the like.

I am very interested in learning the results of any investigation both for my own edification and, as I'm considered the "electrical guy" in my group, to answer others' questions.  So, Mike, I really appreciate anything you can dig up through your channels. I'm not holding my breath for the media. And no, I'm not getting involved the the inevitable lawsuits.

As to the bonding of pools, it is interesting that "bonding the water" is a recent addition to the code. When my folks had a pool built back in 1968, I clearly recall that there were ground clamps on the rebar cage of the pool with  copper wires running to clamps on all the copper pipes, as they used at that time. The whole shebang got embedded in the gunite. I guess now with PVC pipe being the norm it take a bit more explicit wiring to achieve a good bond.

I've seen E-stop mushroom switches on some public pools. I don't know if and where they are required, but they sound like a really good idea.

--Frank

 
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Steve M Smith

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Re: Swimming Pool Electrocution
« Reply #10 on: April 01, 2016, 02:43:51 am »

I'm struggling to understand the cause of this.  Is it leakage from the water pump?  I can't think of any thing else electrically operated which would come into contact with pool water.


Steve.
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Mike Sokol

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Re: Swimming Pool Electrocution
« Reply #11 on: April 01, 2016, 07:03:16 am »

I'm struggling to understand the cause of this.  Is it leakage from the water pump?  I can't think of any thing else electrically operated whi bch would come into contact with pool water.

Over here in the states we like electric lights inside our pools, underneath the water. And while modern code calls for them to be low voltage, there's got to be many thousands of pools in the US with 120-volt AC lighting. And these were likely installed before GFCI technology matured and has been mandated. So the only thing protecting humans from being shocked is the gasket around the lens keeping the water out of the bulb socket.

The real insidious thing about freshwater shocks is that unsalted water itself is a fairly poor conductor. So instead of "grounded" water shorting out the circuit and tripping the over-current protection device, this 1 to 2 ampere current spreads out though the water in a gradient which reaches many feet, sometimes up to 50 or 60 feet depending on the salinity of the water. So imagine an infinite number of resistors in series/parallel, with 120 volts on the light bulb socket, then gradually reducing down to 0 volts maybe 20 feet away. If you had 10 ft long arms and reached one hand near the electrified bulb housing at 120 volts and the other hand near the "grounded" water at zero volts, you would obviously be receiving a 120-volt hand-to-hand shock. A wet human body is around 1,000 ohms hand-to-hand, so you would receive a 120-ma shock, which is certainly deadly. But since we don't have a 20 ft reach, what happens if we're in the same gradient electric field with our arms doing a more normal 5 ft span? In that case your arms act like a dipole antenna with one hand maybe at 60 volts and the other hand at 30 volts. Now you have 30 volts difference from hand-to-hand which creates a 30 mA current flowing through your body. Since the human body is paralyzed with anything much over 20 mA of 60 Hz current, this is what causes swimmers in a freshwater voltage gradient to drown. Simply put, they really don't get "electrocuted" in a pool with leaky underwater lights or while swimming towards a dock with a energized conduit hanging in the water. What happens is the closer a swimmer gets to the current source, the more their arms become paralyzed, and because they can't swim, they just sink and drown. Since there's generally no signs of electrocution in this situation (and they really weren't electrocuted in the first place), I believe there's a lot more Electric Shock Drownings than reported. Most of these ESD deaths are probably attributed to swimmers getting tired and drowning.
   
« Last Edit: April 01, 2016, 08:29:24 am by Mike Sokol »
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Mike Sokol
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John Roberts {JR}

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Re: Swimming Pool Electrocution
« Reply #12 on: April 01, 2016, 09:29:20 am »

@mike, have you looked at the impact of pool chlorine on water conductivity?

How open are people about sharing accident details if there may be liability lawsuits?

JR
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Mike Sokol

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Re: Swimming Pool Electrocution
« Reply #13 on: April 01, 2016, 09:39:44 am »

@mike, have you looked at the impact of pool chlorine on water conductivity?

How open are people about sharing accident details if there may be liability lawsuits?

JR

Not looked at chlorine, but it has to increase the conductivity of the water. Most of my intel on electrocution deaths has come from the local police who did the investigation. I identify myself as a writer and blogger about electrical safety, and they'll generally share any details that can be made public. 
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Mike Sokol
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Stephen Swaffer

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Re: Swimming Pool Electrocution
« Reply #14 on: April 01, 2016, 01:33:49 pm »


As to the bonding of pools, it is interesting that "bonding the water" is a recent addition to the code. When my folks had a pool built back in 1968, I clearly recall that there were ground clamps on the rebar cage of the pool with  copper wires running to clamps on all the copper pipes, as they used at that time. The whole shebang got embedded in the gunite. I guess now with PVC pipe being the norm it take a bit more explicit wiring to achieve a good bond.

I've seen E-stop mushroom switches on some public pools. I don't know if and where they are required, but they sound like a really good idea.

--Frank

Bonding the rebar and creating an "equipotential" plane/grid has been around for some time.  The requirement to actually bond to the water itself is new.  Perhaps construction techniques using plastics is driving this as well-I really don't know.  The instructor explained that if you had a metal ladder going into the pool with 9 sq inches in direct contact you were covered.

Lawsuits are unfortunate (I certainly sympathize with those who have lost loved ones) in that they cannot undo the damage and no amount of money can replace the loss.  As an incentive for people to do things right they have some value-but fear of lawsuits is a hindrance to open communication.  I wish more people realized that many requirements of the NEC (though admittedly political at times no doubt) are driven by statistics and knowledge of injuries and deaths that most of us are not privy to.  So while something may seem silly or unnecessary (those pesky noisy ground pins), in many, many cases there are people out there that would gladly give any amount of money to role back the clock and install that safety requirement so they could still have their loved ones around.
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Mike Sokol

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Re: Swimming Pool Electrocution
« Reply #15 on: April 01, 2016, 01:57:31 pm »

As to the bonding of pools, it is interesting that "bonding the water" is a recent addition to the code.

There are several water-shock modes that I'm aware of. This is not an all-inclusive list... just what I've thought about so far.

1) Water electically grounded, touching something electrically hot. This is the classic "standing in the pool with your electric guitar in your hands" fail. Note that the fault current flows from your hand, through your chest/heart, and out through your legs in water. Similar to getting shocked while standing with bare feet on damp concrete, but even more deadly due to everything being very wet.

2) Water electrically hot, touching something electrically grounded. This is what happened to the preacher in Waco Texas while standing in a baptismal pool and someone handed him a properly "grounded" microphone. Fault Current travels from your legs up through your chest and out your hand. Again, very deadly. A little girl in Florida died a few years ago while retrieving a golf ball from a miniature golf course pond. In both cases, there was a break in the hermetic seal of the water pump or heaters, allowing the "ungrounded" water to be electrified to line voltage.

3) Water grounded, an electrified conductor stuck in the water. This is what causes ESD (Electric Shock Drowning) in situations like the recent pool death. As I described earlier, in freshwater there's a voltage gradient that can reach out dozens of feet from anything electrified that's stuck in the water. Could be an aluminum boat, or an underwater light fixture, or a dock conduit hanging in the water. These are really dangerous since you don't have to touch or be anywhere near the source of the current. If you get between the current source and the ground path gradient, then you become a dipole antenna picking up maybe 10, 20, 30 or more volts, hand to hand. Remember, a wet human being is around 1,000 ohms resistance, so even 10 volts hand-to-hand is a healthy shock, 20 volts can paralyze you so you can't swim and may drown, and 30 volts can cause actual electrocution under perfect conditions. 

In all of these ESD incidents you'll notice that the media reports CPR being started immediately. However, if the EMT's are delayed due to traffic, CPR will only keep you alive for a limited time. Far better to have a AED (Automated External Defibrillator) at every pool, and not be afraid to use it. Again, that's something I want to develop as a training course for pro-sound crews.
« Last Edit: April 01, 2016, 01:59:37 pm by Mike Sokol »
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Mike Sokol
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Thomas Harkin

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Re: Swimming Pool Electrocution
« Reply #16 on: April 01, 2016, 02:47:52 pm »

Not looked at chlorine, but it has to increase the conductivity of the water. Most of my intel on electrocution deaths has come from the local police who did the investigation. I identify myself as a writer and blogger about electrical safety, and they'll generally share any details that can be made public.

And gaining in popularity around here are saltwater pools, instead of chlorine.
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Mike Sokol

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Re: Swimming Pool Electrocution
« Reply #17 on: April 01, 2016, 02:58:12 pm »

And gaining in popularity around here are saltwater pools, instead of chlorine.

Saltwater is pretty safe from ESD since it shorts out most anything immersed in it. For instance, my boating guy who does ESD experiments in ocean water needs a 30-amp variac to electrify an aluminum boat. In fresh water, the same boat might draw a few amperes at most. But saltwater very dangerous if you're standing in it with an electric guitar plugged into a power outlet.
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Mike Sokol
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ProSoundWeb Community

Re: Swimming Pool Electrocution
« Reply #17 on: April 01, 2016, 02:58:12 pm »


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