By Mike Sokol
Welcome to my J.A.M. (Just Ask Mike) Session, a weekly column where I answer your basic electrical questions. If you’re a newbie who’s never plugged in a shore power cord (or ask – what’s a shore power cord?), or wonder why your daughter’s hair dryer keeps tripping the circuit breaker, this column is for you. Send your questions to Mike Sokol at mike (at) noshockzone.org with the subject line – JAM. This week we discuss the hazards of swimming near docks that have electric power.
Do I remember something you wrote about getting shocked around a boat dock? We’re getting ready for our first trip and will be staying by a lake with a lot of docks. What do I need to know to keep my family safe? —Stu
Yes, it’s that time of year again. Soon the kids will be out of school and many of you will be taking your first camping trip in more than a year. And yes, I have written a number of articles about something called Electric Shock Drowning, or ESD for short.
What is Electric Shock Drowning?
Well, Electric Shock Drowning can occur anytime you’re in water that’s been energized by an electric current. Basically, because water is a relatively poor conductor of electricity, if something like a metal conduit on a boat dock, or even an aluminum boat that’s connected to shore power, isn’t grounded properly, any electric fault current gradient will reach out dozens of feet in the water before grounding itself completely.
Why is this dangerous?
Well, let’s assume you’re swimming out in the water a hundred feet from shore and decide you want to swim to the dock. But as you get closer and closer, your arms and legs get really tired. So much so, that as you get a few dozen feet from the dock you may not be able to move them at all. Of course, if you can’t move your arms and legs while swimming, you’ll never make it to the dock. You may just sink and drown, a victim of ESD.
Is this being electrocuted?
Not really, since you may not sustain enough of a shock to put your heart into ventricular fibrillation, like can occur with an RV hot-skin voltage. And while there may be a few dozen deaths from ESD each year, there may be other unreported incidents due to the lack of sign of electrocution. That’s because you really weren’t electrocuted – you were paralyzed from electricity and the drowning did the rest.
What can I do to stay safe from Electric Shock Drowning?
Well, you should never swim around a dock that has any kind of electric power run to it. And note that there were some kids who died a few years ago while swimming between houseboats that were plugged into shore power on a lake. So that’s to be avoided as well. If a boat dock has any kind of lift, you can be sure it’s connected to electric power.
There can be other safety concerns. Just a few years ago a pair of fishermen died from electrocution in a parking lot where they had plugged their trolling motor into a battery charger that wasn’t grounded properly. They died in inches of water when they touched their aluminum boat that was energized to 120 volts by the extension cord plugged into the battery charger.
What if I feel a shock while swimming?
Reverse course and swim back the other way. DO NOT keep trying to swim towards the dock. If you do, the electric current will only get stronger until it overwhelms your nervous system and makes all your muscles lock up.
Most of the Electric Shock Drownings occur less than a dozen feet from the dock. No matter how strong of a swimmer you may be, you’re never strong enough to overcome the paralyzing effect of 120 volts AC in the water. Your arms act like antennas channeling the gradient current in the water directly into your body. There’s no way you can win this battle, so you have to retreat.
What if I see someone in a pool or near a dock who’s getting shocked?
DO NOT jump in and try to save them until the electric power can be shut off. And don’t try to throw them a life preserver and pull them to the dock. That’s happened a few times and the swimmer accidentally touched the metal conduit on the dock that was energized, which did electrocute them instantly. So make sure it’s powered down before any rescue is attempted.
CALL 911 FIRST, try to find out where to shut off the power, and attempt the rescue only after the electric power has been turned off.
What about docks with Electric Shock Drowning warning devices?
Some of my colleagues in the marine industry don’t trust them just yet, but I think it’s a good start. And docks are now being required by the NEC to use 30mA GFCIs on all power. But to be absolutely safe from ESD, you don’t want to swim anywhere near anything that’s plugged into electric power. As the old saying goes, water and electricity don’t mix. And that’s doubly true when you’re swimming in the water.
OK, everyone. Remember that electricity is a useful and powerful force, so we all need to pay attention to safety precautions while using it.
Let’s play (and swim) safe out there….
Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.
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