Stray current dangers

This was posted on another site a few days ago and I don't believe I've seen it here before. It gave me the best explaination of stray current problems, how to check for and fix them, and the real dangers associated with them. It is over an hour but every minute is informative. I'll be checking my boat this weekend.

Hot Docks, Hot Boats and Electric Shock Drowning - YouTube

I think we've had two or three kids up in Tennessee or north Georgia who were electrocuted while swimming in or around the docks at the marina. Sometimes it's the marina's fault, but most often it's the boat owners fault.

Very informative. Thank you for sharing

Rambler said:

I think we've had two or three kids up in Tennessee or north Georgia who were electrocuted while swimming in or around the docks at the marina. Sometimes it's the marina's fault, but most often it's the boat owners fault.

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It couldn't be the kid's fault? Or their parent's fault?

Swimming in a marina is pretty much like playing in the street. A pretty foolish thing to do.

rwidman said:

It couldn't be the kid's fault?

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Only if they pulled the power cords into the water.

Here is one of the stories:
3 children electrocuted while swimming in lakes; 3 drown in river - U.S. News

And it seems the one was apparently the fault of faulty wiring at the marina. Hardly the kids fault.
Tennessee marina where electrocution occurred files corrective plan

But in general, lacking the shock hazzard, swimming at the marina is not the safest thing to be doing. Still, kids don't know that. Parents should. Boaters even more so.

Very Sobering, every boater should see this.

Thanks my marina is full of old boats and house boats. I going to do a little checking other boats around my boat to make sure it's safe to be in the water. last year I rewired a Albin trawler that had been wired to the shore power with reverse polarity. It stared out with a simple job of installing a few ground fault interrupter outlets and just grew and grew as one thing after another reared it's ugly head. What I didn't think about was how little amperage it takes to kill. This boat had it been in fresh water would have been deadly. My current dock neighbor built his own 50' house boat and had a house electrician wire it. I'm going to check him out. Our delta water isn't pristine but it's fresh. Kids swim around the docks all the time. In spite of written warnings so have I. I don't think I'll be doing that anymore.

Rambler said:

Only if they pulled the power cords into the water. .

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An undamaged power cord pulled into the water while still attached to the boat is not a haazzard. It's insulated.

A power cord not plugged into the boat, but pulled into the water should not be a hazzard because anyone who can follow written instructions will have turned the breaker off at the pedestal before unplugging the cord from the boat. Failing that, dropping the energized cord into the water should trip the breaker on the pedestal.

The hazzard I see to swimming in a marina is the danger of being hit by a moving boat. Just like playing in the street except that boats don't have brakes.

Swimming in a marina is pretty much like playing in the street. A pretty foolish thing to do.[/QUOTE]


Pretty much say's it all.

SD

rwidman said:

The hazzard I see to swimming in a marina is the danger of being hit by a moving boat. Just like playing in the street except that boats don't have brakes.

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Must be a regional thing. I understand SD up in Alaska but the Carolina/Gulf Coastal areas and inland waterways? I see it quite often in my sliver of America.

FWIW If swimming in the marina is like "playing in the street" you must have some awful busy marinas in your area. The larger ones perhaps? Many of ours are smaller, 50 slips or less and fairly quiet to boot.

People swimming off private docks at their house is extremely common too.

Rather than painting all swimmers as irresponsible idiots incapable of using common sense, would it be more prudent to know the danger may exist and inspect for problems before you accidentally fall off the dock and get electrocuted? It never was exactly at the top of my list of possible dangers from slipping and falling in the water before I watched this video.

In the video it mentioned testing for current using a voltmeter, I didn't catch just how that is done anybody have a source for detailed instructions and aditional items needed for the meter and cables. I understand there is a similar test method to check for galvanic corrosion any reccomendations there?
Thanks,
steve W

Steve said:

In the video it mentioned testing for current using a voltmeter, I didn't catch just how that is done anybody have a source for detailed instructions and aditional items needed for the meter and cables. I understand there is a similar test method to check for galvanic corrosion any reccomendations there?
Thanks,
steve W

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I'd have to watch it again when I get to my computer but believe he gave a couple of email addresses for contact and additional information.

CPseudonym said:

Must be a regional thing. I understand SD up in Alaska but the Carolina/Gulf Coastal areas and inland waterways? I see it quite often in my sliver of America.

FWIW If swimming in the marina is like "playing in the street" you must have some awful busy marinas in your area. The larger ones perhaps? Many of ours are smaller, 50 slips or less and fairly quiet to boot.

People swimming off private docks at their house is extremely common too.

Rather than painting all swimmers as irresponsible idiots incapable of using common sense, would it be more prudent to know the danger may exist and inspect for problems before you accidentally fall off the dock and get electrocuted? It never was exactly at the top of my list of possible dangers from slipping and falling in the water before I watched this video.

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Here in Jersey they swim in all the lagoons too which are way busier than the local marinas...they also swim in and across the intracoastal waterway. Heck they even jump off the bridges into the channels.

I'm not saying any of it's smart recreation...but many people do it so others think it's acceptble.

Then you have the people who tube, ski, kneeboard the busy ntracoastal and even have people in tubes when the pull up to the very busy fuel docks.

Around here....it's vacation mentality..."I'm on vacation having fun...therefore everyone else has to give me room to be happy"

I am on the great loop in Canada and so many swim in marinas it's crazy. I caution about electrocution, I learned about this manyyears ago, but people just shrug their shoulders and really don't care about the potential danger.

I wonder what professional divers (hull cleaning, zincs, etc) do before entering the water to check for electrocution? Many non-pros do the same thing all over, all the time.

It's not really swimming so I'm not sure it violates the "no swimming signs" that many marinas post.

At my marina the current is at least 10X the danger for swimmers than boats..unless you go in at slack curent.

I would LOVE to know how to check for voltage in the water- seems it would be a very practical thing to know how to safely and correctly do. It also amazes me how many times we see people swimming in marinas- besides all the cables running under water and support bars for our typical floating docks, there is always the electricity concern and how parents don't think of this before letting their kids swim is beyond me. If my kids want to swim at the dock we either go to the marina pool or kayak or dinghy out of the marina and jump in if we are not taking out the big boat!

Woodsong said:

I would LOVE to know how to check for voltage in the water- seems it would be a very practical thing to know how to safely and correctly do. It also amazes me how many times we see people swimming in marinas- besides all the cables running under water and support bars for our typical floating docks, there is always the electricity concern and how parents don't think of this before letting their kids swim is beyond me. If my kids want to swim at the dock we either go to the marina pool or kayak or dinghy out of the marina and jump in if we are not taking out the big boat!

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I wonder if it's like getting hit by lightning...a one in a XXX chance.

When my marina got rewired a few years back...the electrician said to me "holy shi*, you could plug a toaster in my assistance vessel slip. I and several divers had been under the boat several times in the preceding few years with no sensation anything was wrong.

So I don't know... but I guess I'll ask the pro divers I know and do some research...if I or anyone finds the answer that IS PRACTICAL FOR MOST OF US...it probably would be greatly appreciated if it gets posted!

When I say that swimming in a marina is "stupid", I'm not talking about divers who clean boats in a slip and I'm not talking about people swiming around private docks, I'm talking about swimming back and forth across the fairway with boats coming and going. The risk is being hit by a moving boat or causing a boat operator to wreck while trying to avoid the swimmer.

I understand how a ten year old child might not be able to think this out, but his parents should be able to. So should older children.

We have this situation in my marina from time to time when dry stack boaters take a slip for the weekend.

psneeld said:

I wonder if it's like getting hit by lightning...a one in a XXX chance.

When my marina got rewired a few years back...the electrician said to me "holy shi*, you could plug a toaster in my assistance vessel slip. I and several divers had been under the boat several times in the preceding few years with no sensation anything was wrong.

So I don't know... but I guess I'll ask the pro divers I know and do some research...if I or anyone finds the answer that IS PRACTICAL FOR MOST OF US...it probably would be greatly appreciated if it gets posted!

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From everything I have ever read the risk of shock is much greater in freshwater environments than salt water. I see divers hop in at the docks up here on the river all the time without testing anything first and I always think- dang- I hope all the electrical is ok!

rwidman said:

When I say that swimming in a marina is "stupid", I'm not talking about divers who clean boats in a slip and I'm not talking about people swiming around private docks, I'm talking about swimming back and forth across the fairway with boats coming and going. The risk is being hit by a moving boat or causing a boat operator to wreck while trying to avoid the swimmer.

I understand how a ten year old child might not be able to think this out, but his parents should be able to. So should older children.

We have this situation in my marina from time to time when dry stack boaters take a slip for the weekend.

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Ok..whatever..it's done all around the globe...stupid or not...better be carefull of people in the water....

psneeld said:

I wonder what professional divers (hull cleaning, zincs, etc) do before entering the water to check for electrocution?

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A prudent hull cleaner will unplug the boat he is working on from the shorepower, however, many (probably most) do not and never suffer any problems.

That being said, almost all electric shock drownings occur in freshwater. It is almost unheard of in saltwater. To say that swimming in a (saltwater) marina is foolish or even particularly dangerous is simply ignorant. For example, in the 18 years that I have been cleaning boat bottoms here in the Bay Area, well over 1,000,000 in-water service events have taken place, virtually of them in marinas, without a single electric shock drowning occurring.

I don't think divers unplug the boat. There could be too many issues with loss of refrigeration, battery charging, air conditioing, etc. when current is restored. Specifically, breakers on the boat tripping because of the surge of everything coming back on at once.

{quote]To say that swimming in a (saltwater) marina is foolish or even particularly dangerous is simply ignorant.[/quote]

You haven't been paying attention. That's ignorant.

rwidman said:

I don't think divers unplug the boat.

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Of course they do. I'm a hull cleaner, have been for 18 years and have unplugged almost every one of the 20,000+ boats I have ever cleaned. Any diver using an electric hookah is likely to unplug the boat he's working on, if not for safety reasons then at the very least so he can plug his air compressor in.

rwidman said:

There could be too many issues with loss of refrigeration, battery charging, air conditioing, etc. when current is restored. Specifically, breakers on the boat tripping because of the surge of everything coming back on at once.

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I'm not going to speak for anybody else, but if it's a choice between my safety in the water or your air conditioning, I'm choosing my safety. I don't have any clients who have a problem with that. And if they do, they're free to find another diver.

We're probably not talking days on end to clean the hull. The food in the fridge is going to be ok. And you can sweat while your hull is cleaned, or go do something on shore. And if your batteries are that weak that they can't go a little while without a charge, then you have more problems than a dirty hull.

Rambler said:

We're probably not talking days on end to clean the hull. The food in the fridge is going to be ok. And you can sweat while your hull is cleaned, or go do something on shore. And if your batteries are that weak that they can't go a little while without a charge, then you have more problems than a dirty hull.

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+1

A large power boat could typically be cleaned in 1-1.5 hours, at the most.

Shocking news...

As one who has been shocked in the water while removing a crab trap line from a prop shaft on a commercial ferry... it does happen. If you do work on your boat keep in mind that simply turning of the breakers at the dock end does nothing to lessen the shock hazard from OTHER boats to the ground path through YOUR boat. Disconnect the cord, remove the path to ground.

Our hull cleaners have always disconnected the shore power cord prior to getting in the water
HOLLYWOOD

hollywood8118 said:

As one who has been shocked in the water while removing a crab trap line from a prop shaft on a commercial ferry... it does happen.

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Yes, but getting shocked and electric shock drowning are not the same thing. I know a diver who tells the story of how, as he swam towards a boat he was about to clean, his eyeballs started vibrating. He got out of the water in a hurry on that one!

hollywood8118 said:

If you do work on your boat keep in mind that simply turning of the breakers at the dock end does nothing to lessen the shock hazard from OTHER boats

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Unfortunately, you can't unplug all the boats. So you pays your money and you takes your chances. But again, I've been in this business a long time and to my knowledge, no hull cleaner around here has ever been killed or seriously injured due to electric shock while in the water. But it only has to happen once to ruin your day. That's why we unplug 'em.

This is what I do and understand as I have had several marine electrician check/do work on the Eagle. It does not mean its 100% correct, so don’t go postal.


You can check for stray electricity through the AC ground, green wire and the neutral wire with a volt meter at a plug in. I would leave the power cord plugged in as the AC ground wire is usually the best to ground. You can also measure the water by dropping one end in the water and connecting to the metal support of the dock power, which should be grounded. However it’s not the volts that kill you it’s the amps. Most marinas/boats have stray electricity at a low level, and in marinas that have maintenance crew they can tell you the level and/or they can do some checking for you. Every time a new boat moors close to us, I check for stray electricity, and if concerned have the marina check also. The down side, if it our boat they will turn off the AC power until fixed. IF higher than normal/acceptable level best to hire a marine electrician.


Most high amp demand items like battery chargers, heater, water heaters, stoves/oven produce some stray electricity, so when testing with them on and off. Our battery charger is the highest producer. Make sure all the high amp items are connected to the AC ground. The biggest cause is AC wired back words as most people think the black wire is HOT like DC. The easiest way to check is a AC electrical plug tester sold at hard ward stores. When away from the dock the zinc loop becomes the ground path to earth, so it’s a bigger chance of being electrocuted in fresh water as fresh does not conduct electricity, and salt does.

So you can do some simple testing. Like I said don't go POSTAL if you don't agree.

fstbttms said:

Of course they do. I'm a hull cleaner, have been for 18 years and have unplugged almost every one of the 20,000+ boats I have ever cleaned. Any diver using an electric hookah is likely to unplug the boat he's working on, if not for safety reasons then at the very least so he can plug his air compressor in.


I'm not going to speak for anybody else, but if it's a choice between my safety in the water or your air conditioning, I'm choosing my safety. I don't have any clients who have a problem with that. And if they do, they're free to find another diver.

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I have never seen it done at my marina. If my diver unplugged the boat and the main breaker tripped and the batteries ran down because the refrigerator was on DC power without a charger and the food spoiled, I would be finding a new diver. I suspect my friends would do the same.

There's no shortage of people willing to dive boats for a living in my area.

edit: re: "you can't unplug all the boats", of course you can't. If you try, you are apt to find someone who seriously objects to you unplugging their boat. At best, he will plug it back in and say nothing. At worst, you might find yourself in a physical confrontation over the issue.

And for the poster who commented that the food wouldn't spoil in the time it takes to clean a boat, read my post before you respond to it.

Can't speak for other marinas or dive services but the one in our marina doesn't unplug ground power cables before diving. I know this because we've been on the boat a few times when our twice-yearly scheduled dives occured. I have no idea if they perform any sort of inspection of the ground power cables on the boat they're diving on and the surrounding boats before they go into the water.

I don't do enough corrosion work to get too much in detail on this subject but one quick easy test to do without disturbing anything can be done to your shore cord using a clamp on multi-test meter. Clamp your whole shore cord using AC amps scale and note your reading. Turn off the pedestal breaker and note your reading again then subtract the pedestal off figure from the other. <100 ma freshwater and <500 ma saltwater is OK. This lets you know if you have AC current leakage. A clamp on meter would typically read zero when you clamp a whole cord but if some of the current is leaking it will pick up the difference.