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Electrocution In The Bath

Posted on 2012-04-04
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You've seen it in various crime/thriller movies/episodes. Someone is sitting in the bath and a hair drier or radio falls or is pushed into the bath. After an exhibition of smoke/steam the bather dies!

Am I correct in assuming that this is rubbish and that the bather will feel nothing. The fuse and/or the elcb/rcd device will cut the supply.

Even if the supply is not cut, the current cannot flow through the bather .... it will go through the water to the metal of the plughole (which should be earthed). The bather will feel nothing.

Even if there is no metal plughole, the electricity cannot flow through the bather unless he/she touches a tap(faucet).

I haven't been quite confident enough in my beliefs to test this in the bath .... not yet anyway ....
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Question by:Eirman
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by:paulmacd
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GFCI circuits are relatively new (you must be young), but yes, that's exactly what they're supposed to do.

And no, you're not safe.  Electricity will take the shortest path, but that will change from moment to moment and sooner or later, you'll be in the way.
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by:rtay
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Prior to GFI it was possible.  The electricity would pass through the well conducting water  and the person until the power was cut off.  Probably causing death.  This is the reason that modern homes have GFI installed.  When overloaded the electricty is shut off.  Most bathroom appliances have a built in GFI also as a secondary precaution.  

As for today, it is unlikely you will die.  I probably won't be testing it out though.  

If you don't post back I will assume you tried it and it did not go so well.
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by:Dave Baldwin
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It is not complete rubbish and if you have your hands and heart in the direct electrical path, I wouldn't count on the GFI saving you.  Anytime you think you're 'safe', you're probably wrong.  Kind of like crossing the street with your eyes closed...
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by:Eirman
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I still cannot see how electricity can flow ..... through ..... the body.

On many occasions I have handled and twisted bare live 230 volt wires together whilst sitting on attic rafters. I couldn't feel a thing.
I was like a bird sitting on a 30kv wire .... there was no where for the electricity to flow.
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by:Dave Baldwin
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Then I wouldn't hire you, you're not safe to work with.
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by:d-glitch
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>>  On many occasions I have handled and twisted bare 230 volt wires while sitting in an attic.

But in the bathtub you are connected to through the water to the drain, which does connect to the earth ground.

Modern building codes require Ground Fault Interrupters in kitchens, bathrooms, and outdoors.
But older construction may not be protected.

The risk of electrocution associated with metal water supply and drain pipes is very real.
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by:d-glitch
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I remember reading about the invention of the GFI back in the 60's.

The responsible engineer put his daughter (wearing a bathing suit) in a bath tub full of water and dropped in a radio.
It worked fine.  But not a candidate for Father of the Year.
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by:Eirman
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> by: d-glitch
> But in the bathtub you are connected to through the water to the drain, which does connect to the earth ground.

I really don't understand. It's current that kills NOT voltage. Assume that the GFI & Fuse have failed .... the current will flow through the water to the plughole .... how can it flow THROUGH the bather. Consider the electric chair .... the head and ankles are at different potentials, therefore current will flow. In the bath your whole body is at the same potential unless you touch the tap/wall etc. Electric current takes the path of least resistance. Just sitting in the bath offers no potential difference .... therfore no path for current to flow.

I appreciate all the replies and I do not want to alienate my fellow experts.
I'm genuinely not trying to be smart or derogatory when I say this ..... You have all been fooled by hollywood!
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by:d-glitch
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Water is actually a poor conductor.  
If you are immersed in the water, you are the path of least resistance.

Under fault conditions, there is a potential gradient between the 120/230 VAC from the electrical system
and the 0 V at the drain.  If your body in immersed in this electric field, it will carry potentially lethal current.
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by:abbright
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Pure destilled water has a pretty high resistivity for electrical current (http://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity), while the human body has a much less resistivity due to all  the minerals, salts and ions it incorporates. Therefore as the current takes rather the way of less resistancy chances are pretty high that relevant amounts go through the body. Things might be different in salty water, though.
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by:paulmacd
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As electricity passes through the water, the water will heat until that path is no longer the easiest.  Repeat quickly.  Eventually, the body becomes the easiest path.  Maybe it kills you, maybe it doesn't, but I'm not going to try it.
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d-glitch earned 100 total points
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A number of bath tub electrocutions are reference here:  http://www.medline.ru/public/sudm/a2/art3-2-2.phtml
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by:rtay
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by:Eirman
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A bit of my own research over the past few minutes .....

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2743575/

http://www.allaboutcircuits.com/vol_1/chpt_3/4.html
http://www.allaboutcircuits.com/vol_1/chpt_3/3.html
Quote from the above "Electric shock can only occur when contact is made between two points of a circuit; when voltage is applied across a victim's body."

I also found several references to a mythbusters simulation ..... but they ONLY measured voltage .... bad science
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by:abbright
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Compare the situation in the bathtub with the situation in an "air tub". By "air tub" I mean the usual situation where the human body is immersed in air. While the resistivity of air is very low it is not absolutely zero (see flashlights).
So the current takes the way through the body even while it also could take the way through the air. The same holds for a body in the water. When it is "easier" for the current to take the way through the body than it is to go through the water it will do so. Then you have two points of a circut: The point where the current enters your body which is likely nearer to the radio and the second point which is likely your connection with the metal of the tub.
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by:Dave Baldwin
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You don't get current without voltage, they are inseparable.  And you don't seem to understand how little electricity it takes to affect the heart.  Dirty bath water is more than conductive enough to support a fatal level of current.  Since it can take as little as 3mA, with 120VAC source, a resistance of 40,000 ohms is low enough to be fatal.  While you may be able to drop your appliance in the water many times without incident, the only one that counts is the one that kills you.  Note that people with heart problems can be more sensitive.

Medical equipment is required to allow no more than 0.5 mA leakage current.  More info here: http://www.phihongusa.com/html/leakage_current.html

And you're ignoring the fact that under some circumstances, you can cause an explosion from electrical currents going where they shouldn't be.  If you have ever had an electrical outlet or stove burner short out, you would see white sparks shooting out.
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by:d-glitch
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>> I also found several references to a mythbusters simulation ..... but they ONLY measured voltage .... bad science

But if you actually watch the 4 minute MythBusters video link posted above, you will see that they actually measured
current and referred to it several times.
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by:aleghart
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We have a hot tub.  After a re-fill, sometimes the old breaker would trip during the initial heating of the cold water.  Happened with every re-fill.  So, last time, based on water temp of ~90F, that the heater tripped the circuit again. Dried off and shut off the tripped breaker and turned it back on.

After a few seconds, it tripped.  Without another thought, I reached up to reset it again.  Blip.  Instantly.  _Then_ I shut it all the way off, turned to my wife and told her to get out of the tub.

After moving it (while empty), I dropped it a bit harder than I had planned.  That force, combined with the age of the unit probably cracked some insulation in the heater wiring, which is causing a short...and tripping the breaker.  As designed.

Nobody died.  Didn't feel a thing.  We were both in the water.  We did not make a conducting path, either to ground or between wires or back to the panel.  But, I would not recreate the experiment without the GFI breaker.

While doing electrical work, I've held live 110 AC wire with current on them.  Nothing happened.  Even when somebody turned on wrong the breaker.  Until my hand brushed up against the metal box, and my skin became a pathway from live wire to ground.

At first, I thought I had cut myself on the mud ring.  I looked at my hand...no scratch.  Kept working, and it happened again.  No scratch.  Then my other hand started burning.  And I got a clue to stop leaning on the electrical box.

Touching something electrical will not kill you.  It all depends on where you are in the circuit.  Just ask the people who sit in a Faraday cage with lightning on the outside.
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by:d-glitch
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albright   >> While the resistivity of air is very low it is not absolutely zero (see flashlights).

The resistivity of air is very high.
A conservative engineering guide line is 10 kilovolts per inch.
What do you mean by flashlights ?
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by:abbright
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Sorry for my English: By flashlight I mean lightning (http://en.wikipedia.org/wiki/Lightning).
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by:Eirman
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> by: abbright
>Then you have two points of a circut: The point where the current enters your body which is likely nearer to the radio and the second point which is likely your connection with the metal of the tub.
I Agree .... in the above scenario there are two points of contact and a path through your body .... but if you are just sitting in the bath there is just one point and no electrocution. (I think you meant flashover)

> by: d-glitch
> But if you actually watch the 4 minute MythBusters video link posted above, you will see that they actually measured
> current and referred to it several times.
I'll have a look later. Thanks for the link

> by: DaveBaldwin
> And you're ignoring the fact that under some circumstances, you can cause an explosion from electrical currents going where they shouldn't be.
I agree, but for the purposes of this question, I am confining it to electricty.

I still remain convinced that current cannot flow through water ..... into your body ..... and out of your body into the same water at the same potential
It would defy physics.
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by:abbright
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Take for example the situation where the radio falls onto your lap in the water. The resulting resistivity of the current going the short way from the radio through the water to your body and from there to the metal can be a lot lower than the resistivity of the way from the radio directly to the metal as this is likely to be much longer.
In the first case you have a very short way of relatively high resistivity and a longer way of lower resistivity (the body) while in the second case you have a longer way of high resistivity which can lead the current to go through the body.
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by:aleghart
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>current cannot flow through water ..... into your body ..... and out of your body into the same water

This is why you can weld structural steel without killing people.  You clamp onto an I-beam many feet away.  Hit the joint with your welding tip or rod, and the current travels through the steel to the grounding clamp.

Anyone leaning or sitting on the steel structure will not be hurt.  And, you will not be damaging electrical circuits that may be grounded to structure.

I had a retrofit project that involved putting new sub-beams into an existing building, while occupied and while computers and everything else was turned on.  And crew were sitting, leaning, and hanging off the beam.
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by:abbright
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And of course you are right there will be differences in potential.
Going through the water the potential decrease all the way going to the metal but it will also decrease going through the body. As the water has a relatively high resistivity compared to the wire birds sit on this cannot be neglected.
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by:Eirman
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Think of it this way .... If you 60% fill a fully insulated plastic tub (no plumbing or anything else) with dirty soapy water, and put an unfused 500v bare live wire into the water, what will happen?
Nothing ... the electricity will have nowhere to go.

If you have bare feet and you put your hand into the water you will get a shock.

If you put on high spec insulated boots and put your hand into the water you will feel nothing (if you put your other hand on the wall you may feel something).

If you step into the bath in your insulated boots you will feel nothing  ... the electricity will have nowhere to go.

If you then take off the boots  you will feel nothing  ... the electricity will have nowhere to go.

If you carefully sit down without touching the wall  you will feel nothing  ... the electricity will have nowhere to go.

If someone else then puts a bare neutral/ground wire into the water at the other end of the bath I maintain that you will feel nothing because .....
If the live on its own caused no flow through your body why should it now flow THROUGH you when it has a perfect target .... the neutra/(ground wire
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by:d-glitch
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>>  I still remain convinced that current cannot flow through water ..... into your body ..... and out of your body into the same water at the same potential

But current can flow through water ..... into your body (at a high potential near the source) ..... and out of your body  into the same water (at a lower potential near the drain).
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by:abbright
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Once there is a way for the current to go it'll take the way of the least resistancy which might include your body.
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by:aleghart
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Why would current jump from water into your non-grounded body?
If the current is already passing through the water, it will continue to use that path to ground unless it finds a path to ground with less resistance.

So if you drop a grounding rod cable into the bath, the water will conduct current to the grounding rod, and not into the drain pipe, because the drain pipe will not be as good of a ground as the ground pipe sitting right next to the tub.

That's why you'd get electrocuted if standing in a tub of water that is 'hot' with electricity seeking a ground...and you reach out and touch a water spigot or metal light fixture.  You become the path to ground.
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by:aleghart
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If the nearness or contact with electrical current theory were true, then welders everywhere would be dead from welding with bare hands or leaning against a object while welding.

No shock unless the body comes _between_ the current and it's ground.
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by:abbright
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It's not the nearness or contact with electrical current that is dangerous but whether there's a difference of potential between one point of your body and another that makes the current flow through it.
So if there's only water and the radio in the tub the current will take the shortest way from the radio to the metal and the potential will decrease from 100% to 0 all the way. When your body comes in between this way you will find a difference of potential from the point nearer to the radio to the point nearer to the metal. This difference of potential might cause a current through your body which might kill you.
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by:aleghart
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Maybe I'm missing something in this scenario.  In modern plumbing, the nearest metal is the supply pipe.  Next would be iron drain pipe below the floor.

If you are touching the spigot, it could be threaded straight onto an iron pipe, which connects to the supply line with a metal fitting.  But nobody mentioned holding onto the spigot.  The handles are likely plastic, and unless you've removed the "Hot" and "Cold" caps to expose the screws, there is no contact with metal.

Bathtub drains are PVC with a rubber gasket or plumber's putty.  Connecting to older iron pipe waste system would be with a flex rubber joint.  So, water would conduct to the iron pipe while draining.  A lot of residential drain is ABS plastic...so the chances of striking a ground are pretty low.

How does one fit his body into the drain to come between the water & an iron drain pipe?

I think the grey area here is where theory meets the real world.
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by:Dave Baldwin
Dave Baldwin earned 50 total points
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Electricity will not flow thru Pure Water with no contaminants.  Lead acid batteries used to start your car contain water contaminated with sulphuric acid.  Electricity flows very well there.  In between those two extremes are many circumstances where electricity will flow to varying degrees thru water.  In particular, extremes of high or low pH will support the flow of electricity.  http://en.wikipedia.org/wiki/PH  Info from the EPA also: http://water.epa.gov/type/rsl/monitoring/vms59.cfm  You can find a few million pages on the conductivity of water because it is one of the indicators of water quality.

The problem with your statements above about the wire in the bath water is that things Often go wrong.  And when they do go wrong because someone slipped and touched something they shouldn't, they can be hurt.  Safety is not about 'normal' circumstances but about preventing the dangerous ones.
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by:PCableGuy
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I think if you're in a tub of water, your electrical resistance is most likely lowered. If the electricity gets under your skin and inside you, the resistance is probably even lower in the body. Nerves conduct electricity easily, and who knows what else inside you conducts easily.

Regarding the drain being the ground/pathway. Don't forget that the power plug going into the radio's power supply has a hot and ground provided via the electrical outlet. Once the radio hits the water, I don't think the current is passing thru the radio's power supply anymore, it's going to jump from hot->to path of least resistance->to ground, possibly thru the electrical outlet.

Plus, once you're water logged, you have created many pathways for electricity. Skin absorbs water.
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by:Eirman
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I had a look at the mythbusters video and you are correct .... current was measured.
However, it was not made clear how the dummy was connected up.

In the first diagram, the foot appears to go below the line of the bath. Also at 55% into the video there is a glimpse of a diagram with a ground wire heading up (to where?).
Conclusion .... this does cause some doubt in my open mind ..... I need to know more about the wiring before a concrete conclusion.

Another thought .... What to you think the entry and exit points are for the electric current. In through the toes and out through the navel (or some other unmentionable part(s))
In the electric chair, the current enters through the head and exits through a leg. One point would not work!  http://answers.wikia.com/wiki/How_does_the_electric_chair_work
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by:d-glitch
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My seven relevant comments (not including this one) seem to have slipped by unrewarded.
An observation, not an objection.
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by:Eirman
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I'm sorry d-glitch, I thought I had given everyone who had intelligently participated some points (and you certainly had!). I never had this many replies to a question before and I was chopping and changing points, giving point twice to the one person, then removing them then looking at my 500 target so often that I missed or deleted your points.

Sorry again d-glitch, I'm sure I'll catch you again. Here's five consolation stars *****

As I type I see that the question has not been closed as it should have been
I brought this question up in EE Bugs as is should have closed automatically, but it has not closed. I'll try closing again in a fairer manner.
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by:Eirman
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I'm really none the wiser after all this. However, enough doubts have been raised in my mind not to carry out a practical experiment.

Many thanks to everyone for your contributions. They were much appreciated .... even if you didn't get any points.

In haste, I had awarded zero points to myself, giving me a second opportunity to close.
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