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Posted by mike_kaiser (My Page) on
Sat, Apr 20, 13 at 7:56

The mother-in-law's basement flooded the other day. By the time I arrive there's 5+ feet of water down there. Get pumps going and after many hours the waters are receding and I can see a stream of water gushing up in the the location of the sump pump. Turns out one of the rubber fittings that hold the back flow valve had let no water was exiting the house.

Here's where things get really weird. The receptacle where the sump pump was plugged in had been under water for 8+ hours, yet the pump is still running. Maybe not the brightest idea but I walk up and pull the plug. The battery back-up kicks in! The battery is sitting in one of those plastic trays on the floor and is filled with water. So I pull the wire off the battery and the damned charging unit, which was also sitting on the floor (under 5' of water for 8 hours) starts BEEPING.

How the heck does that happen? I would have thought the water would have shorted everything out and at least tripped a breaker... Not to mention the electronics in the charging unit.

Follow-Up Postings:

RE: Unbelievable!

Water is a very poor conductor of electricity. Many impurities in water act as electrolytes which do render the water more conductive. One must assume that this water had few electrolytes.

RE: Unbelievable!

The cleaner the water the less it conducts.

Water can be used in high voltage discharge machining as an insulator.

De-ionized water does not conduct well at all.
It is solutes dissolved in the water that make it a much better conductor.

Our outer skin layer is dry (dead) ad actually a rather poor conductor.

Once you get past tat barrier the salt content of the rest of our living the cells in our body makes us a decent conductor.

Very good at higher voltages.

Electricity will flow in all available paths based on their impedance.

The lower the impedance the more current flows in that path.

A running pump motor may have a low enough impedance to take so much of the current (and you impedance was high enough) that you felt nothing.
It is not a gamble you should take lightly.
Folks drown in electrified water when they can no longer keep their head above the water and breath.

The electricity flowing though the water and the person can effectively paralyze muscles.

Insulation can still works though.

A set of chest waders may protect you if standing in electrified water.
You will know it is not working when you feel some of the electricity stating to flow through your body, hopefully soon enough to back out and not stumble and fall in.

Skin that has been exposed to water and absorbed some no longer has a high insulation value.

If you want a simple demonstration of how well your skin works, touch a 9 V battery to your dry skin.
You should will feel nothing.

Now touch the tip of your tongue to the two battery terminals at the same time.
You will feel the few mA of current the battery can deliver because the saliva on your tongue has lots of dissolved ions.

All in all it sounds like you got VERY lucky.

I would not repeat the same basement experiment again expecting identical results.

RE: Unbelievable!

This is proof that water DOES NOT short things out and trip breakers.
I have seen full 200A main-breaker panels completely submerged and working just fine.

RE: Unbelievable!

If the water is dirty enough (especially with ions, think about salt water) it can cause problems.

We had a couple of people killed swimming in a lake near a dock that turned out to have some defective wiring.
Apparently they tried to get out of the water when they felt the electricity by using a ladder on the dock (after jumping in from the dock).
As they swam closer to the ladder and dock (the obvious place to exit the water) the current became high enough to interfere with swimming.

Both drowned.

This post was edited by brickeyee on Sat, Apr 20, 13 at 21:50

RE: Unbelievable!

I have to say that it's certainly been a learning experience for me. How many times have we all heard that water and electricity don't mix? Now I'm not suggesting anyone stop exercising due caution but it sure surprised the heck of out me.

Now if we can just get the darned basement dried out...

RE: Unbelievable!

PURE water and electricity are one combination tat is not all that bad.
The problem is knowing the water is pure enough and keeping it pure enough to be an effective insulator.

In some installations (like particle accelerators) deionized water s circulated in transformer windings (the winding are made of copper tubing) to allow for adequate cooling.

By using deionized water a single cooling header can easily feed both primary and secondary of the transformers with the non-conductive water.
Luckily the primary voltages are often rather low (often under 100 V) but the currents (especially on the secondary side) can be VERY high.

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