ECN Forum Forums Technical Discussion Electrical Theory and Applications How conductive is your water?

There has been a discussion elsewhere about just how conductive household water really is, and whether "pure" tap water will trip a GFI easily if a hot wire contacts it.

One experimenter came up with some very low currents through a cup of water, so I thought I'd try an experiment myself. The piped water in this part of eastern England is very hard and rich in minerals.

Don't try this at home, kids!

Here's my "lab" setup:

Small measuring jug, 8 fl. oz. of cold water. Two conductors stripped and immersed in the water to a depth of 2" and about 3" apart. Power applied: 240V @ 50Hz.

Initial current was measured as 450mA, but started to rise slowly. I never knew water had a negative temperature/resistance coefficient before!

The current reached 1A after 4 mins., and at 6-1/2 mins. the water was starting to boil at a current of 1.2A.

Maybe I should start worrying about the purity of our water!

Final stage of experiment:

We all know that salt water is a better conductor than plain water, right? I never realized just how much more until last night.

Starting with 8 fl. oz. of cold fresh water again, I added a level teaspoon of salt and stirred.

Threw the switch and got quite a surprise: A massive 14.7 amps! Within 10 seconds there was steam from the water around the electrodes and the current had risen to 17A.

The experiment was forcibly abandoned as this point due to a blown fuse in the plug....

LOL! Paul, great stuff! Boy, we're becoming a regular junior-UL between motor-T, Pauluk, and myself! (Did I skip any other mad scientists?)





[This message has been edited by sparky66wv (edited 05-22-2002).]

When I was in the Navy. The aircraft carrier that I was on made thousands of gallons of water per day. The water on the ship was so pure that it was nonconductive. We had received some new ice machines, and when we installed them, for some mysterious reason the machines didn't work. Why? For the above reason. When the ice tray would fill there was an anode and cathode on each end of the tray which would complete a circuit to start the freezing process. With the nonconductive water the freezing would never start.

Regards,
Doc

I'll ring in here, as a service tech many moons ago, a LOT of the switchgear in downtown Wash., DC was mine to service, repair, etc..

I can't tell you how many times I've seen entire 4- 8000 amp gear completely engulfed in rainwater, sewage, water main break, etc..
With only a few exceptions (where it would boil) the switchgear would almost never 'trip out' and had to be de-energized manually.

So for the most part, when someone says water is conductive, I'm likely to say "Really? Where?"

Small technical aside: http://ices.che.ufl.edu/CentralHeatingPackageBoilers/3electrode/Default.htm with respect to a description of: "electrode boilers."

I was thinking about electrode boilers while carrying out my experiment.

They don't seem to be popular any more, but with water as conductive as mine, I reckon they must have worked pretty well.

Paul:
Check out http://www.lindsaybks.com/prod/elec.html
and get these few books.

The first talks about building your own carbon arc torch, and eventually gets to building your own starting resistor out of a 5 gallon bucket of water, so you can use 110 volts to run your arc!

How to Build a Carbon Arc Torch
by Don Meador No. 1349 $6.95

How to Salvage Carbon Rods
by Don Meador No. 3029 $4.50

Design & Build a Water Resistor for Carbon Arcs
by Don Meador No. 1440 $7.95

great fun.
Trainwire


[This message has been edited by Trainwire (edited 05-24-2002).]

[This message has been edited by Trainwire (edited 05-24-2002).]

[This message has been edited by Trainwire (edited 05-24-2002).]

I was able to drive a 100 watt A-19 Incandescent lamp [noticably dimmed] with 120 VAC through a 16 Ounce glass of unfiltered City Tap Water.

Same Lamp became almost full intensity when Salt was added and stirred into the water.

Bubbles could be seen forming on both submerged "Probes", as would be expected with AC.

I would like to try this test with DC [Rectify the 120 VAC] and drive a similar load.
If I do, I'll post results!

In a nutshell, our Tap Water is nearly as conductive as Carbon!!!

Scott S.E.T.

Interesting books. I like this "real experimenter" stuff.

I thought about trying DC as well, but I haven't got any hefty enough silicon diodes handy just at the moment.