How do you check your water quality with an electrical meter

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Eddy Current

Senior Member
Ive heard you can use an electrical meter instead of buying one of those testers that are sold in stores but what is a good reading?
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Are you thinking that current on the water pipe is affecting the water quality. I have heard that can be the case so you would have to find where the current is coming from.
 

USMC1302

Senior Member
Location
NW Indiana
If you're using a typical multi-meter to determine water quality parameters, in this case conductivity, you probably need to consider what the accuracy of your results will be. Google it, and I'm sure there will be a way to calculate using known volume of water, etc. Just depends how accurate you need to be
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
121206-0812 EST

Eddy Current:

I have no idea what you are talking about. There are many aspects to water quality. What do you want to check?

The electrical conductivity of water is one possible measurement. Another would be some measure of the biological contamination of the water.

Turbidity is another test, and would be performed with light and and a photocell. This could be by obscuration or reflection.

An example: I was looking for some distilled water. In the Yellow Pages I found a local company that that claimed to have distilled water by virtue that distilled water was in their advertizment. I went to their plant to get a gallon sample. There they told me that their water was filtered, but was as pure as distilled water and laboratory tests showed no difference. I bought a gallon. Took it home and tested it with my conductivity meter. It was nothing close to distilled water. They totally lied when claiming it was comparable to distilled water.

Absopure distilled water from the grocery store does test like one would expect from a sample of distilled water. It should be noted that distilled water when exposed to air has a very slight conductivity resulting from CO2 from the air being dissolved in the water. Also Absopure filtered water from the grocery store had less conductivity than the water from the local supplier, but higher than distilled water as would be expected.

I tested filtered water from another store where they have an in-store filter machine. Its conductivity was quite high. In other words their filters needed replacement.

I do not know the procedures for biological testing of water. But these tests are not an electrical test.

When doing conductivity tests of water you should use AC or quickly switch the polarity of a DC ohmmeter. A Simpson 260 is easy to switch polarity. A strictly DC test has a polarization problem. Stick two ohmmeter leads in a glass of tap water and you will see the reading increase with time. Obviously the probe tips need to be at a fixed spacing and fully immersed. Better to use a commercial conductivity probe.

See http://en.wikipedia.org/wiki/Purified_water

.​
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
Conductivity or it's inverse, resistivity can be a measure of water quality. De-ionized (DI) water is the purest you can get commercially and it has a resistivity of 18.2 megohms per centimeter. You can't acutally buy it, it has to be produced at the point of use. If you stick a meter in a fresh container of DI water open to the air, you can watch the resistivity drop as you walk across the room to your lab bench as the water absorbs CO2 from the air.

Conductivity can be used to measure total dissolved solids in water. Once you get above about 1,000 micrograms per ml (IIRC), the meter response drops off and it's more difficult to determine incremental increases.

Note that all this is "per centimeter". You can't just stick your Fluke 77 leads is a glass of water and get useful information. Resistivity meters and TDS meters are relatively cheap; as little as $20.
 

tom baker

First Chief Moderator
Staff member
I work for a large water utilty. The people that determine water quality are enviroment techs and the do not use an electrical meter. Water Paramaters such as turbidity, chlorine residual, PH, etc, are all tested using specialized meters. Some tests are very specific and samples are taken to a testing lab.
 

Eddy Current

Senior Member
If you're using a typical multi-meter to determine water quality parameters, in this case conductivity, you probably need to consider what the accuracy of your results will be. Google it, and I'm sure there will be a way to calculate using known volume of water, etc. Just depends how accurate you need to be

Bingo! but I couldn't really find anything when i Googled it, just a bunch of links on how to check your water meter at your house.
 

USMC1302

Senior Member
Location
NW Indiana
I tried to Google after I made that comment. I did find an explanation of how to do it. If I look again, I'll post the link. Again, consider the accuracy of the results.
 

brad9m

Member
Location
Alpharetta, GA
There are a lot of things that you won't be able to determine with a multimeter. Even if you can get conductivity, with some fair amount of accuracy, you will still not have any indication of pH, TDS, bacteria, which metals are in the water, etc. The conductivity measurement alone won't tell you what is in your water.
 

Eddy Current

Senior Member
Yeah i knew it wouldn't give me all the true readings but i was just wondering what to look for to give me some kind of general idea if the water is good/bad.
 

hurk27

Senior Member
I know most of this has been said, detecting conductivity of water only tells you that there is conductive minerals in the water, but what this wont tell you is what is in the water that is conductive, it could be lead or other dangerous metals, on the flip side getting a high non-conductive reading could also pose a danger as there are other contaminants that could harm you but are not conductive at all so even if you get a high reading the water could still be unsafe to drink, so having the water tested by a proper lab is the only good way to find out what is really in your water, and make sure this lab test for all contaminants that could cause harm.

In many areas there are free test done if you take them a sample, some water supply company's also offer this service, but be careful as they do not test for everything.
 

iwire

Moderator
Staff member
Location
Massachusetts
Yeah i knew it wouldn't give me all the true readings but i was just wondering what to look for to give me some kind of general idea if the water is good/bad.

You don't seem to be getting it.

Your water could be hazardous regardless of any resistance measurement.
 
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