Resistence and Plastic Water pipes

Can I detect plastic water pipes by checking the resistance of the piping?
If so where and how would I do this?

I’m a little confused about what you’re asking. Are you asking:

  • If you can tell the difference between metallic and non metallic piping with resistance testing?
    OR, are you asking:

*]If you can detect the possible presence of an isolated non-metallic section of piping in a system that visually appears to be all metallic with resistance testing?


Are you saying…how do I determine if I see metal water piping going into the wall…that they did not change over to plastic somewhere and IF it is all a complete run of metal water pipe…is that what you are asking?

Yes Paul.

Any break in the metallic piping will give you the same indication as if it were plastic.

What you are asking, would not be a reliable way to determine the type of piping in the home.

At best, you could check the bond (or lack of bond) at the metallic piping.

If you have the grounding pigtail adapter for your Suretest you could verify the grounding path that way. Just be sure nobody is touching the plumbing when you do.

I’m curious, what is the point?

This is what is swishing around in my snow globe of a brain today:

The NEC, I know this isn’t a code forum, says use the water pipe. Then says if you use the water pipe drive a rod(or a plate, or use rerod, etc). The only time you ‘measure’ anything is when you are checking the grounding path for rods. It is assumed that the water pipe is acceptable if metal(10feet) and grounded to. So the only ‘resistance check’ you need to do is maybe pull on accessible ground clamps. Although I think this isn’t SOP either.


I think he was just trying to figure out a way to determine if the whole piping system was metal or plastic…so to be aware of IF he should bring up any additional bonding issues.

It was a two part question the first part being yes or no, the second part was where I had hoped to spark some theroectical discussion.:smiley:
I guess I’ll play around with my fluke meter and get back to you.

Brian you are nut’s.:smiley:

Love Todd

I would give you a greenie, but allas I am not allowed.

I am up to 158 points though. LOL

I have to go to Scotts dale some time next month to meet with a Builder. Is ok if I call you ahead of time so we can meet for lunch? If so e mail me, or post it here.

480-205-1103 your buyin.:smiley:

Here’s a theoretical question. If water is a conductor and water supply pipes, whether copper or plastic, are under pressure (hence, the pipes should be full of water); theoretically, wouldn’t the system still act as a conductor to ground? :?::stuck_out_tongue:


Believe it or not water is not a conductor. Distilled water has a very high resistance.
Any conductivity in water is due to disolved minerals or other chemicals.

The answer is yes! I do it all the time. I am not an electrician. I am not a plumber.

Go to a bathroom outlet. Turn on your multimeter. Put the black lead from your multimeter into the small (hot) slot in the outlet. Take your red or other lead and put it on the water shut off stub out at the wall. If you read 122, 124, 126 or around there, it’s 99% sure that it’s metal. (cu, galv. etc.) If it reads 35 - 70 or around there, it’s plastic. (pex, PB, pvc, etc.)

I have been doing this for 3 years. I started doing it in houses that I already new what type of pipe it had and the test confirmed it. Then I did the test in houses that I didn’t know the type of pipe, but kept the results in my head, and later confirmed the type up in the attic.

Just try it on a pex house. You will get a low reading. On a old copper or galv. house you will get the high reading.

Mark if you are using an Ampmeter and doing as you describe you would be providing a short circuit path through your meter if the piping is bonded to ground. This would give a nice arc and blow your ampmeter.:frowning:

Are you sure you have described this correctly?:shock:

Ok, whats the meter called with the 2 leads and you set it to conductivity or 600v or all the other settings? Multimeter?

Multi-meters generally have:

Ohms (resistance measfurement-not for energized circuits as it will destroy the meter in most cases)

**Volts (from your numbers above I believe that this is what you are using)

**Amps (for measurment of current)

ok multimeter, I will go back and edit the word ampmeter for multi meter…

You know the pipes in your own house. Try it, you’ll see that it works.

Try it, you’ll like it…