Residential plumbing bonding question

Posted by Mark G. on May 29, 2008, 2:29 pm

Good morning.

I appear to have an electrical bonding problem with my plumbing. I am
measuring 60VAC between my kitchen faucet and the kitchen drain fitter. The
problem became evident when I replaced the old PVC drain trap with a shiny,
new metal trap. Goodbye, insulator. Hello, tingle.

Further investigation reveals that the kitchen sewer drop is not bonded to
the water pipes and/or the service ground. The main sewer drop (other side
of the house) is bonded to the water supply pipes. The supply pipes are also
bonded to the service ground at that point.

The simplest solution seems to be to run a short bonding cable between the
kitchen drain line and the nearby supply pipes. I can do this in the
basement underneath the kitchen. Would this be satisfactory? I don't want to
create a ground loop. Perhaps I should run a longer bonding cable from the
kitchen drain line to the point where the service ground connects to the
supply lines? Or is there some other approach I should take (aside from "pay
an electrician to do it?)

Thanks
-Mark

Posted by John Grabowski on May 29, 2008, 4:48 pm

> Good morning.
> I appear to have an electrical bonding problem with my plumbing. I am
> measuring 60VAC between my kitchen faucet and the kitchen drain fitter.
> The problem became evident when I replaced the old PVC drain trap with a
> shiny, new metal trap. Goodbye, insulator. Hello, tingle.
> Further investigation reveals that the kitchen sewer drop is not bonded to
> the water pipes and/or the service ground. The main sewer drop (other side
> of the house) is bonded to the water supply pipes. The supply pipes are
> also bonded to the service ground at that point.
> The simplest solution seems to be to run a short bonding cable between the
> kitchen drain line and the nearby supply pipes. I can do this in the
> basement underneath the kitchen. Would this be satisfactory? I don't want
> to create a ground loop. Perhaps I should run a longer bonding cable from
> the kitchen drain line to the point where the service ground connects to
> the supply lines? Or is there some other approach I should take (aside
> from "pay an electrician to do it?)
> Thanks
> -Mark

60 volts indicates a serious problem. Usually a difference in ground
potential is 2 - 5 volts. You had better call an electrician now.

I'm thinking that there is a problem with your neutral conductor and that
you don't have a very good ground for your service. Another possibility is
that one of your neighbors has a problem with their neutral and the current
is coming through your pipes.

Posted by PeterD on May 29, 2008, 7:01 pm

wrote:

>Good morning.
>I appear to have an electrical bonding problem with my plumbing. I am
>measuring 60VAC between my kitchen faucet and the kitchen drain fitter. The
>problem became evident when I replaced the old PVC drain trap with a shiny,
>new metal trap. Goodbye, insulator. Hello, tingle.
>Further investigation reveals that the kitchen sewer drop is not bonded to
>the water pipes and/or the service ground. The main sewer drop (other side
>of the house) is bonded to the water supply pipes. The supply pipes are also
>bonded to the service ground at that point.
>The simplest solution seems to be to run a short bonding cable between the
>kitchen drain line and the nearby supply pipes. I can do this in the
>basement underneath the kitchen. Would this be satisfactory? I don't want to
>create a ground loop. Perhaps I should run a longer bonding cable from the
>kitchen drain line to the point where the service ground connects to the
>supply lines? Or is there some other approach I should take (aside from "pay
>an electrician to do it?)
>Thanks
>-Mark

Is there a garbage disposal unit in this sink? It may be defective.

Aside from that, you have a serious and potentially dangerous
situation there and I'd recommend (even though you don't want to) an
electrican look at it.

You are taking a very real risk that either someone will be injured,
or you will create a fire hazard if there is an inner wall short
between wiring and the plumbing.

Posted by Mark G. on May 29, 2008, 7:45 pm

> Is there a garbage disposal unit in this sink? It may be defective.

No. However, I installed a dishwasher several months ago.
But I changed the drain trap from plastic to metal at the same time,
which bonded the drain fitter to the drain line and allowed me to
discover the problem. So the problem may have been there for some
time and gone unnoticed. I did shut off the dishwasher circuit, and it
had no affect on the problem.

I'm going to try shutting off circuits one at a time, and see if I can
isolate the cause. Failing that, I guess I will need to hire a professional.
*sigh*

Posted by Mark G. on May 29, 2008, 8:55 pm

> I appear to have an electrical bonding problem with my plumbing. I am
> measuring 60VAC between my kitchen faucet and the kitchen drain fitter.
> The problem became evident when I replaced the old PVC drain trap with a
> shiny, new metal trap. Goodbye, insulator. Hello, tingle.

I did some troubleshooting and found the source of the voltage (actually
40VAC,
not 60). Somebody (not me) installed an outlet in the upstairs bedroom and
spliced it into an existing knob-and-tube circuit. Then they grounded the
box to
the kitchen vent stack in the attic. I removed the ground wire, and that
eliminated
the stray voltage in the kitchen. So now my outlet is a two-conductor
ungrounded
(like most of the outlets in the house, on the old KT circuits.) The outlet
appears
to work fine.

But I really don't understand why there would be voltage coming off of the
ground
on the outlet box. Should I be looking for a fault in the outlet?

Thanks
-Mark

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