When I climbed under the house over the weekend to adjust my water pressure
regulator, I traced the cold water supply line from the point that it enters the
crawl space. The plumbing in my house is copper, but it connects to some sort of
plastic pipe before it connects to the town's supply line. That means that there
is no solid cold water electrical ground.
The problem can easily be remedied by adding a jumper around the plastic
portion, but I could not see well enough to determine whether the pipe coming in
from the street was metal. The line was installed 22 years ago. Isn't it likely
to be metal? I'm probably going to call the town to inquire.
The plumbing in the house was replaced in 1999 because we had Quest pipe, so I
trust the plumbers did the right thing connecting to the town supply.
22 years ago, plastic (pvc/cpvc/black plastic) was in common use.
Grounding to the water supply line is not an approved method. The
proper fix is to install a ground rod or two (depending on your
As per Harry K's comments......the waterline is something not to be
depended upon for a grounding option.
In the old days when supply likes were either galvanized steel or
copper, your main water line from street to house made an awesome
But what happens if that's your only ground & some unknowledgeable
person replaces it with plastic? That's the problem with something
that serves a dual purpose.
The main purpose has to be addressed, the secondary roles can be
Since the introduction of plastic as a main water line material, metal
piping went from a convenient reliable grounding means to a potential
hazard. Ungrounded (unbonded) metal waterlines in a house that get
inadvertently energized could fail to blow the breaker and thus
represent a shock hazard.
A modern grounding / bonding system relies on multiple means .....like
using "a belt, suspenders, duct tape and staples" approach to holding
up ones pants.
A metal waterline (when present) makes a great ground & should be
bonded to grounding system
(best bet is multiple ground rods or a UFER ground which is a major
PITA to do on an existing home).
I've driven a few ground rods and have never gotten a single one to
pass the 25 ohm test.
So I drive multiples but never tested the multiple ground rods in
Most plumbers are not electricians.....I would double check what they
did wrt to grounding system.
Where the water service pipe is at least 10 ft of metal in the ground it
is REQUIRED to be used as a grounding electrode. The NEC has had this
requirement since 1777.
Since metal water pipe may be replaced with plastic in the future, a
"supplemental" electrode is required. A ground rod (or rods) were
commonly used. (Ground rods are close to a joke.) The NEC has actually
required a "supplemental" electrode for a long time if the water pipe
*may* be replaced. More recently it is required for all new services.
For *new* construction the NEC generally requires a "concrete encased
electrode" (commonly called a Ufer ground). This is a good electrode,
and also serves as the "supplemental" electrode. The grounding electrode
system may consist of multiple electrodes.
If the water service pipe is plastic, metal water pipe in the building
is required to be "bonded" to the ground system. The required method for
bonding is not quite the same as for a water pipe that is a grounding
The purpose of "grounding" to the water line is NOT to provide anything to
the electrical service. The purpose of grounding to the water line is to
protect the user from the water pipe, that is, to keep the pipe at the same
potential as a real ground.
In fact, making the service ground a water pipe is illegal in some
In your case, to be safe and legal, make sure both your electrical service
and your metal pipes are attached to separate ground rods.
And in other jurisdictions (such as mine) it is not only accepted as the
ground, it is expected to be. All the service entrance lines have to be
copper if replaced, and the water service line IS the ground in all the
Doesn't seem right. My understanding is that the natinal electric
code bans it. In your jurisdiction, what do the people on well
systems do? I doubt that there has been a well installation made in
the last 30 years that used copper or galvanised for the supply line.
Hard to understand where this delusion, expressed by 2 or 3 people in
this thread, comes from.
The NEC clearly REQUIRES metal underground water pipe to be part of the
grounding electrode system. While details have changed slightly over the
years, the basic requirement goes back a very long time.
The requirement is, of course, for metal underground water pipe (10 ft
or more in contact with the earth).
250.50 Grounding Electrode System
All grounding electrodes as described in 250.52(A)(1) through (A)(7)
that are present at each building or structure served shall be bonded
together to form the grounding electrode system.
250.52 Grounding Electrodes
(A) Electrodes Permitted for Grounding
(1) Metal Underground Water Pipe.
A metal underground water pipe in direct contact with the earth for 10
ft or more (including any metal well casing bonded to the pipe) and
electrically continuous (or made continuous by bonding around insulating
joints or insulating pipe) to the points of connection of the grounding
electrode conductor and the bonding conductors.
So it is another of those urban myths apparently. As for the 10ft
requirement. That is not clear in the above. to me it says _if_
there is 10 ft of metal pipe it can be used. In my well system
installed in the 90s, I _know_ there is no 10ft of metal pipe. At
most it runs 5 ft out from the foundation and connects to the usual
black plastic. The electrical service to the well was installed by an
electrician and runs in the same trench.
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