Cold Water Supply Line

[mcp6453]

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.

[Harry K]

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 location.

Harry K

[DD_BobK]

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 ground. 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 overlooked.

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 parallel.

Most plumbers are not electricians.....I would double check what they did wrt to grounding system.

cheers Bob

[HeyBub]

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 jurisdictions.

In your case, to be safe and legal, make sure both your electrical service and your metal pipes are attached to separate ground rods.

[Bob F]

In my undestanding, the electrical service and the water system ground must be tied together.

[DT]

The water pipe must be *bonded* to the grounding system, not separate grounds.

[hrhofmann]

Salt water poured on the ground next to a ground rod will lower the impedance, at least long enough to pass an inspection, so I've been told. Never had to use it myself.

[Steve Barker]

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 houses here.

s

[bud--]

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 electrode.

[Harry K]

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.

Harry K

[bud--]

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).

2008 NEC: 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. (end quote)

[bud--]

If there is 10 of metal pipe or more it *must* be used (250.50).

[Harry K]

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.

Harry K