Replies

1. 
   G80104 | Jan 09, 2003 03:32am | #1

   D.

         This is the Cold Water Bonding , should be 5' from where the water service enters the house by code in this neck of the woods . 6ga. copper should run back to the main. Also a ground rod off the main, not jumped from the cold water bond. We also have a UF ground that is ran to a rebar that is  clamped to the foundation rebar. Check with a local electrican to see if yours is ok.

2. 
   CPopejoy | Jan 09, 2003 07:35am | #2

   D-HO,

   If the water supply pipe for your house is metal for at least ten feet underground before it enters the house, Code requires you to use it as the main grounding electrode.  This means you have to use a proper clamp within 5 feet of where it enters the house, and run a continuous grounding electrode conductor to the service panel.  The size of the conductor depends on the size of the service--#4 AWG copper for 200 amp service.

   If the supply pipe is non-metallic, you still have to bond (connect) the metallic interior water piping to the grounding system of the electrical service panel.  You use #4 copper, but you can make the connection to the water pipe anywhere in the house.  I usually bond at the water heater supply pipe in the garage, which is near the service  panel.

   And if the water supply pipe is non-metallic, then you need another type of grounding electrode.  One type is a ground rod, a 1/2" by 8 foot long steel rod, copped-plated.  It's driven into the ground (preferably at the roof eave drip line, where the soil is damp the longest) the full 8 feet.  Code requires two rods unless the resistance of one can be shown to be very low (25 ohms or less).  The equipment to test this is so expensive, it's almost universal to drive two.  The #4 copper is unsed to connect the rods to the service panel.

   Better than the ground rods is a Ufer grounding electrode, which is 20 feet of either rebar or #4 copper wire encased in the concrete of the building's footing.  The Ufer gounding electrode is named after the guy (Mr. Ufer) who invented it to ground bomb storage bunkers in WWII--static electricity and bombs don't mix well, so a good ground is essential.

   As far as testing any of these grounding electrodes, there is a test meter called a "fall of potential" ohmmeter.  Not cheap, not simple to use.  In residential situations, the usual way to confirm a good system ground for the panel is to inspect the clamps and wires, looking to make sure there's no corrosion,  and checking to see that the wire is not damaged and the clamps are tight.  When in doubt, you drive a couple more rods and run another grounding electrode conductor back to the panel.

   So you need to check not just the wire between the water pipe and the ground rod, but most importantly between those things and the service panel or meter base ground/neutral terminal bar.  You may want to look at "Code Check Electrical" by Redwood Kardon, published by Taunton Press.  It explains this using some nice diagrams.

   If in doubt, have an electrician out to check it.  And have them put in some GFIs to boot, or a clamshell cover on the outdoor GFIs, as you'll probably have to pay for an hour of their time anyway.

   Good luck.

   Cliff

1. 
   BossHog | Jan 09, 2003 05:02pm | #3

   Maybe this is a dumb question, but I'm not a plumber or electrician.

   Whay would you be REQUIRED to ground water lines? Doesn't seem to make sense.............I have an answering machine in my car. It says, "I'm home now. But leave a message and I'll call when I'm out."

1. 
   BarryO | Jan 10, 2003 12:42am | #7

   Whay would you be REQUIRED to ground water lines? Doesn't seem to make sense.............

   Aside from the issue of using a water pipe as the grounding electrode, there is also a code requirement ('can't look it up right now; a hard disk crash ate my copy of the code) that requires that metal parts of the structure, which may accidentally become energized (and thus dangerous), are to be grounded.  Metallic water and gas pipes are explicitly listed.

1. 
   JohnSprung | Jan 10, 2003 05:02am | #10

   Barry has it right.  Every sizable hunk of metal should have a direct all-metal connection to the system ground and neutral at the service entrance so that if a hot wire comes in contact with it, enough current flows to trip a breaker.  I plan to ground my copper roof, on the theory that if somebody in the future puts up Christmas lights and nicks some insulation, we won't have the downspouts going hot. 

   If you have metal water pipes running hundreds of yards through the ground, and two driven ground rods, but no other connection between the pipes and the neutral of the electrical system, that probably won't have low enough resistance to trip a breaker if you get a hot touching a pipe.  The required 25 ohms will only pull 4.8 amps, not enough to trip any residential breaker.

   We call it grounding, but it's mainly about making absolutely sure that breakers trip when something goes wrong.  The rods and pipes connecting it to true earth ground is to make sure that we don't get a shock if we touch both the damp earth and some box or conduit or something like that.

   -- J.S.

2. 
   BillHartmann | Jan 09, 2003 06:15pm | #4

   CAP

   "If the water supply pipe for your house is metal for at least ten feet underground before it enters the house, Code requires you to use it as the main grounding electrode."

   I could not find anything in the code (99) that implied that the water pipe would be the main grounding electrode. In fact if the water pipe was only "natural" grounding electrode it had to be suplimented with a an additional electrode while all of the others can stand alone.

   BOSS

   This is case where a small change of wording makes all the difference. The purpose is to ground the electrical system TO (or using) the water pipe. Not ground OF the water pipe.

   However, even if the water pipe is not the ground electrode it is still connected to the electrical system ground. That is called BONDING. The purpose is to make sure that all metal in the home is at the same voltage level.

1. 
   CPopejoy | Jan 09, 2003 08:44pm | #5

   Bill,

   I use the 2002 NEC, and though the format is a little different, the requirements haven't changed. The Code requires a water pipe electrode to be used if it is available. It does not require any additional electrodes to be used. Some AHJs (local bldg depts) may require more than one type of electrode (for instance, an underground water supply pipe and a Ufer), but it's not in the National Code.

   Here is the section of the Code. Note that the water supply pipe is listed first in Section 250.52(A), which most people interpret to mean that it has higher "status" in the pecking order.

   The use of water supply pipes as grounding electrodes is not without controversy--in certain not-so-rare ground fault conditions, there can be significant current flowing on the water piping system. Plumbers have gotten shocked and even electrocuted when they break a supply pipe, and some wetheads are now using electrical jumpers across the section of pipe they are going to open. Until this hazard is dealt with via the code revision process, metallic water supply piping still has to be used as the grounding electrode.

   From the 2002 NEC, copyright NFPA, Quincy MA.

   III. Grounding Electrode System and Grounding Electrode Conductor

   250.50 Grounding Electrode System.

   If available on the premises at each building or structure served, each item in 250.52(A)(1) through (A)(6) shall be bonded together to form the grounding electrode system. Where none of these electrodes are available, one or more of the electrodes specified in 250.52(A)(4) through (A)(7) shall be installed and used.

   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 3.0 m (10 ft) or more (including any metal well casing effectively bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductors. Interior metal water piping located more than 1.52m (5 ft) from the point of entrance to the building shall not be used as a part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system.

   Exception: In industrial and commercial buildings or structures where conditions of maintenance and supervision ensure that only qualified persons service the installation, interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building shall be permitted as a part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system, provided that the entire length, other than short sections passing perpendicular through walls, floors, or ceilings, of the interior metal water pipe that is being used for the conductor is exposed.

   (2) Metal Frame of the Building or Structure. The metal frame of the building or structure, where effectively grounded.

   (3) Concrete-Encased Electrode. An electrode encased by at least 50 mm (2 in.) of concrete, located within and near the bottom of a concrete foundation or footing that is in direct contact with the earth, consisting of at least 6.0 m (20 ft) of one or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars or rods of not less than 13 mm (1/2 in.) in diameter, or consisting of at least 6.0 m (20 ft) of bare copper

   conductor not smaller than 4 AWG. Reinforcing bars shall be permitted to be bonded together by the usual steel tie wires or other effective means.

   (4) Ground Ring. A ground ring encircling the building or structure, in direct contact with the earth, consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 2 AWG.

   (5) Rod and Pipe Electrodes. Rod and pipe electrodes shall not be less than 2.5 m (8 ft) in length and shall consist of the following materials.

   (a) Electrodes of pipe or conduit shall not be smaller than metric designator 21 (3/4 trade size) and, where of iron or steel, shall have the outer surface galvanized or otherwise metal-coated for corrosion protection.

   (b) Electrodes of rods of iron or steel shall be at least 15.87 mm (5/8 in.) in diameter. Stainless steel rods less than 16 mm (5/8 in.) in diameter, nonferrous rods, or their equivalent shall be listed and shall not be less than 13 mm (1/2 in.) in diameter.

   (6) Plate Electrodes. Each plate electrode shall expose not less than 0.186 m2 (2 ft2) of surface to exterior soil. Electrodes of iron or steel plates shall be at least 6.4 mm ( in.) in thickness. Electrodes of nonferrous metal shall be at least 1.5 mm (0.06 in.) in thickness.

   (7) Other Local Metal Underground Systems or Structures. Other local metal underground systems or structures such as piping systems and underground tanks.

   END

1. 
   BillHartmann | Jan 09, 2003 10:01pm | #6

   " If available on the premises at each building or structure served, each item in 250.52(A)(1) through (A)(6) shall be bonded together to form the grounding electrode system."

   That is saying that ALL of those that are available must be used to from the GES. I am not sure how you can say that one of them is the "main" one when all available are required. But in a home the water pipe is the usually the only one that is always there without extra effort.

   In the 99 NEC 250-50 (a)(2) Supplimental Electrode Required. "A metal underground water pipe shall be supplemented by an additional electrode of type ...."

   codecheck.com is not back in service, but the new version needs a lot of work. But I found this;

   "Water pipe must be supplemented (not sole electrode) [50-50a2] {250.53D2}"

   I am not sure, but I think that the 250.53D2 refers to the 2002 NEC. Check it out and let me know.

   I would be very very surprised if they would now allow the water pipe to the the only grounding electrode. The thing being you never know when that 10 ft of metal pipe might be replaced with plastic.

1. 
   CPopejoy | Jan 10, 2003 01:13am | #8

   Bill,

   You're absolutely right, a second electrode is required if a metal underground water pipe is used. That requirement was moved to 250.53(D)(2) in the 2002 Code, and I goofed by not looking further that 250.52.

   Thanks for pointing it out, and my apologies for misinforming anyone.

   Cliff

2. 
   4Lorn1 | Jan 10, 2003 04:26am | #9

   Some months ago I had a discussion with a local inspector. From this conversation I gathered that: Locally the interpretation, with a word that the code is moving in this direction, is that metallic piping is to be grounded but not used as a ground. That is, to the extent possible, any stray currents carried by any piping entering the house should flow to the ground rod or other made electrode system and be dissipated back to the transformer by way of the earth.

   Also, in an ideal case, any currents generated at the house would dissipate through the made electrode not through any piping as this may, personal experience here, be a hazard to anyone working on the piping system. It is not possible, with current accepted residential standards, to totally prevent in-ground piping from acting as a grounding electrode but it can be limited by proper design and installation of the system and low resistance grounding electrode/s.

   The same goes, generally, for the interior piping, gas or water. The pipes are grounded to prevent them from maintaining any potential but are not used as part of the grounding system.

3. 
   billyg83440 | Jan 11, 2003 02:16am | #11

   Been following this with interest. My 25 yr. old house has no grounding rods. Just using the water line. Would it be a good idea to add 1?

   I'll have to check if my gas pipe is connected. I don't think it is. Unfinished basement ceiling easy to check, just haven't noticed.

   Thanks

   Bill

4. 
   4Lorn1 | Jan 11, 2003 02:58am | #12

   If you are presently experiencing no problems adding a ground rod or two would not yield any noticeable change. That said, properly done it wouldn't hurt and may help in any number of fairly rare cases. If ,for example, the pipe needed replacement it might prevent a plumber from getting a nasty shock and maintain an alternate ground path if the plumber should replace a section with plastic pipe.

   Check with your local inspector and/or your gas utility before grounding any gas piping. The only consistent practice with this is that if the gas meter is close to the service equipment it is likely to be required to be grounded to the service equipment to prevent differences in potential and a shock hazard. The sure thing is that the gas line must not end up being the electrode for the system. A spark from a parted gas line conducting a fault current, say from a defective appliance, is likely to end badly.

   Soiled shorts may be the least of the problems. I have only rarely seen anyone move so fast as the gas tech working on the house with the defective ground system. We got called for the electric shower, another story for another day, and were, as luck would have it, on hand for the action.