Old ground is just a wire to cold water pipe?

[joeblow]

I've been tracing the "old" ground wire from the entrance panel at my house (built in the late 70's) and it seems that it is simply a #4 conductor that goes only to the cold water pipe where it enters the basement. Total run is about 45 or 50 feet. Did this ever meet the NEC? I know that current code requires ground rods bonded at the entrance, but I'm surprised at the skimpiness of the old system (even though after reading the NEC I am now very aware of the importance of bonding to the cold water pipe.)

After a number of recent lightning hits taking out DSL equipment, I want to supplement this ground with several ground rods physically near the AC entrance and Telco Demarc. (Luckily the Telco Demarc is at the AC service entrance...). One way to do this seems to be adding a new conductor from new ground rods that goes to the ground in the entrance panel, is this correct? My reading of the NEC leaves me with the conclusion that it is not allowed to cut the existing #4 running to the cold water pipe. I'm wondering if a Cadweld to the "old" #4 wire underground may be allowed or even superior. Are cadwelds forbidden in some jurisdictions for residential grounds? My local electrical inspector didn't even know what I was asking about.

Is it part of NEC code that the hot water pipes be electrically bonded to the cold water pipes too, or just common sense? My look through the book didn't turn up a relevant section.

[Mark or Sue]

Yes.

Ground rods aren't always required, but for most people they are. If all you have is the water pipe, then you need two 8' rods.

Yes, and this is how you should do it.

You have to use non-reversible connections to the grounding electrode conductor, and welding is specifically permitted. But why bother? Just leave that #4 to the pipe alone and run a new #4 from the same bus bar to your rods. You can run as many ground electrodes as you want from the service panel.

It is in the bonding section of article 250. All interior metallic piping that could become energized must be bonded. What could be energized is at the descretion of the inspector. Metal drains usually no, unless you have a disposal. Hot water pipes yes because of the water heater. Interior gas pipes yes because of the furnace and may dryer and/or water heater. The easiest thing to do is just put another clamp on the hot water pipe and see if the cold water bonding wire can reach both pipe clamps. Otherwise, you'll need another clamp on the cold and run at least a #10 copper between hot and cold.

Another change made recently is if your cold water pipe is also a grounding electrode (i.e. it is metal outside for at least 10' in the earth), then your #4 wire to the pipe must be attached within

5' of where the pipe enters from the outside.

-- Mark Kent, WA

[joeblow]

We just had the water heater replaced last year, and I notice that the pipe fittings for both cold-in and hot-out have lots of Teflon tape on them... probably meaning that there's not a good bonding. A trip to Home Depot and $6 later, everything seems to be ship-shape.

Does a plumber doing a water heater replacement have any obligation to check for compliance with current NEC, or does the NEC at the time of original installation set the standard? I'm not going to go out and sue him or anything, I just want to know if I should be generally aggressive to make sure I'm with the latest and greatest code, not just whatever was in effect a quarter-century ago.

Tm.

[j j]

I just got a new main , the ground conductor is connected to two things: the large aluminum cable that holds the utility wires up in the air, and the place where the main water pipe enters the basement. The electrician specifically asked me where the water pipe comes in the house. I guess there's a reason they put it there.