My 1970 house with slab foundation originally had a connection to the copper water line as the only ground. I had a pair of ground rods 6' 6" apart added and would like to disconnect the ground to the copper water supply pipe. Is this allowable and advisable?
The reason I would want to do this is to save the water pipe from damage. We had 20 pinhole leaks in a vertical vertical hot out from the hot water tank. This tank was sweated copper tubing all the way to the tank (advice from city plumbing inspector 25 years ago) instead of flexible supply lines with insulating connections.
There is at least the possibility that the pinhole leaks were due to electrolysis from dissimilar metals (steel tank-copper water lines). Twelve years ago I had the tank replaced with a tankless heater connected with insulated ("dielectric" connections). I want to eliminate the possibility that the ground rods might produce a similar effect in the copper tubing.
Also, I have heard of lightning strikes damaging copper water lines if the panel is grounded to the copper pipes.
If it is OK to disconnect the ground wire to the copper water supply line, should I do this in the panel and at the pipe? Is it OK to leave the old ground wire in place in the panel but disconnected from the ground bar?
Best Answer
No -- that bond wire could save your life!
It is very important that all non-current-carrying metal, including the cold and hot water pipes, be bonded to the electrical system ground. This prevents highly unpleasant surprises should a wire in the dishwasher come loose and contact a water pipe! Furthermore, this requirement is enshrined in 250.104(A) of the Code:
Also, the pinhole leakage you saw in your hot water pipe is a water chemistry issue (excessive chlorine residuals can attack copper pipes), not an electrolytic corrosion issue, and has nothing to do with the bonding of the water system or any dissimilar metals -- in fact, in an iron-copper couple, it's the iron that corrodes first.