Water pipe grounding

[carterjs]

I have copper pipe throughout the house, but the incoming copper pipe is connected to a galvanized pipe sprinkler system through an insulating union. My electrical ground uses the copper pipe as the grounding electrode. In order to improve the grounding, can I use a copper wire to jump across the union, thereby connecting the copper pipe to the galvanized pipe? If I do this, will the pipe still be protected from corrosion?

[Jerry Peck - Codeman]

[carterjs]

It's a lawn and garden sprinkler system, all made with 3/4" galvanized pipe. Most of the pipe, and there must be about 100 feet of it, is buried and not wrapped in tape. Thank you for tackling this question.

[Jerry Peck - Codeman]

Okay, based on the information at hand I am understanding you this way:
- The incoming water service pipe from the city water supply is copper for more than 10 feet (10 feet is the minimum length of metal water piping underground for that metal water piping to be used as a grounding electrode) and this water service pipe is teed off to a galvanized sprinkler pipe, probably teed off outside the structure, then the copper piping continues into the house as the water distribution system piping - correct so far?
- Now back to the tee between the galvanized sprinkler pipe and the copper water service pipe, I am presuming that is connected as follows: copper water service pipe to a copper tee to copper water service pipe to copper water distribution pipe inside the house, with a male (or female) adapter off the copper tee to a nipple to a dielectric union to the galvanized lawn irrigation sprinkler piping - correct so far?

1) The lawn irrigation sprinkler piping goes through an air gap/atmospheric air gap/some type of backflow prevention device before going to the lawn irrigation sprinkler system (this is required to help keep from contaminating the potable water coming into the house).

2) Where is the grounding conductor you are describing connected? Are you sure it is a grounding electrode conductor to the copper underground water piping, or, could that grounding conductor actually just be a bonding conductor bonding the metal interior water piping system to the grounding system?

3) The galvanized lawn irrigation sprinkler system piping is not required to be bonded to the grounding system, however, it would be required to be used as a grounding electrode as all grounding electrodes which are present are required to be bonded together.

4) If the metal water piping is actually being used as the grounding electrode, then it is required to be supplemented by another electrode.

5) Back to your original question regarding the dissimilar metals ... use a brass pipe clamp on the copper piping and a brass pipe clamp on the galvanized piping, with a copper wire between the two clamps. Brass is compatible with galvanized as it has zinc in it as well as being compatible with copper. That isolates the dissimilar contact between the copper and the galvanized and makes the electrolysis path through compatible materials.

Hopefully, that answers your questions and some questions you did not even ask.

[carterjs]

Thank you, Jerry, now all I have to do is find where to buy brass pipe clamps.

Another thing I'm hazy about is whether I have to keep the house upgraded to the latest plumbing, electrical, heating, etc. code requirements, or whether it's OK to maintain it as built as long as there is no new installation. What can you tell me about this?

[Jerry Peck - Codeman]