I'm in an early 50's house in the California Bay Area with galvanized steel pipes in the basement crawl space and an irrigation system that branches off from the house plumbing. I know for sure that the galvanized pipes are at least 18 years old, and maybe they even date back to when the house was built.

The water pressure is fine, and there are no leaks in the house plumbing. There's rust in the water when I first turn it on after I've been away for several months, and there's some rust stain in the toilet.

When I was on the opposite side of the country for several months a year ago, a huge water bill alerted me to a leak. This caused me much consternation until I was able to get the water turned off at the main valve at the house, and determined the water meter at the street was no longer turning. This cut off the irrigation, but fortunately the winter rains were reliable. When I got back I discovered the leak was due to a clogged irrigation valve.

I am soon to be far away again for several months. I don't want the worry of whether a leak will occur in the basement crawl space, but do want to keep the irrigation going. Turning down the pressure regulator at the main house valve low enough to protect the house plumbing may result in deficient irrigation. So I'm considering separating the irrigation system from the house plumbing. That way I can turn off the house water and keep the irrigation available.

But I'm wondering: could vibration from doing this work on the old plumbing in itself cause a leak to develop?