Water Line Leak Question

I was asked this question by a customer that buys, fixes and sells or rents out older homes, and I want to get some feed back on this.

Many of the homes he buys are occupied when he buys them. He will buy 1-5 at a time. The homes are 30s-50s vintage with galvanized water supply coming from the street. He has noticed that it seems like many of his homes will develop a leaking supply line, and require replacement, if the home sits empty for an extended period of time (4-6 months). The ones occupied seem to never develope a leak.

The question is will water in a galv. water line that is just sitting tend to be more corrosive than one being used or is it just his imagination and luck.

leak

Not likely, and yes. Most leaks underground develop from the outside in, so the ground is causing the leak, not the water.

If all the empirical evidence points to leaks occurring much more frequently in pipes that have no moving water, I would tend to believe it. Then the question is why? It could simply be that water freezes a lot easier when it isn't moving. And, a frozen pipe will eventually leak. If it never gets that cold in your area, then we'll need an engineering type to figure it out.