[Greenbuilding] copper pipe and underground propane leak

[Reuben Deumling]

Two years ago I buried a 45' copper line from my propane tank through the
foundation into my crawlspace. The line was two feet below grade. Yesterday
I discovered 120 gallons of propane missing from the tank, and was able to
isolate the leak to the underground portion of the plumbing. I replaced the
line with 3/4" black pipe wrapped in the PVC tape (yuck) meant for such
purposes. I also was advised to use dielectric unions at both ends where the
pipe enters the ground. I suspect this should take care of matters...

My question is whether anyone on this list has heard of a big leak like this
(~1gal/hr) developing suddenly underground? Our soil shrinks and swells a
lot over the course of a year, and the only thing I can think of is that the
movement of the soil somehow caused the line to pinch or kink or something?
And no, there was no joint below ground. I had used a 50' roll of the soft
copper (whatever letter the heavy-wall variety is). We also have a
seasonally high water table.

Reuben Deumling