This should probably be split off by the moderators as it’s a hijack of the thread:
The answer to your question FLip is that it is not an ideal situation. I built a hangar 20 years ago on top of an unknown LPG line. That hangar is at the west end of my residence, and both are on the top of a hill but on edge of the beginning down-slope. This means that in downpours when the ground is already soaked quite a bit of water builds up, and once every other year a virtual river 2-inches deep would run through the breezeway of my house.
So I ran an east-west french drain across the front of my house which solved the problem by taking the water around both ends of the house, but after building the hangar, water would build up over at the west corner of the house because the hangar acted as a “dam” and channelled increased flow at that juncture. To alleviate that, I hired a guy with a backhoe to dig a french drain between the house and hangar, with perforated pipe inside it, and filled with river-rock, ... that drain connects to the previous east-west drain.
But while digging that trench he hit the hidden LPG line which ran from my 500 gal tank (NW of my house and behind the hangar). That line ran from the tank due south, then at a point beneath the new hangar, turned 90-degrees east along the front of my east-west house.
With the tank where it is NW of the house and N of the hangar, the only way to get the house re-connected to that tank was to run the line between the house and hangar, at the bottom of that new french drain, and connect it to the original line along the front of the house.
The Home Despot guru insisted that only black iron pipe should be used for propane and that it should be fine within that drain, after-all (he pointed out) the original line we hit was black-iron and was just fine after 60 years. (This house was built as a corporate hunting-lodge in 1950.)
Consulting with a civil engineer has resulted in replacing the line with HDG coated with asphaltic tar, designed for submergence. He also pointed out that galvanized pipe is fine for propane as long as modern flame-flue devices are used (heaters, stoves, etc.). The original steam radiators were removed when we remodeled in 1995 so the early-days concerns of “flaking” zinc blocking burners no longer exists, not only for the modern appliances but also because of modern galvanizing methods reduce flaking.
This discussion of zinc and high-sulfur diesel brought this to mind, and while on the subject I notice that virtually every diesel-fuel tank setups seen in the back of pickups and on top of gravity-tanks on the ranches around here use galvanized pipe fixtures. My diesel setup (using an old propane tank) does as well, but these days it’s only ULSD and has a good filter on the tank outlet and another on my tractor fuel system. I doubt it will ever be an issue.
