Originally Posted by tiger
When I disconnected my tanks, a black or very dark brown oilly or tar looking substance is dripping out of the hose.
What is it and Why?
Small amounts of lubricating oil are added to propane by refiners and marketers to prolong the life of pumps and valves used during distribution. Since the oil does not vaporize, it accumulates in the tank over the course of time.
If it's in the hoses it's because some liquid propane got into the hoses at some point. The liquid propane carried the oil along with it and then when the propane vaporized the oil was left behind. This could be a result of the tanks being overfilled, or using the tank in the wrong orientation (vertical tank used horizontally or upside down, for example), or just from propane splashing around while going over rough roads with the fridge on.
The regulator should be above the tanks, and the hoses should slant down toward the tank valve, so that any liquid that accumulates runs back into the tank.
Originally Posted by RickDavis
There is a substance added to LP to give it the distinctive onion odor, This stuff accumulates in the tank over the years and that is probably what you are seeing.
You will also notice you may get some odor from your stove when running on an almost empty tank even though you don't have a leak. \Not sure why it is showing up in the hose
Methyl mercaptan is the substance used as an odorant. Because it boils at 43 degrees F. it will not accumulate in liquid form except in cold weather. Trace amounts present in the lubricating oil may be responsible for any accompanying stink.