There should never be water in the propane lines.
Assuming you purge the air out of the line by lighting a burner on your stove, How is the moisture going to get in there to condense out. I mean line is full of PROPANE not AIR. Thus there should be no moist air in the line and no way for water to enter
However there is oil that sometimes gets mixed with propane, and there are chemicals intentionally added to propane to make it stinky.
How water woudl get in that line, however, i don't know
If you suspect water in the line, have a professional propane service (not a filling station but the kind of place that sends the truck out to re-fill the filling station) inspect the tank, and you might want them to go over the rest of the system too.