Tom,
Most regular propane refilling stations can refill your tank while you
wait. The tank exchange is convenient for them as they can fill many
tanks in one period. They usually offer propane in them slightly cheaper
if you don't take their time up for one refill and just exchange the
tank. It only works for regular commercially available tanks like the
one on your barbeque or camper or forklift, *not usually* the exotic
specialty tanks like fiberglass or aluminum - at least not around here.
Red