put the 1# tank in a freezer until well cold. turn the 20#r upside down. Wrap the 1# in a towel to keep it cold, screw it onto your adapter and open the valve. If you're luckey you will get in 12/13 oz of propane. I have never gotten much more in so overfilling has never been a problem. Do this outside in the middle of the driveway or something. Away from any possible source of ignition. Never had a problem and never overfilled a small tank.I think the law says something about illegal to refill and TRANSPORT.
