Check The Empty 1 lb Cylinder For Good Condition: Not dented or rusty and that the threads are in good condition.

Chill The Empty 1 lb Cylinder: A refrigerator or ice cooler work great. (about 2 hours will get it chilled.)

Weigh The 1 lb Empty Cylinder: So you know how much propane to add without exceeding the tank's allowable limit.

Thread The Propane Refill Adapter To The Larger Filled 20lb Tank: When you connect the Propane Refill Adapter into the valve of the larger tank, remember it has left-handed threads and be sure to tighten firmly.

Connect The Empty 1 lb Propane Cylinder To The Propane Refill Adapter: Be careful not to cross-thread.

Invert The Connected Propane Tanks: Set on a flat surface.

Very SLOWLY Open The Larger 20lb Tank's Valve: You should hear the transfer of propane taking place.

Listen For The Transfer To Stop: Which will happen when the pressure in both tanks is equalized.

Turn Off The Larger 20lb Propane Tank's Valve: Close the larger tank's valve and turn the tanks right-side-up.

Remove Both Propane Tanks From The Adapter.

Weigh The 1lb Propane Refilled Cylinder: Make sure you have not exceeded the max-rated capacity of the 1 lb cylinder. (To calculate the net propane weight, subtract the empty weight from the new refilled weight. Each model is different so check with your manufacturer for specific details.)

See our post, How To Refill 1 lb Propane Cylinders, Tanks And "Disposable" Small Camping Propane Bottles, for detailed instructions and photos.