On 9/19/18 7:40 AM, George P wrote:
What's the procedure?

Seems simple but I could be missing something.
1) Turn off valve to large tank (250 gallons).
2) Open line (wearing gloves & pointing away from face)
3) Connect the small tank (20 gallons) taking care to prevent air entry

Is there more to it from a safety standpoint than that obvious procedure?

There's a guide here to tank sizes:
https://www.amerigas.com/amerigas-blog/2016/april/tanks-101-propane-tank-sizes
Would putting the 150 gallon one on a small trailer be a practical
option?