You cannot fill a 500 lb tank with a 20 lb tank. When inverting a 20 lb tank you can fill another 20 lb tank assuming the non-inverted tank has less pressure in it than the inverted tank. A 500 lb propane tank has way more pressure in it than a 20 lb propane tank. Thus making it impossible for the propane in the 20 lb tank to pass into the 500 lb propane tank. Also, inverting propane tanks is very dangerous and should only be done by a professional with the correct hose, tools, and equiptment.

Hope this helps!

-Ben

Tanks 2 You Propane

Propanetanks2you.com