How hard is it to clean a liquid propane tank? I never converted one to compressed air before. Thanks 
Open the bleeder valve and pump air into it once it’s empty?
Just make sure you don’t over pressurize it.
-Kris
They are generally pretty highly rated pressure wise. I’ve been told to run water through it as lpg is heavier.
Thanks 
Will do. I am picking up 2 25 Gallon Propane Tanks Friday off of a local “Buy Sell Trade” Facebook Site.
I see you are running pretty normal pressures consider a twin head compressor to speed up fill times. The viairs are tanks but pretty slow.
Going to be going either with an Oasis or a York under the hood.
That would do the job rather nicely.
I have converted a propane tank to a air tank, it is actually pretty easy, I have attached a link to a video that helped me out when I did this the first time.
Just a heads up, i have probably filled and emptied my propane tank with air about 15+ times and the propane smell is still there, so keep that in mind that it will tank A LONG time for it to go away.
link to a video about how to do this