So you talked about increasing tank(s) volume in future by adding tankage in attic ? I think?
If so, I still say keep out on CL and FBM for newish comp cheap w bad pump.
I keep seeing them regularly, and I also live rural w/o many choices.
Only thing w that is- It will be 99% for sure a vertical 60 that you find... and being vert w drain at bottom, will not lay down in low attic.
Just thoughts.
Marc
My thought was actually multiple smaller vertical tanks. Have to get it into the attic through a small hatch so a 60 vertical or horizontal would not work. Realistically nothing bigger then a 30 for both the size of the hatch & then being able to carry it to where it would live while walking on the rafters. Anything with a drain at the bottom & then basically hang the tanks & then drop down using only the drain into a larger 3/4" feeder going back to the compressor. Gravity doing its thing the water will all fall back to this tank with a timed automatic drain on it. I figure having one point to drain instead of multiple would be for the better.