Apparently I'm missing something you're saying. I'm going to go through it step
by step and you tell me what I'm missing.
> With out the check valves the first compressor to start will be filling
> both tanks. Depending where the lower one cuts in at the first on can
> override it by filling the other tank and you end up with one compressor
> and two tanks.
This I agree with.
> With the check valves you will only draw air from the one
> with the higher pressure.
Are you talking about a system where the cut in/cut out ranges of the two
compressors don't overlap at all? That's the only way you would only draw air
from just one tank. Otherwise, when the pressure from tank A dropped below the
pressure in tank B, you would start drawing from both tanks.
If I had a two compressor system and was using more air than one compressor
supply, I would want the two cut in/cut out ranges to be as close as possible
(though not exactly the same, for startup power reasons) so that tank pressure
would be maintained at a higher level. If the two ranges didn't overlap,
would only be maintained somewhere in the lower range where both compressors are