Hey Dave,
For what it's worth, we looked into the pentair in-line carb unit and if I recall correctly they claimed an approximate max pickup of 1 volume of co2. Before we went forward with the unit, we tried running our longest carbstone (24") in a long spool + tee setup coming right off of our pump and found we can usually get around .7 volumes of pickup during transfer. This was close enough for our needs that we no longer could justify the expense for the unit. YMMV, happy to answer more specific setup questions.
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Rob Schwarz
Storm Peak Brewing Co.
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