Here's what one sprinkler manufacturer recommends:
�Use an air compressor with a Cubic Foot per Minute (CFM) rating of 80-100 for any mainline of 2" or less & do not exceed 80PSI on PVC piping,50 PSI on polyethylene piping.
This is what a rental shop supplies or what sprinkler companies use to blow out 99% of the water and vapor from the lines.
Anything less, like a 60 gallon unit producing 15cfm will only remove around 50% of the water. Keep in mind, that water expands by 9% when it freezes. It is possible to leave behind enough water in the lines where it will freeze and cause a break in the line or the sprinkler head.�
However most of our customers do not want to buy such a large compressor just for yearly weatherization. So since blowing water out of lines requires the largest capacity (CFM @ psi) compressor possible. We recommend the compressor that has the highest rating that fits your storage area & budget. More CFM is always faster.