In Northern Virginia and Maryland, the proper winterization technique is the “Blowout”. We highly recommend using a company that is a Certified Irrigation Contractor. Here is what happens during this process:
1) Service technician will use an air compressor with a CFM (Cubic Foot per Minute) of 125-180 and a PSI of 50-80
2) The compressor will attach to the principal water line with an adapter
3) The service technician will close the sprinkler shut off valve
4) Then they will open the Test Cocks on the backflow
5) Now they will open up a valve either manually or by the control box
6) Service technician will slowly open up the pressure of the compressor to begin the “blowout”, pressure shouldn’t exceed 80PSI
7) Technician will watch each zone, preferred to start with the zones farthest away and work closer
8) In general, each zone will take 2-3 minutes until all the water has been released from the zone (it is important not continue blowing air through the pipes after all the water is gone because the pipes will get very hot and it could cause damage