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Follow the hookup procedure
Close off both valves on the backflow preventer. Then remove the plug on the
blow-out port and screw in a quick-connect hose adapter. Snap on the air
hose and connect the other end to the compressor.
With a basic quick-connect coupling, you can use your air compressor to clear water from your sprinkler system for the winter. Just be aware that even the largest home compressor isn't powerful
enough to blow out the entire system at once. But you can probably
blow it out zone by zone.
If you're into number crunching and you have the original irrigation
layout showing the gallons per minute (gpm) of each sprinkler head,
just divide the total gpm of each zone by 7.5. That'll give you the cubic
feet per minute (cfm) you need to blow it out. Otherwise, just rent a 10-cfm compressor and hose from your local tool rental center.
Set the compressor air pressure regulator to a maximum of 80 psi for
rigid PVC pipe systems, or 50 psi for flexible black polyethylene pipe.
Then turn off the water supply and set the system timer to open just
one zone. Next, open the manual drain valve at the end of that zone (if
equipped). Then, connect the air line to the blow-out port as shown. Connect the other end of the air hose to the compressor
and blow out the line. The heads should pop up and spit out water.
Disconnect the hose as soon as they run dry. Don't overdo the blowout—without water cooling the plastic gears, they can melt in less than
a minute. So move on to the next zone and allow the heads to cool.
Then go back and blow out each zone a second time.