Winterizing a sprinkler system with a small air compressor requires blowing out each zone several times.
Letting the compressor build up 80 or so psi before blowing out a zone will provide enough volume of air to evacuate most of the water in the line.
Always let the air compressors build up to full pressure when blowing out each line and stop once the air pressure drops below 40 psi and let it come back up to full pressure.
If you have several zones cycle through each zone allowing water to settle between ‘blowing out’ each zone.
Watch the farthest head on each zone to be sure only a fine mist comes out in the first seconds of blowing out the zone.
As the air pressure drops, quicker the smaller the air tank on the compressor, less water will be evacuated from the line.
Whenever you are in doubt blow out the line one more time, a little water can freeze and cause you to repair the line in the spring.