Sometimes, you might need to "bleed" your sprinkler system. This means you need to remove water from the system and this is something you need to do once a year in order to winterize your sprinkler system. \
Bleed the sprinkler system with a portable air compressor. Turn off all the water to the system and connect the bleed valve for the system to the air compressor. \
Turn on the compressor to send air through the system. You only need to blow the air for a couple of minutes. \
Once the lines are bled, seal off the lines so no water gets in them through the winter. \