A properly executed fall shutdown prevents the freeze damage that generates the most expensive spring service calls. The blowout procedure requires both the right equipment and the right process, and companies that standardize both across their technician team protect their clients and their reputation throughout the winter.
If you're exploring how to build a stronger sprinkler system operation, our guide on Spring Sprinkler Startup Procedures: A Quality-Focused Field Protocol covers the foundational concepts you'll want in place first.
Air Compressor Requirements for Safe Blowouts
Compressed air blowouts require a compressor with sufficient cubic feet per minute capacity to clear zones effectively without exceeding head operating pressure limits. Typically, a minimum of 20 to 25 CFM at 50 PSI is required for residential systems, with larger commercial systems requiring proportionally more. Using a compressor that is too small requires excessive blow time per zone and may not clear all water from low points. Using one that is too powerful risks damaging poly pipe and head bodies. Documenting the compressor specifications used during each winterization in the job record protects you if a client claims freeze damage the following spring.
Zone-by-Zone Blowout Protocol
Each zone should be blown for 10 to 20 seconds per head, starting from the zone farthest from the compressor connection and working back toward the supply. Running multiple zones simultaneously divides airflow and reduces effectiveness, so each zone should be completed separately. After the initial blowout, cycling through each zone a second time confirms that water has been cleared from lateral lines that may hold residual water at low points. Technicians should never stand over or in front of heads during the blowout, as the air pressure can cause heads to eject with enough force to cause injury.
Controller Shutdown and Client Documentation
After the blowout is complete, the controller should be set to the off or rain delay position, the backflow preventer isolation valves should be closed, and any above-ground pipe or components should be insulated if required by the local climate. A photo of the controller in the off position and the backflow with valves closed attached to the job record creates a timestamped record of completed work. The client follow-up after winterization should include a summary of what was done and a prompt to book next spring's startup, which captures advance bookings while the system is fresh in the client's mind.
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