Winterization prepares an irrigation system for cold temperatures by removing all water from the pipes, valves, and sprinkler heads. This preventative measure is necessary because water expands when it freezes, creating immense pressure that can shatter system components. Homeowners in any region expecting temperatures to drop below freezing must winterize their systems to prevent damage. Neglecting this maintenance task is the leading cause of costly springtime repairs.
Understanding When Winterization Is Necessary
The necessity of winterizing a sprinkler system is determined by local climate and ground temperature, not solely by air temperature. Winterization becomes mandatory where temperatures consistently drop below 32°F (0°C) for extended periods, allowing frost to penetrate the soil deeply enough to reach the buried plumbing. This relates directly to the regional “freeze line,” the maximum depth the ground freezes during winter. Since most residential irrigation lines are installed 8 to 12 inches deep, they are often vulnerable if the freeze line extends deeper. In milder areas with infrequent freezes, only draining above-ground components, like the backflow preventer, may be sufficient. However, sustained cold requires active water removal from all underground lines to safeguard the system.
The Specific Consequences of Undrained Systems
System damage results from the physics of water freezing. When water turns to ice, its volume increases by approximately 9%, generating immense pressure within the closed irrigation system and rupturing components where they are weakest.
The backflow prevention device is one of the most vulnerable and expensive components. Located above ground, freezing water inside the assembly can crack the brass body or destroy internal seals and check valves. Replacing this device is often the most costly repair resulting from a failure to winterize.
Underground pipes, whether PVC or flexible polyethylene, are also susceptible. Expanding ice creates hairline cracks that are invisible until the system is repressurized in the spring, leading to major leaks that require excavation and replacement.
Damage also extends to control mechanisms like solenoid valves and sprinkler heads. Water freezing inside the valve body can warp the housing or damage the diaphragm, causing operational failure. Residual water trapped in the sprinkler head casing can crack the shell, requiring replacement.
The Three Main Winterization Techniques
Water must be removed using a specific technique, which depends on the system design and the severity of the local winter climate. The Manual Drain procedure relies entirely on gravity. This involves opening manual drain valves positioned at the lowest points of the main and lateral lines, allowing water to flow out naturally.
Automatic Drain Method
The Automatic Drain method employs spring-loaded valves installed beneath the system’s low points. These valves automatically open when water pressure drops after the system is shut down for the season. This passive draining allows residual water to escape without manual intervention, though reliability can be compromised if underground pipes shift.
Compressed Air Blow-Out Procedure
The Compressed Air Blow-Out procedure is the most common and effective method for regions with hard freezes. This involves connecting a specialized air compressor to the designated blow-out port, forcing all remaining water out of the lines through the sprinkler heads. This active process ensures the complete removal of moisture from all components.
Blow-Out Safety and Technique
Safety is paramount when using the blow-out method, as excessive air pressure can severely damage the irrigation components. For most residential systems, the air pressure should be regulated and should not exceed 40 to 80 pounds per square inch (PSI). Systems using flexible poly pipe generally require a lower pressure setting (40-60 PSI) than rigid PVC pipe. It is necessary to use an air compressor capable of providing high volume, measured in cubic feet per minute (CFM), rather than simply high pressure. The pressure must be introduced gradually, and the zones must be cycled one at a time, starting with the zone located furthest from the compressor connection. Once water stops spraying and only a fine mist appears, the zone is clear.