Winterizing an in-ground sprinkler system involves the precise process of removing water from the irrigation lines (a “blow out”). This maintenance task is necessary to protect the system from the significant damage caused by freezing temperatures. Failing to properly winterize can lead to extensive and costly repairs in the spring. The key to protecting your investment lies in understanding the local climate and acting before the first sustained deep freeze.
Establishing the Critical Timing Window
The appropriate time to shut down your sprinkler system is directly tied to local weather patterns, specifically the prediction of the first hard freeze. A hard freeze is defined as temperatures dropping to 28°F or lower for several consecutive hours, which is cold enough to cause water in sub-surface pipes to turn to ice. Winterization must be completed before this event.
To determine the ideal window, consult historical weather data for your region to find the average date of the first hard freeze. Aim to winterize at least one week before this historical date, allowing a buffer in case of an early cold snap. This timing usually falls 2-4 weeks after the last required watering date for the season. Monitoring extended forecasts for nighttime temperatures consistently below 32°F is the most reliable current-year indicator that the time for winterization is approaching.
The Consequences of Delayed Winterization
Skipping or delaying winterization leaves water sitting in the pipes, which expands by about nine percent when it freezes. This expansion generates immense pressure that the irrigation system components are not designed to withstand. The result is often burst PVC pipes and cracked fittings, which require excavation and replacement. Freezing can also cause irreparable damage to the backflow preventer, a device that keeps irrigation water from flowing back into the clean drinking water supply. Backflow preventers are complex and expensive components that are particularly vulnerable to ice damage, often requiring full replacement. Additionally, water trapped inside the plastic housings of sprinkler heads can freeze, cracking the mechanism and rendering the head useless until it is swapped out in the spring.
Preparing the System for Shutdown
Before the physical process of water removal begins, several preliminary steps must be completed to isolate the irrigation system. First, locate and turn off the main water supply valve dedicated to the sprinkler system. This valve is typically located near the water meter, sometimes in a basement or utility closet, and is the only way to prevent new water from entering the lines. Once the water supply is shut off, briefly run a zone on the system to relieve any residual pressure in the main line. Finally, set the irrigation controller or timer to the “off” or “rain” setting. This prevents the system from attempting to cycle and activate the valves while the main water supply is disconnected, which could cause internal damage to the valves.
The Essential Steps of Water Removal
The most effective method for removing water depends on the type of system installed. Some older or simpler systems use manual or automatic drain valves installed at the lowest points of the piping network. Opening these drain valves allows gravity and residual water pressure to push most of the water out of the lines.
Compressed Air Blowout Method
The compressed air blowout method is the most common and thorough technique, especially for underground systems in northern climates. This process involves connecting a specialized quick-disconnect adapter to the system’s blowout port and using an air compressor to force all remaining water out of the pipes. Safety is paramount during this process, requiring eye protection and strict adherence to pressure limits, typically 40 to 80 pounds per square inch (PSI), with lower pressure recommended for polyethylene (PE) piping.
The compressor should be started slowly, and the zones must be cycled one by one, starting with the zone farthest from the compressor connection. Each zone is allowed to run until only a fine mist is ejected from the sprinkler heads, indicating that the bulk of the water has been removed. It is important to move quickly through the zones to prevent the friction from the compressed air from overheating and damaging internal system components. Once all zones have been cleared, the air compressor is disconnected, and any remaining air pressure is released from the system by opening and closing the backflow device valves.