Winterizing a sprinkler system is a preventative measure taken before freezing temperatures arrive to protect the system’s pipes, valves, and backflow preventer from damage. Water expands by about nine percent when it freezes, and this pressure can cause underground components to crack or burst, leading to costly repairs when the system is reactivated in the spring. Removing all water from the irrigation lines is the only way to ensure the system remains intact through the cold months.
Shutting Down Water and Controller Power
The winterization process begins by stopping the flow of water into the system. Locating the main water shut-off valve for the irrigation system is crucial; it is often found in an underground utility box, a basement, or a crawl space near the main water meter. Turning this valve completely off isolates the sprinkler system from the property’s main water supply.
Immediately after the shut-off valve is closed, any drain valve positioned on the supply side should be opened to release residual pressure in the immediate line. This initial depressurization helps to clear the short segment of pipe leading up to the main sprinkler manifold. The system’s controller, or timer, must also be addressed to prevent it from cycling while the water source is disconnected.
Turning the controller to the “off” setting or unplugging it entirely prevents the internal valves from attempting to open a dry line. Running the valves without water can cause them to fail or burn out the internal solenoids, necessitating repairs. Once the water and power are shut down, the system is ready for clearing the remaining water from the underground pipes.
Clearing the Lines Using Compressed Air
The “blowout” procedure uses compressed air to force water from the pipes, which is necessary in regions where the ground freezes, as other draining methods cannot guarantee complete water removal. Proper execution requires specialized equipment, including an air compressor capable of delivering a sustained volume of air, typically 30 to 50 cubic feet per minute (CFM) for a residential system.
Before starting, wearing eye protection is required due to the risk from flying debris and high-pressure air that may escape the system. The air compressor is connected to a designated access point, such as a quick-connect fitting or a drain port, usually located after the main water shut-off valve. It is essential that the air pressure be regulated to a safe level to avoid damaging the pipes and fittings.
For systems built with flexible polyethylene (poly) pipe, the pressure should not exceed 50 pounds per square inch (PSI), while more rigid polyvinyl chloride (PVC) pipes can tolerate up to 80 PSI. Exceeding these limits can cause fittings to separate or pipes to rupture. The procedure involves opening the zones sequentially, starting with the zone located farthest from the compressor to allow the air to travel the longest distance first.
Each zone should be run only until a fine mist appears from the sprinkler heads, indicating that the majority of the water has been expelled. Running compressed air through a dry system for too long can generate heat due to friction, potentially damaging the plastic components, so the air supply must be shut off immediately once the water clears. This zone-by-zone process is repeated, working back toward the compressor, until every section of the irrigation network is clear of standing water.
Securing Above-Ground Components
After the main water lines have been cleared, attention must turn to the exposed components vulnerable to freezing. The backflow preventer, a device typically located above ground, is particularly susceptible to damage from ice expansion. Most backflow preventers have small drain valves or test cocks that must be opened to drain all trapped water from the unit.
Following the manufacturer’s instructions, the valves on the backflow device should be positioned to a partially open or 45-degree angle to prevent water from pooling inside the ball valves. Once drained, the entire assembly should be covered with an insulated blanket or a foam enclosure designed for backflow protection. This insulation provides a thermal barrier against the winter air.
Other exposed devices, such as vacuum breakers and pressure regulators, must also be drained of water and protected from the elements. All sprinkler heads should be checked to ensure they have fully retracted into the ground and no water is pooling around them. Finally, valve boxes containing the zone control valves should be inspected to confirm they are free of standing water and that their covers are securely placed to prevent moisture intrusion and protect the internal wiring.