Winterization is the process of preparing an irrigation system for cold weather to prevent damage from freezing water. As water turns to ice, it expands by roughly nine percent, generating immense hydrostatic pressure within the system’s closed confines. This pressure can easily rupture PVC pipes, crack brass fittings, and damage delicate internal components like seals and diaphragms. Winterizing the system removes this threat by purging the water before the first sustained hard freeze occurs.
Disconnecting the Water Source
The initial step is isolating the irrigation system from the main household water supply. Locate the dedicated shut-off valve, which is often near the main water meter, in an underground box, or inside a basement or crawl space. Turning this valve completely off ensures that no new water can enter the system during the winterization process or the cold season.
Next, set the system’s electronic controller or timer to the “Rain,” “Off,” or “Standby” position. This disables the automated schedule and prevents the controller from attempting to cycle the zone valves while the water supply is disconnected. Running the pump or activating the solenoid valves without water can cause electrical or mechanical damage.
Methods for Clearing Water from the Lines
Systems installed with manual drain valves at all low points can use the gravity drain method. Opening these valves allows water to exit naturally, pulled downward from the highest elevation points. This method is only effective in systems specifically designed with proper slope and drainage points. Gravity drainage is the safest method for homeowners, requiring no specialized equipment or pressurized air. The drain valves should remain open throughout the winter to allow any residual moisture to escape.
For systems lacking adequate drainage or those in flat terrain, the blowout method using compressed air is necessary. This technique involves attaching a high cubic feet per minute (CFM) air compressor to a fitting located downstream of the backflow preventer or main isolation valve. Exceeding the system’s pressure rating is dangerous and can cause catastrophic failure.
Residential PVC piping is rated for pressures well above the 50 pounds per square inch (PSI) maximum recommended for the blowout process. However, the delicate components within sprinkler heads and zone valves can be severely damaged if the pressure surges past this low threshold. Many professionals advise hiring a certified technician to perform this task due to the high risk of property damage and personal injury. To execute the blowout, the air hose is connected, and the compressor is started only after the first zone valve is opened. Air pressure is gradually introduced, forcing the water out through the sprinkler heads in the designated zone.
The zone should be run only until a fine mist appears, indicating that the bulk of the water has been expelled. Running the compressor for too long after the water is cleared generates friction and heat, potentially melting internal plastic components of the heads or pipes. The technician must cycle quickly through each subsequent zone, repeating the process of introducing air pressure and clearing the water one zone at a time. Begin with the zone located highest on the property and work progressively toward the lowest zones. This approach ensures that water is moved efficiently out of the pipes.
Securing Above-Ground Components
The backflow prevention device (BFP) is often the most vulnerable component because it sits above ground and contains many moving parts susceptible to freezing. After the main lines are cleared, the BFP itself must be drained completely. This involves opening the two test cocks and the two shut-off valves, which allows residual water trapped within the brass or plastic assembly to escape.
In colder climates, merely draining the BFP is often insufficient to prevent damage from ambient freezing temperatures. The device should be wrapped with several layers of insulation material, such as fiberglass batting or specialized foam insulation bags. These materials slow the rate of heat loss from the metal body, offering a buffer against short-term temperature drops. Any exposed piping leading up to the BFP or the main supply line should also be insulated with foam pipe sleeves cut to fit the diameter of the pipe.
Leaving the test cocks on the backflow device open for the winter allows any moisture that collects inside to drain immediately, preventing a pressure buildup if a freeze occurs. Finally, the exposed sprinkler heads should be visually inspected after the blowout. While the compressed air typically clears them, specialty heads like drip emitters or rotary heads may be covered to prevent physical damage from freezing rain or snowplows.