Winterization is the process of completely removing water from your drip irrigation system before freezing temperatures arrive. This procedure is necessary because water expands by about nine percent when it freezes, creating immense internal pressure within the system’s narrow pathways. That expansion can easily crack the thin-walled tubing, split plastic fittings, and damage the small, delicate internal mechanisms of emitters and control devices. Draining and clearing the system protects your investment from expensive repairs and ensures the components remain functional for the next growing season.
Shutting Down the Water Source and Disconnecting Components
Locate and turn off the primary water supply feeding the system, which is typically a garden spigot or a dedicated main valve. Once the flow is stopped, address the head assembly, which is the collection of components connected directly to the water source. This assembly includes the backflow preventer, pressure regulator, filter, and often a hose-end timer, all of which are highly susceptible to freeze damage.
These components contain small internal parts and trapped moisture that cannot be reliably cleared by draining the lines alone. Carefully unscrew and disconnect the entire head assembly from the water source. If your system is controlled by a timer or controller, switch it to the “off” position to prevent it from cycling and reintroducing water.
Gravity Draining the Main Lines
With the water supply secured and the head assembly removed, the next step is to drain the bulk of the water from the tubing using gravity. This is accomplished by opening all manual flush valves or removing the end caps at the lowest points of your main drip lines and manifolds. Water will naturally flow out as the system depressurizes.
You can help encourage drainage by gently lifting sections of the tubing that may have sagged, especially in low spots where water naturally pools. While this passive method removes the majority of standing water, it is rarely sufficient for complete winterization. Residual moisture remains trapped in the low points, curves, and within the emitters, which is why a more active clearing method is required.
Using Compressed Air to Clear Residual Water
The most thorough method for ensuring no water remains is to use compressed air to “blow out” the lines, forcing out residual moisture. You will need a portable air compressor and a blow-out adapter that connects the air hose to the system’s mainline. Wear eye protection to guard against flying debris and water.
Before connecting the air, ensure all end caps or flush valves are open at the farthest points of the system to provide an exit for the water. The pressure setting on the compressor is critical; for drip irrigation components, the pressure must be set to a maximum of 30 pounds per square inch (PSI). Exceeding this limit can rupture the thin polyethylene tubing or damage the inner seals of the emitters.
If your system is divided into zones, blow out each section sequentially, one zone at a time. Connect the compressor, open the first zone valve, and slowly introduce the air. Allow the air to run until a fine mist or only air is emerging from the open end of that line. Once the first zone is clear, shut off the air compressor before closing the zone valve, and then repeat the process for all subsequent zones. This sequential clearing ensures the system is thoroughly dried without concentrating high pressure.
Final Storage and Preparation for Spring
Once the lines have been cleared of water, attention turns to the removed components and the tubing left in the garden. The disconnected head assembly—including the filters, pressure regulators, backflow preventers, and timers—should be cleaned, drained completely, and stored in a dry, climate-controlled location. This protects the sensitive materials and internal mechanisms from freezing and weather exposure.
For the tubing remaining outdoors, you should loosely reinstall the end caps or flush valves. Leaving them slightly ajar, or vented, allows any minor amounts of trapped moisture to evaporate over the winter months, preventing pressure buildup if an unexpected freeze occurs. You should also cap or cover the open connection point where the head assembly was removed to prevent insects or debris from entering the mainline.