Winterizing a sprinkler system is a mandatory seasonal task for homeowners in cold climates to protect underground pipes and components from freeze damage. When water freezes, it expands by approximately nine percent, creating immense pressure that can easily split pipes, valves, and fittings, leading to expensive repairs. While the “blowout” method using compressed air is common, many systems, particularly those in milder climates or designed with specific drainage features, can be safely winterized without a compressor. This approach relies primarily on gravity and manual procedures to remove standing water from the irrigation network, preparing the system for months of freezing temperatures.
Essential System Shutdown and Prep
The initial steps focus on isolating the irrigation system completely from its water source and power supply. You must first locate and turn off the main water shut-off valve, often found in a basement, crawl space, or an underground box near the water meter. This action prevents new water from entering the lines while draining takes place. Next, the automatic irrigation controller must be deactivated to ensure it does not attempt to cycle on while the water is off, which could damage the system’s electric solenoids.
If your controller has a specific “rain mode” or “off” setting, use it to shut down the unit for the season. Immediately after shutting off the main water supply, relieve any residual pressure trapped in the pipes. This is often achieved by briefly running one of the sprinkler zones manually or opening a drain valve on the main line. Relieving this pressure is a necessary step before proceeding to the deeper draining procedures.
Step-by-Step Manual Drain Procedure
The non-blowout method depends entirely on gravity, requiring the system to be equipped with manual or automatic drain valves at specific low points. For systems with manual drain valves, locate these caps or valves, which are usually situated at the end of each zone line or at the lowest elevation points of the underground piping. The goal is to open these valves sequentially and allow the water to flow out naturally.
Start by opening the drain valve closest to the main water shut-off, if one exists, to clear the main supply line. Then, open the drain valves for each zone, starting from the highest point and working progressively towards the lowest elevation point. This sequence uses gravity to pull the water through the pipes and out of the system. Once the water flow has ceased, leave the manual drain valves slightly open—or at a 45-degree angle—over the winter to allow any residual moisture to escape and prevent pressure buildup from minor freezing.
Systems featuring automatic drain valves simplify this process, as these specialized valves are designed to open automatically when the water pressure in the line drops below a certain threshold, typically around 10 pounds per square inch. However, even with automatic valves, manually opening the solenoid on the zone valves can help ensure every drop of water is expelled, as residual water can still collect in the valve body. Any standing water left behind will expand upon freezing and cause pipe damage.
Insulating and Securing Exposed Components
Even after underground pipes are drained, above-ground components remain vulnerable to freezing temperatures because they are exposed to ambient cold and wind chill. The backflow preventer (BFP), designed to stop water contamination, is particularly susceptible to damage and is often one of the most expensive parts to replace. To prepare the BFP, drain the water it holds by opening the test cocks and the ball valves, often turning them to a 45-degree position to ensure the device is completely empty.
Once drained, the BFP and all other exposed pipes, such as the main water line leading into the ground, must be protected with insulation. Specialized insulating bags, foam pipe wrap, or insulation tape can be used to cover the brass or plastic components, creating a thermal barrier. When insulating the BFP, avoid blocking any air vents or drain outlets, as these need to remain functional. Finally, above-ground solenoid valves and manifold assemblies should also be covered or wrapped, as they often retain small pockets of water that can freeze and crack the plastic housing.
When Manual Draining Is Not Enough
While the manual drain method is effective in milder climates, it has significant limitations that homeowners must recognize to prevent freeze damage. In regions experiencing prolonged, deep freezes (USDA Hardiness Zones 6 and colder), the manual method is often insufficient because the frost penetrates deep into the ground, freezing water slightly below the surface. In these environments, the professional air blowout procedure is recommended for maximum protection.
System design can also compromise the effectiveness of gravity draining, especially in systems with complex, undulating terrain or pipes that have sagged over time, creating low-lying “saddles”. These dips inevitably trap water that cannot be removed by gravity alone, which will freeze and rupture the pipe. If a homeowner attempts a manual drain and notices water continues to flow excessively, or if they have a highly complex system, it signals that manual draining is not achieving a complete purge. In such cases, the safest course of action is to hire a professional with a high-volume air compressor to prevent potential damage.