The process of dewinterizing an irrigation system involves the careful reintroduction of water into pipes that have been drained and dormant, often for several months. This procedure is essentially a controlled start-up, designed to bring the system back online without causing mechanical failure. The primary objective is to prevent damage from water hammer or sudden pressure surges, which can easily rupture plastic pipes and fittings that may have become brittle from cold temperatures. A slow, methodical approach ensures that air is purged gradually and that the system components are tested under increasing pressure before full operational flow is achieved.
Pre-Activation Safety Checks
Before opening the main water supply, a thorough physical inspection of the entire system must be completed to ensure structural integrity. Set the irrigation controller to the “Off” or “Rain” position to prevent automatic valve activation during pressurization, which could exacerbate water hammer effects. Walk the property to check sprinkler heads for obvious physical damage, such as cracks or misalignment caused by ground movement or traffic during the winter.
Verify that all manual drain valves and flush caps have been returned to the fully closed position after the winterization process. If the system includes a backflow prevention device (typically a brass assembly above ground), examine it carefully for cracks or loose fittings before restoring its operational orientation. Visible damage requires immediate professional attention, as this device prevents contaminated irrigation water from mixing with the potable household supply. Completing these checks minimizes the risk of immediate, uncontrolled leaks when water is introduced.
Controlled Pressurization of the Main Line
The most delicate phase of the dewinterizing process is the controlled reintroduction of water pressure to the primary mainline, which must be done gradually to manage hydraulic forces. Water hammer is a pressure shockwave created when moving fluid is forced to stop or change direction abruptly, generating pressure spikes much higher than the system’s static pressure. Since the pipes are filled with air, opening the water source too quickly allows water to rush in at high velocity, causing a severe shock when it reaches a closed valve or the end of a segment.
To mitigate this, open the main isolation valve that connects the irrigation system to the water source only a quarter to a third of the way. This slow opening allows water to flow gently into the empty pipes, gradually compressing trapped air and pushing it toward the sprinkler heads and open ports. Maintain this partial flow for several minutes until the sound of air escaping from the system subsides and the pipes are partially filled and stabilized.
Once the initial rush of air has ceased, open the main isolation valve halfway, further increasing pressure and ensuring all mainline segments are filling consistently. Allow this intermediate step to stabilize for a few additional minutes without any noticeable surge or noise. Finally, open the main valve completely, allowing the system to operate at full static pressure, provided a careful inspection confirms no leaks have appeared at the backflow preventer or mainline connections.
Zone Testing and Head Calibration
With the mainline fully pressurized, the focus shifts to testing each irrigation zone sequentially using the system’s controller. Manually activate each zone one at a time, allowing a few minutes of observation to assess the performance of the sprinkler heads and the integrity of the lateral lines. Walk the zones while they are active to identify immediate issues, such as geysering water indicating a broken lateral pipe or a loose head seal.
During this operational check, pay attention to the spray patterns and arc coverage of individual heads. Nozzles may require adjustment to ensure water is delivered uniformly across the intended area, avoiding sidewalks, driveways, or structures. Rotator heads sometimes need slight calibration to refine the degree of rotation and throw distance, typically adjusted with a small flat-head screwdriver or specialized tool. Check for leaks at the base of the sprinkler head, as weeping can indicate a faulty seal or a cracked riser connection.
Fixing Common Start-Up Problems
Several common issues may surface immediately after the initial pressure test and zone activation, often related to debris or minor winter damage. Low water pressure across an entire zone frequently indicates a significant underground leak in the lateral piping. Investigate unusually saturated spots of soil or overly green patches of grass to pinpoint the exact location of a pipe break for repair.
Sprinkler heads that fail to pop up fully or spray erratically are typically caused by dirt, sand, or mineral deposits clogging the internal filter or nozzle. Cleaning a clogged head involves lifting the pop-up riser, removing the nozzle, and flushing the filter screen. If a valve sticks open, causing water to run continuously even when the controller is off, the issue often lies with a damaged diaphragm seal or a stuck solenoid within the valve body. While tightening the packing nut may offer a simple fix, internal components sometimes require full replacement to restore proper sealing and operation.