Turning a sprinkler system back on after winter is a short job that protects a large investment. A complete startup runs 30 to 45 minutes, costs nothing in materials, and sits at a beginner skill level. The payoff is avoiding the leaks, frozen fittings, and uneven coverage that appear when a system is pressurized too quickly in spring. Buried infrastructure shares one rule across all its forms: the care it gets at each season change decides how long it serves. A septic system lifespan depends on that same seasonal attention, and sprinkler lines under the lawn behave no differently.
Inspect the System Before You Open the Water
Never pressurize a system you have not looked at since fall. The freeze-thaw cycle cracks plastic bodies, shifts valve boxes, and buries heads under soil. Ten minutes of inspection now prevents a geyser of muddy water later.
Check the Backflow Preventer
The backflow preventer sits above ground, usually near the house or at the highest point of the system. Look for cracks from freezing, a damaged relief valve, or debris packed into the cover. A cracked body means replacement before pressurizing, and that is the one part of the system worth calling a professional for.
Backflow Test Requirements
Many municipalities require a certified backflow test every spring. Book the test before the first irrigation cycle; a failed preventer can contaminate the drinking water supply, and the fine for skipping the test usually exceeds the cost of the test itself.
Inspect Heads and Risers
Walk every zone and look for heads that are broken, tilted, or buried. Grass grows over heads during winter, so clear the soil line before testing. Clogged sprinkler heads and other common irrigation problems are easiest to spot now, while the system is still dry and each head is visible.
Know Your System Layout and Shut-Offs
A sprinkler system has three water controls: the main shut-off at the house, the valve at the backflow preventer, and the electric zone valves buried in the yard. Find all three before you need them, and you can stop a leak in seconds instead of watching it run.
Locate the Main Shut-Off Valve
Most systems have one shut-off at the house and a second at the backflow preventer. If you cannot find the valve box, trace the supply line from the water meter or look for the rectangular green boxes along the foundation.
Map the Zone Valves
The controller opens one zone at a time through electric valves buried in valve boxes around the yard. Older installations follow one of two arrangements: a single main line with branch valves, or a looped layout with valves at each run. The difference between a one pipe and two pipe system explains how water reaches each zone and where air pockets collect during startup, so a quick map of your own layout saves time on the first purge.
Open the Main Valve Slowly and Purge the Lines
The most common spring mistake is opening the main valve all the way at once. Water slams into the empty lines, pushes air through the heads at high speed, and can blow risers out of the ground. Slow is the whole trick.
Purge Air With a Manual Bleed
- Open the main valve a quarter turn and wait 30 seconds.
- Open it halfway and wait another 30 seconds.
- Open it fully once water flows steadily.
- If the zone valves have manual bleed screws, open them to release trapped air.
- Close the bleed screws when water appears, then move to the next valve.
Watch for Spitting and Surges
The first head in each zone should spit air, then settle into a steady spray within a minute. Surges that continue longer usually mean a stuck valve or a partially closed main. The fall routine matters here: a system that was winterized properly, using the same steps that let you winterize your sprinkler system for less than $20 in materials, purges in minutes. Slow or airlocked zones in spring are the first sign that last fall’s shutdown was skipped or rushed.
Test Each Zone and Look for Leaks
With the main open, test every zone before you set the season’s schedule. A zone that fails now will fail all summer, and finding the problem takes longer once the lawn is wet and green.
Run One Zone at a Time
Set the controller to run each zone for three to five minutes and walk the yard while it runs. Watch for heads that do not pop up, heads that spray sideways, and pooling water near valve boxes. Note anything that looks off and fix it before the next zone.
Find Leaks by Watching the Meter
- Turn off all indoor water and note the meter reading.
- Run one zone for ten minutes.
- Re-read the meter and subtract the first reading.
- Compare the result with the expected output for that zone based on its head count and nozzle size.
- A difference beyond the expected output means a leak in that line.
Where the leak hides depends on how the system was built. Underground sprinkler system installation depth and fitting quality decide how easy problems are to find: lines buried at the recommended depth with glued fittings fail far less often than shallow lines assembled with clamps.
Reading the Water Meter
Most meters have a small triangle or dial that spins whenever water flows. If it moves with everything off, you have a leak somewhere in the system, not just in the lawn. That test catches drips that never surface.
| Symptom | Likely Cause | Fix |
|---|---|---|
| No water at any head | Main valve closed or controller off | Open the main valve; check controller power |
| Air spitting past one minute | Air in the line or a stuck zone valve | Purge through the bleed screw; clean the valve |
| Weak spray on one zone | Clogged screen or kinked supply line | Rinse the head screen; check the line |
| Pooling near a valve box | Leaking valve diaphragm or fitting | Rebuild the valve; tighten the fitting |
| One head stays down | Broken riser or worn gear drive | Replace the head |
Service Heads, Nozzles, and Controllers
Testing usually surfaces two or three heads that need work and a controller that forgot its schedule. Deal with both before the first full watering week.
Clean or Replace Nozzles
Remove the cap, rinse the screen, and check the spray pattern. A head that drips or sprays a fine mist instead of a stream has a worn seal or nozzle. Replacing a sprinkler head in an in-ground system takes about ten minutes: unscrew the riser, swap the head, and reset the arc to cover the same area.
Reset the Controller Schedule
Spring watering needs are light. Start with two short cycles per week and adjust as the lawn greens up. Check the clock and the backup battery after a winter without power; a controller that lost its schedule will water at the wrong times until it is reset. Each zone should run long enough to wet the root zone without runoff: on most lawns that is 10 to 15 minutes per zone, three mornings a week in peak summer, less in spring and fall. Program the controller for early morning starts so water soaks in before the sun gets high, and skip scheduled days after rain.
Spring Startup Checklist
- Inspect the backflow preventer for frost cracks
- Clear soil and debris from every head
- Open the main valve slowly and purge each zone
- Run zones one at a time and watch the water meter
- Replace damaged heads, nozzles, and seals
- Reset the controller schedule and backup battery
Watch Drainage and Hardscape During the First Cycle
The first full cycle reveals runoff problems that a quick zone test misses. Water that sheets across walks or pools against the foundation wastes water and damages surfaces over a season.
Inspect Paved Edges and Drainage
Adjust heads so spray stays off walks, driveways, and the house wall. Direct runoff away from the foundation and keep the soil line at the siding clear. Pooling water against hardscape does more than waste water: it can undermine dry stacked interlocking masonry systems that border the lawn, so keep spray and runoff off any un-mortared wall or walk for the whole season.
Log the Startup for Next Fall
Note what you fixed this spring: the valve that stuck, the head you replaced, the zone that ran weak. That log makes next fall’s shutdown faster and next spring’s startup shorter, because the same problems recur season after season. Add the meter reading from your leak test to the log as a baseline, and compare against it each spring before you open the valves.