· by Michael Blair, Nashville's Irrigation
Most people think of spring start-up as flipping the controller back to Auto. It is really a short inspection done in a fixed order, because a system that sat empty since fall comes back to life with whatever the winter did to it still hidden underground. Here is the order our crews follow on a spring start-up and winterization visit, why each step comes where it does, and why the annual backflow test in Middle Tennessee is tied to the turn-on rather than the shutdown. If you are in Williamson County, the same steps apply on our Brentwood irrigation page; only the water utility’s paperwork differs.
Wait for the ground, not the calendar
The first decision is when. Rain Bird’s spring start-up guide for homeowners says the soil should be completely free of frost at least 12 inches down before the system is started, because water pushed into lines in frozen ground can burst pipes. A warm week in early March does not settle that question here. Middle Tennessee sits in the transition zone, and a hard freeze in late March or even April is a normal part of our spring, not a freak event.
Our clay adds a second reason for patience. Heavy soil holds winter rain and stays cold and wet well after the air warms, and a lawn sitting in that does not need irrigation yet. Turning the water on early mostly exposes a full system to the next frost. We would rather start a week late than come back to repair a cracked manifold or a split backflow body.
Look before any water moves
Before the main valve is touched, the system gets a dry inspection. Rain Bird’s guide starts at the backflow preventer and the valves: look for freeze damage, make sure the drain plug is tight, and confirm the valves are closed. That matters most on systems that were drained in the fall, because the winterizing process leaves test cocks and drains open on purpose, and any one left open in spring turns into a fountain the moment pressure arrives.
Then the heads. Over a winter, grass, sand and rock work down around sprays and rotors, and a mower or a cold snap can crack a cap. Rain Bird recommends clearing debris away from each head and replacing anything cracked or chipped before the season starts. Last comes the controller. A power outage over the winter can leave it with the wrong date and time, so we check that first and set it to manual so each station can be run on its own.
- Backflow preventer and valve boxes: freeze cracks, tight drain plug, valves closed
- Heads: debris cleared from around each spray and rotor, cracked parts replaced
- Controller: date and time correct, set to manual for testing
Fill slowly, then walk every zone
The single step that does the most damage when rushed is opening the main valve. Rain Bird warns that opening it too fast causes water hammer, a pressure surge that can damage pipes and valves. An empty line fills with a rush of air ahead of the water, and when that water slams into a closed valve the shock travels back through every fitting. We open the supply a little at a time and let the lines fill and purge before going further.
With the system full, each station is run by hand and walked end to end. Rain Bird lists what to watch for: heads that do not pop up or spray, gaps in coverage, water pooling around a head or over a pipe, and heads that mist instead of throwing distinct streams. Misting can mean pressure that is too high or too low, a blocked nozzle, or something larger, and the guide suggests a pressure gauge with a target range of 45 to 75 PSI. Pooling over a line is often where the winter did its work, a crack that only opens once the pipe is under pressure. Anything we find goes onto a sprinkler repair list before the schedule is set.
Only after every zone runs clean does the controller get its spring program. Rain Bird’s guide says to set it for local watering rules, your soil type and spring temperatures, which in practice means shorter, less frequent cycles in April than the system will need in July. A smart controller can make that adjustment through the season on its own, but the starting program still needs a person to set it.
The backflow test belongs to start-up
This is the part homeowners most often miss. Every irrigation system on public water has a backflow preventer, the assembly near the meter that keeps lawn water, and whatever fertilizer or weed control is in the soil around the heads, from being drawn back into the drinking water supply. Metro Nashville Codes’ backflow page states that pools, irrigation and sprinkler systems require backflow preventers, and that the device has to pass an initial inspection and an annual inspection after that. The page also says the assembly goes outside, directly behind and as close to the water meter as possible, and that a failed device is reinspected after the plumber contacts Metro Water Services.
The timing is the detail that changes how a start-up is scheduled. The Consolidated Utility District of Rutherford County’s cross-connection policy for irrigation systems explains that the State of Tennessee treats lawn irrigation as a high-risk, health-hazard cross connection, and quotes the state Division of Water Supply rule that irrigation backflow devices be tested after installation and during start-up each year. CUD requires the test every 365 days by a tester holding a Certificate of Competency it approves, requires a reduced pressure zone assembly on irrigation, and does not accept a test done before the fall shutdown. That policy covers CUD customers; other utilities in Middle Tennessee set their own deadlines and keep their own lists of approved testers, so the place to confirm yours is your water bill’s utility.
The reasoning is simple once you see it: a device tested in October then sits through a winter of freezes before it protects anyone, and the spring turn-on is the first time it is back under pressure. Doing the test as part of the start-up means it is checked in the condition it will actually work in all season. Our page on backflow testing and certification and the post on backflow preventers and annual testing cover what the test involves and what a failure means.
If your system has not been turned on yet this year, or you are not sure whether last year’s test was done at the right time, ask us for a start-up visit and tell us which utility serves the house. We will plan the turn-on and the test together.
Sources
- Rain Bird, Is Your Sprinkler System Ready for Spring? — Frost-free 12 inches deep; inspect backflow and valves; open the main valve slowly to avoid water hammer; test each station; 45 to 75 PSI; reprogram for spring
- Metro Nashville Codes, Backflow — Irrigation and sprinkler systems require backflow preventers, with an initial and an annual inspection; installed behind the water meter
- Consolidated Utility District of Rutherford County, Cross Connections at Irrigation Systems: CUD Policy — Irrigation is a high-risk cross connection in Tennessee; backflow tested after installation and during start-up each year; tests before shutdown not accepted