How To Turn On A Sprinkler System: The Complete Step-by-Step Spring Startup Guide

To safely turn on a sprinkler system, locate the main water shutoff valve, close all manual drain valves and backflow test cocks, and slowly open the main water supply to prevent water hammer and pipe rupture. Once pressurized, activate each zone via the irrigation controller to inspect for leaks, misaligned heads, and system pressure drops. Following this systematic approach protects your backflow preventer and underground PVC piping from high-velocity hydrostatic shock.

Pre-Startup Inspection and Equipment Checklist

Before introducing pressurized water into an irrigation system, you must conduct a thorough physical inspection of all visible components. Activating a system that has sustained winter freeze damage without proper preparation can lead to catastrophic mainline blowouts, flooded basements, and costly landscape erosion.

A successful irrigation de-winterization requires an understanding of your local plumbing codes, specifically regarding backflow prevention. Backflow preventers—such as Pressure Vacuum Breakers (PVBs) or Reduced Pressure Zone (RPZ) assemblies—are mechanical safety devices designed to stop non-potable irrigation water from siphoning back into your clean domestic drinking water supply. Ensuring these assemblies are intact and configured correctly is your first and most critical step.

Essential Gear, Tools, and Materials

• Irrigation Valve Key (Curb Key): Required for deep-buried, underground main shutoff valves.
• Flathead and Phillips Screwdrivers: For adjusting backflow test cocks and adjusting sprinkler head radius screws.
• Slip-Joint Pliers or Channel Locks: To tighten loose fittings or union joints.
• Multimeter: For testing electrical continuity and 24VAC output at the controller if solenoid issues arise.
• Replacement Sprinkler Nozzles and Filters: Standard female-threaded or male-threaded variable arc nozzles (VAN) to replace cracked components.
• Teflon Tape (PTFE): For sealing threaded plastic-to-plastic or plastic-to-metal fittings.

Prerequisite Knowledge & Standards

• Static Pressure Limits: Standard residential irrigation systems operate between 40 and 70 PSI (Pounds per Square Inch). Exceeding 80 PSI without a pressure regulator can damage system valves and nozzles.
• Water Velocity Threshold: Water flow velocity in PVC pipe should remain below 5 feet per second to prevent mechanical failure.
• Local Backflow Testing Regulations: Most municipalities require annual certified testing of RPZ and PVB backflow assemblies upon spring activation.

Estimated Resource Benchmarks

• Estimated Budget: $0 (DIY basic startup) to $150 (if minor nozzle/valve replacements or professional backflow testing is required).
• Estimated Duration: 1.5 to 3 hours depending on the number of zones and the size of the property.

Step-by-Step Sprinkler System De-Winterization and Activation

Follow this structured, sequential procedure to safely pressurize your irrigation system, avoiding the common pitfalls that cause immediate component failures.

Step 1: Locate and Inspect the Main Shutoff Valve and Backflow Assembly

Begin by locating your main irrigation shutoff valve. This is typically situated in a basement, utility room, crawlspace, or outdoors in an underground valve box near the water meter.

Once located, transition to the outdoor backflow preventer assembly. Inspect the brass or plastic body for structural cracks, bulges, or hairline fractures caused by residual ice expansion. Look closely at the test cocks—the small, threaded nipple-like ports on the side of the assembly.

Use a flathead screwdriver to ensure the slot on each of the test cocks is turned perpendicular to the test cock body. This indicates they are in the closed position. If left open, water will spray out of them under high pressure during startup.

Warning: Never attempt to pressurize an irrigation system if you observe visible cracks on the brass casting of your backflow preventer. Pressurizing a damaged unit will result in immediate rupture and localized flooding. Replace the damaged assembly components before proceeding.

Step 2: Set the Backflow Shutoff Valves to the Correct Position

Your backflow assembly features two ball valves: one on the inlet side (bringing water from the house) and one on the outlet side (sending water to the sprinkler valves).

To prepare for pressurization, turn the inlet valve handle perpendicular to the pipe (Closed position) and the outlet valve handle perpendicular to the pipe (Closed position). By starting with both valves closed, you can control the entry of water into the device and isolate the downstream mainline. This isolation allows you to verify that the backflow assembly itself is holding pressure before you expose the rest of your landscape's piping to water.

Step 3: Close All Manual Drain Valves and Bleed Screws

Walk your property to locate any manual drain valves or bleed screws. In colder climates, systems are outfitted with manual drain valves at low points in the mainline to empty water for winter. These must be completely shut (turned clockwise) before turning on the water.

Additionally, locate your zone valve boxes (usually green rectangular boxes flush with the turf). Open the lids and check the solenoid valves. Each valve typically has a small manual bleed screw or lever on top. Ensure these bleed screws are finger-tightened clockwise. If a manual bleed screw is left open, that specific zone will run continuously as soon as the main water line is pressurized.

Step 4: Pressurize the Mainline Slowly (The 1/4-Turn Method)

This is the most critical phase of the activation process. Opening a water valve rapidly introduces high-velocity water into empty PVC pipes. When this water collides with air pockets or closed zone valves, it creates a massive kinetic energy wave known as water hammer (hydrostatic shock). This shock can instantly shatter PVC fittings, crack valve manifolds, and blow sprinkler heads off their risers.

1. Locate your indoor or primary water shutoff valve.
2. Slowly turn the valve handle only one-quarter (1/4) of a turn. You will hear water rushing through the pipe.
3. Wait 1 to 2 minutes. This allows water to slowly fill the supply line up to the backflow preventer, expelling air gently.
4. Once the sound of rushing water stops, open the primary shutoff valve completely.
5. Move outside to the backflow preventer.
6. Slowly open the inlet ball valve (the lower valve) on the backflow preventer by turning the handle parallel to the pipe. You may hear a brief hiss or pop as the internal check valves seat.
7. Slowly open the outlet ball valve (the upper valve) by turning the handle parallel to the pipe. The main line leading to your zone valves is now pressurized.

Pro-Tip: If you hear water running continuously after opening the backflow outlet valve and no zones are actively running, you have an open drain valve, a cracked pipe underground, or a valve diaphragm stuck in the open position. Shut off the main water immediately and inspect the system.

Step 5: Power Up and Program the Irrigation Controller

Navigate to your irrigation controller (timer). If it was unplugged for the winter, plug it into its GFCI outlet.

Replace the backup battery (usually a standard 9V or coin-cell lithium battery) to ensure your programming is preserved during any future power outages.

1. Review the programmed system settings.
2. Set the current date and correct local time.
3. Configure your watering schedule based on seasonal needs. Early spring typically requires significantly less water run-time than mid-summer.
4. Set the zone run times. For testing purposes, set a temporary test program with 2 to 3 minutes per zone.

Step 6: Sequentially Activate and Inspect Each Zone

Do not assume the system is functioning perfectly just because it is pressurized. You must visually inspect every single sprinkler head on your property.

Using the manual run feature on your controller, activate Zone 1.

Walk the zone while it is running and perform the following checks:

• Purge Air: Expect a sputtering mix of air and water for the first 30 to 60 seconds. Wait for a steady, solid stream of water.
• Inspect for Leaks: Look for bubbling water around the base of the sprinkler heads, which indicates a cracked riser or bad wiper seal. Look for pooling water between heads, which indicates a lateral line break.
• Verify Head Rotation and Pitch: Ensure rotor heads are spinning smoothly and covering their designated arcs. If a head fails to rotate, the internal gear drive may be stripped or clogged with debris.
• Adjust Spray Patterns: Use an adjustment tool or flathead screwdriver to set the spray radius, keeping water off your home's siding, windows, driveways, and sidewalks.
• Clean Clogged Nozzles: If a head is misting, barely trickling, or spraying unevenly, unscrew the nozzle, remove the plastic filter screen inside, rinse it thoroughly in clean water, and reinstall it.

Repeat this physical inspection process for Zone 2, Zone 3, and all subsequent zones until the entire system has been verified.

Irrigation System Component and pressure Parameters

To ensure your irrigation system operates within safe mechanical limits, refer to the following technical comparison of common backflow preventer types and baseline system operating parameters.

Common Startup Failures and Field Rectifications

Even when following these instructions closely, physical system anomalies can present themselves during spring startup. Below are the most common field failures, their underlying root causes, and how to fix them.

Scenario 1: Water continuously dumps out of the bottom of the RPZ backflow preventer relief valve

• Root Cause: Debris (such as sand, rust scale, or solder flush) has lodged inside the first check valve seat, preventing it from sealing completely. This creates a pressure differential that forces the relief valve diaphragm open, discharging water to prevent backflow.
• Actionable Fix:
  1. Shut off the main water supply to the backflow device.
  2. Unscrew the top cap or access plate of the backflow assembly using an adjustable wrench.
  3. Carefully extract the first check valve module.
  4. Rinse the rubber seal disc and plastic seat under clean running water to remove all grit.
  5. Reassemble the device, ensuring the O-rings are seated properly, and slowly turn the water back on. If the discharge persists, the internal rubber diaphragm or spring is warped and must be replaced using a manufacturer rebuild kit.

Scenario 2: An entire sprinkler zone fails to turn on electrically via the controller

• Root Cause: A severed common or hot wire in the valve box, or a burned-out solenoid coil on the zone valve.
• Actionable Fix:
  1. Locate the valve box for the non-responsive zone and inspect the wire connections.
  2. Cut away old, corroded wire wire-nuts and strip the copper wires back to expose clean metal. Reconnect using waterproof, silicone-filled wire connectors.
  3. If the wiring is clean, set a digital multimeter to the Ohms ($\Omega$) setting. Place one probe on the zone wire terminal and the other on the common terminal at the controller.
  4. A healthy solenoid should read between 20 to 60 Ohms. If the reading is infinite ($\infty$ or OL) or near zero, the solenoid coil has failed. Unscrew the damaged solenoid counterclockwise from the valve body and thread on a compatible 24VAC replacement solenoid.

Scenario 3: Water leaks from the neck of a sprinkler head when activated

• Root Cause: The internal wiper seal in the sprinkler head cap has degraded, worn down from friction against sand and grit, or cracked during winter freezes.
• Actionable Fix:
  1. Unscrew the entire top cap of the spray head or rotor body while leaving the main body threaded onto the underground pipe riser.
  2. Pull out the spring-loaded riser assembly.
  3. Replace the old cap and wiper seal with a new one of the exact same model, or swap out the entire internal riser assembly.
  4. Screw the cap back down firmly by hand. Do not over-tighten with pliers, as this can strip the plastic threads of the head body.

Frequently Asked Questions

When is the best time of year to turn on my sprinkler system?

The safest time to turn on your sprinkler system is after the threat of the final hard freeze of winter has passed. This is typically when consistent overnight temperatures remain above 32 degrees Fahrenheit (0 degrees Celsius). Activating your system too early leaves the exposed brass backflow preventer and shallow lateral lines highly vulnerable to sudden frost damage.

How do I prevent water hammer when turning on my sprinklers?

To prevent water hammer, you must control the velocity of the incoming water by opening your main water shutoff valve extremely slowly. Utilizing the 1/4-turn method allows the piping network to fill with water gradually, which pushes the air out safely through the sprinkler heads rather than compressing the air and creating high-impact hydraulic shockwaves inside the PVC lines.

Why is water leaking from my backflow preventer during startup?

Water leaking from your backflow preventer during startup is usually caused by either a cracked internal poppet and bonnet assembly from freeze damage, or dirt preventing the internal check valves from sealing. If the water leaks continuously from the plastic canopy top of a PVB, the internal plastic assembly has likely fractured and must be replaced using a standard replacement kit.

What should I do if a single sprinkler zone won't turn on?

If a single zone fails to turn on, try to manual bleed the valve in the valve box by turning the solenoid counterclockwise a quarter-turn. If the zone turns on manually but not from the controller, you have an electrical issue, which is typically a bad wire connection or a failed 24VAC solenoid. If the valve does not open manually, the valve's internal rubber diaphragm is likely torn or stuck shut and requires replacement.

Do I need to clean my sprinkler heads before starting the system?

Yes, it is highly recommended to inspect and clean your sprinkler heads upon startup. Grass clippings, mulch, and soil can collect inside the nozzles over the winter, resulting in clogged streams or preventing the riser from popping up. Unscrew the nozzles on any poorly performing heads, rinse the filter screen located underneath, and flush out any remaining debris before resuming normal operation.

Professional Irrigation Maintenance and Services

Keep your commercial or residential irrigation system operating at peak hydraulic efficiency by scheduling a comprehensive seasonal inspection. Contact our team of certified irrigation professionals today to schedule your annual backflow test and system optimization.