Winterizing your sprinkler system is crucial for preventing costly damage from freezing pipes. Blowing out the lines with an air compressor is an effective way to remove water, but using the wrong air pressure can be just as damaging. This guide will help you understand the right approach to keep your system safe and sound.
Quick plan (TL;DR)
- Shut off the main water supply to your irrigation system.
- Drain residual water from the backflow preventer.
- Connect your air compressor to the designated blow-out port.
- Set your compressor's pressure regulator appropriately for your system.
- Open the furthest sprinkler zone valve first.
- Introduce air slowly, allowing water to exit, then move to the next zone.
- Ensure all zones are clear before disconnecting.
- Recheck all valves are closed for winter.
Before you start
Blowing out your sprinkler system yourself can save you money, but it requires careful attention to detail and safety. The primary risk is using excessive air pressure, which can damage sprinkler heads, valves, and even the main lines. It's a moderately difficult DIY task; if you're uncomfortable working with pressurized systems, consider hiring a professional. Confirm your system has a dedicated blow-out port; older systems might not, complicating the process.
Tools & materials
Tools
- Air compressor (minimum 5-10 CFM at 90 PSI, 20-30 gallon tank recommended for larger systems)
- Air hose with appropriate quick-connect fittings
- Sprinkler blow-out adapter (threaded for your system's port, typically 1/4" or 1/2" NPT)
- Adjustable wrench or pipe wrench
- Safety glasses
- Work gloves
- Tire pressure gauge (to double-check compressor gauge)
Materials
- Thread sealant tape (PTFE/Teflon tape) or pipe dope
- Optional: Old towels for spills
Time, cost, and difficulty
- Time: 1-3 hours, depending on system size and familiarity. A small residential system might be 1 hour, while a large, multi-zone system could take longer.
- Cost:
- If you own the tools: $5-$15 for an adapter and sealant.
- If you need to rent/buy tools: Air compressor rental costs $50-$100 per day. Purchasing a suitable compressor can range from $200-$500+.
- Difficulty: Moderate. Requires mechanical aptitude, understanding of air pressure, and patience.
Step-by-step instructions
- Shut Off Main Water Supply: Locate the main water shut-off valve for your irrigation system (usually near your house's main water line or backflow preventer). Turn it completely off.
- Drain the Backflow Preventer: If your system has a backflow preventer, follow its manufacturer's instructions to drain it. This typically involves opening test cocks or drain valves. Leave these open for now.
- Locate and Prepare the Blow-Out Port: Find the dedicated blow-out port on your system. It's usually a small pipe with a cap, often located near the backflow preventer or main shut-off. Remove the cap.
- Connect the Adapter: Apply thread sealant tape or pipe dope to the threads of your blow-out adapter. Screw the adapter firmly into the blow-out port. Hand-tighten, then give it a quarter-turn with a wrench.
- Connect Air Hose to Adapter: Attach your air hose from the compressor to the adapter. Ensure a secure connection.
- Set Compressor Pressure: This is critical. Rule of thumb: Never exceed 50 PSI for any PVC irrigation system, and ideally stay between 20-40 PSI for most residential systems. For older or more fragile systems, start even lower (around 20-30 PSI). Check your specific sprinkler head manufacturer's recommendations; rotor heads can often handle higher pressure than spray heads. Use the pressure regulator on your compressor to set the output pressure before connecting it.
- Open the Furthest Zone Valve: Start with the sprinkler zone furthest from your compressor. Manually open only one zone valve completely. Keep all other zone valves closed.
- Introduce Air Slowly: Gradually open the air valve on your compressor or the quick-connect fitting to allow air into the system. You'll see water spitting out of the open zone's sprinkler heads. Allow the air to push the water out until only a mist or air is visible. Do not run the compressor continuously for more than a minute or two per zone without giving it a break to cool down.
- Cycle and Repeat: Once the first zone is clear, close its manual valve. Then, open the next furthest zone valve and repeat the air-blowing process. Continue this methodically, moving from the furthest zone to the closest, until all zones have been cleared of water.
- Final Checks and Disconnection: Once all zones are cleared, ensure all zone valves are closed. Close the main shut-off valve on the backflow preventer (if you opened it to drain). Disconnect the air hose and adapter. Replace the cap on the blow-out port.
- Close Backflow Preventer Test Cocks: Close any test cocks or drain valves you opened on the backflow preventer.
Common mistakes to avoid
- Too much pressure: The most common and damaging mistake. Can rupture pipes and sprinkler heads. Always regulate pressure.
- Opening all zones at once: Air will take the path of least resistance, leaving some lines undrained. Clear one zone at a time.
- Blowing dry too long: Once only mist is coming out, the line is mostly clear. Excessively long blowing can generate friction heat, potentially damaging PVC.
- Not fully draining the backflow preventer: This component is particularly vulnerable to freezing.
- Forgetting to shut off the main water: You'll just be blowing water, not clearing lines.
- Forgetting to open the furthest zone first: Starting closer to the compressor can trap water further down the line.
Troubleshooting
| Symptom | Likely Cause | Fix |
|---|---|---|
| No water/air coming out | Main water supply still on, or a closed valve. | Ensure main water is off and the specific zone valve is fully open. |
| Low pressure at sprinkler head | Compressor output too low, or leak. | Increase compressor PSI (staying within safe limits). Check connections for leaks. |
| Water still pooling | Inadequate blowing time or trapped water. | Continue blowing for 30-60 seconds after water subsides. Check for low spots in the line. |
| Compressor keeps running | Air leak in system or compressor too small. | Check all connections for leaks. For larger systems, a compressor with higher CFM may be needed. |
| Sprinkler heads don't pop up | Low pressure, or clogged heads. | Increase pressure slightly (within safe limits). Manually pull up heads and check for debris. |
Safety notes
- Eye Protection: Always wear ANSI-approved safety glasses or goggles. Compressed air can propel debris at high speeds.
- Hearing Protection: Air compressors can be loud. Consider earplugs or earmuffs, especially for prolonged use.
- Pressure Hazards: Never point an air hose or sprinkler head at yourself or others while under pressure. Escaping air can cause serious injury.
- Read Manuals: Always consult your air compressor and sprinkler system manufacturer's instructions for specific safety warnings and operating procedures.
- Electrical Safety: Ensure your compressor is plugged into a properly grounded outlet. Do not use extension cords that are undersized or damaged.
- Component Integrity: Inspect all hoses, fittings, and pipes for signs of damage before starting. Do not use damaged equipment.
- Children and Pets: Keep children and pets away from the work area during the entire process.
FAQ
Q: Can I use my garage air compressor? A: Yes, provided it can produce at least 20-40 PSI consistently and has a sufficient tank size (20-30 gallons recommended) to avoid constant cycling. A higher CFM (Cubic Feet per Minute) rating helps.
Q: What happens if I use too much pressure? A: Excessive pressure can rupture PVC pipes, break sprinkler heads, damage internal valve components, and even cause dangerous project failure. Always regulate your pressure.
Q: Do I need to drain the backflow preventer separately? A: Yes, absolutely. Backflow preventers are highly susceptible to freeze damage due to their internal components. Always follow the manufacturer's draining instructions.
Q: How do I know if all the water is out? A: When only a fine mist or clear air comes out of the sprinkler heads, the line is mostly clear. You might not get every single drop, but the minimal remaining water won't cause freeze damage.
Q: Should I worry about trapped water in low spots? A: Modern sprinkler systems are usually designed with adequate drainage or self-draining heads. If you have known significant low spots, you may need to run air through those zones slightly longer, but generally, the main concern is the horizontal pipe runs and heads.
Q: Can I use my leaf blower instead of an air compressor? A: No. Leaf blowers move a high volume of air at very low pressure, which is insufficient to push water out of irrigation lines effectively. An air compressor provides the necessary sustained pressure.
Sources & claims handling
Always refer to the specific instructions provided by your irrigation system and air compressor manufacturers. Local building codes may also have requirements for backflow preventer winterization. Reputable organizations like the Irrigation Association, Plumbing-Heating-Cooling Contractors National Association (PHCC), and Occupational Safety and Health Administration (OSHA) provide general guidelines. Consult a licensed irrigation professional if you are unsure about any steps or your system's specific needs.
Properly winterizing your sprinkler system protects your investment and prevents frustrating, costly repairs. By understanding and applying the correct air pressure and following these safe, step-by-step instructions, you can confidently prepare your irrigation system for the cold season. Remember, safety first – wear your protective gear and work patiently.