How to Winterize Your Sprinkler System

One hard freeze is all it takes to crack a buried pipe, split a backflow preventer, or shatter a sprinkler valve — and the repair bill can run into the hundreds once you factor in digging. Winterizing your irrigation system before the first deep frost is a couple of hours of work that protects thousands of dollars of buried plumbing. Here’s how to do it right.

What you’ll need

• Air compressor — for the blow-out method; you want real airflow (CFM), not just pressure — a small pancake unit won’t cut it
• Quick-connect blow-out adapter — the fitting that mates your compressor hose to the system’s blow-out port
• Adjustable wrench — for the backflow test cocks and isolation valves
• Screwdrivers — for manual drain valves and controller access
• Pliers — for stubborn drain caps and bleeder screws
• Safety glasses — non-negotiable if you’re using compressed air
• Work gloves — valve boxes are cold, wet, and full of grit this time of year
• Foam faucet covers & pipe wrap — to insulate the exposed backflow and any above-ground pipe
• Insulation — foam sleeves or wrap for the riser and valve body
• Replacement sprinkler parts — keep a couple of heads and nozzles on hand in case one lifts during the blow-out

Step 1: Know your system and shut off the water

Find the main shut-off for the irrigation system. It’s usually a dedicated valve where the sprinkler line branches off your home’s supply — in the basement, a crawlspace, or an underground shut-off valve near the water meter. Close it fully. If your system has a separate isolation valve at the backflow preventer, close that too.

Common mistake: turning off the controller and calling it done. The timer stopping the schedule does nothing to remove water from the pipes. The water in the ground is what freezes and cracks — you have to physically get it out.

Step 2: Shut down the controller

Set the controller to “Rain” or “Off” so it doesn’t fire the valves all winter. Most modern controllers (Rain Bird, Hunter, Orbit) keep your programmed schedule in memory even when set to off, so you won’t have to reprogram in spring. If yours is battery-backed, pull the battery so a dead cell doesn’t corrode over the winter.

Step 3: Choose your drain method

There are three ways to clear the water. Which one you use depends on how your system was built — check the table below. If you have any doubt about which type you have, the blow-out method clears everything, but it’s also the one that can damage components if done wrong.

Step 4: Drain the lines

For a manual-drain system, open each drain valve at the low points and let the water run out, then open the boiler-drain or bleeder on the backflow to clear water trapped between the shut-off and the valves. For an automatic-drain system, turn on one zone at the controller briefly to relieve pressure, and the drains do the rest. Open the test cocks on the backflow preventer with your wrench to drain the assembly itself — that brass device is the single most freeze-prone and expensive-to-replace part of the whole system.

Step 5: Blow out the zones (if needed)

If you’re using compressed air, this is where care matters. Connect your compressor to the blow-out port with a quick-connect fitting, and put on your safety glasses first. With the compressor OFF, open one zone at the controller. Then slowly introduce air — and keep the pressure LOW: 50 PSI for rigid PVC, no more than 40 PSI for flexible poly pipe. Run each zone only until the heads spit mostly mist, then move to the next zone. Never run air through a zone with no head open — that’s how you blow a fitting apart underground.

Pro tip: pressure is not the enemy — heat is. Running a zone dry for more than 60 seconds lets the fast-moving air overheat and warp the plastic gears inside your rotor heads. Short bursts, one zone at a time, and let the compressor catch up between zones. If you don’t own a compressor with enough CFM, this is the step worth handing to a pro — a botched blow-out costs more than the service call.

Step 6: Insulate the exposed parts

Anything above ground can still freeze even after the lines are empty, because trapped droplets and condensation collect at low points. Wrap the backflow preventer and its exposed piping with foam insulation, and slip insulated covers over the riser and any hose bibs feeding the system. Leave the test cocks cracked slightly open so any water that does collect has somewhere to expand. Coil and store your garden hoses indoors while you’re at it — a hose left connected traps water against the spigot and is a classic cause of a burst pipe just inside the wall.

Step 7: Do a final walk-through

Confirm the main irrigation shut-off is closed, the controller is off, every drain and test cock has been addressed, and the backflow is wrapped. Snap a quick photo of your valve locations and settings on your phone — spring-you will be grateful. Note anything that needs replacing now, like a cracked head or a leaky zone valve, so you can pick up the part before the spring rush.

Frequently asked questions

Winterizing is one of those jobs that’s cheap insurance against an expensive spring. If you’re unsure which drain method your system uses, or you’d rather have a hand with the blow-out, your local independent hardware store can point you to the right adapter or the right person for the job — or you can ask us here. Do it once, do it right, and forget about it until the tulips come up.