How to Winterize Irrigation Systems and Outdoor Faucets

Winterizing irrigation and outdoor faucets means draining or blowing residual water out of every line, valve, and backflow device before the first hard freeze, because water expands roughly 9% as it turns to ice and will crack whatever container holds it — PVC pipe, brass fittings, or a backflow preventer. Do it before your first freeze warning, not after.

What's the actual process for winterizing a sprinkler system?

1. Shut off the water supply to the irrigation system at the main valve.
2. Shut off the automatic controller or set it to rain mode/off so it doesn't try to run a dry system.
3. Open manual drain valves at the low points of the system, if your setup has them, and let gravity drain the lines.
4. For systems without manual drains, use a compressed-air blowout: attach an air compressor to the mainline, then open each zone in turn and blow residual water out through the sprinkler heads.
5. Insulate the backflow preventer and any exposed above-ground piping with foam pipe insulation or an insulated cover.
6. Leave drain valves and controller off until you reactivate the system in spring.

Can I blow out my own sprinkler lines, or do I need a pro?

You can do it yourself with a compressor rated for at least 80-100 CFM for larger multi-zone residential systems (a typical home shop compressor often isn't big enough — check its CFM rating, not just tank size or PSI). Keep air pressure under about 50 PSI for PVC systems and under 80 PSI for polyethylene to avoid blowing out fittings or cracking heads. If you don't own or want to rent a large compressor, hiring an irrigation contractor runs $50-150 for a typical residential system depending on zone count.

How do you winterize outdoor hose bibs?

Disconnect every hose — a hose left attached traps water in the bib and defeats even a frost-proof faucet. If you have interior shutoff valves for exterior spigots (common in colder climates), close them and open the outside tap to drain and relieve pressure, then leave it open slightly through winter. If you don't have an interior shutoff, a foam or hard-shell insulated faucet cover ($3-15) adds meaningful protection but isn't a substitute for draining if you have a standard (non-frost-proof) bib.

What does it cost when winterizing gets skipped?

• A cracked backflow preventer typically runs $150-400 to replace, plus labor.
• A split zone valve or lateral line repair runs $100-350 depending on accessibility.
• A burst hose bib that leaks into a wall can cause hidden water damage costing $500-3,000+ to remediate.
• Full system repiping after severe freeze damage can run into the thousands, far above the $50-150 a blowout would have cost.

What happens if you wait too long to winterize?

Waiting past the first hard freeze means water already sitting in the mainline, valves, and backflow preventer has a chance to freeze before you drain it, which is exactly the scenario that cracks PVC and brass fittings. Even one missed cold night in the 20s can be enough if the system wasn't drained — the damage often isn't visible until spring startup, when a cracked valve or split lateral line shows up as a geyser or a soggy patch of lawn the moment water pressure returns. If you missed the window and a hard freeze already hit, check the backflow preventer and any exposed piping for cracks before restarting the system, rather than assuming it survived.

How do you reactivate irrigation safely in spring?

1. Wait until nighttime lows are reliably above freezing for at least a week before turning the main water supply back on.
2. Open the main valve slowly rather than all at once, which lets air escape gradually instead of causing a pressure surge (water hammer) that can damage fittings weakened over winter.
3. Run each zone individually and watch for wet spots, weak spray, or heads that don't pop up — signs of a leak or debris that settled into a line over winter.
4. Check the backflow preventer for cracks before pressurizing it, since a damaged one can fail suddenly under pressure rather than gradually.
5. Reset the controller's schedule for spring conditions rather than leaving it on the setting from the previous fall.