How Do I Winterize My Sprinkler System in Oklahoma?
In-ground sprinkler systems are one of the most overlooked freeze risks in an Oklahoma yard. Here's when to winterize, why the backflow preventer is the part that cracks first, and what you can safely do yourself before the first hard freeze.
Sprinkler systems are easy to forget once the growing season winds down — you turn them off, the grass goes dormant, and the controller sits quietly in the garage until spring. But an in-ground irrigation system is still plumbing: pressurized pipes, valves, and a backflow assembly full of water. When that water freezes and expands, it cracks whatever’s holding it, and the damage usually doesn’t show up until you turn the system back on in April and find a geyser where a spray head used to be.
A common call we get around the Oklahoma City metro every fall is from a homeowner who shut the sprinklers off for the season, assumed “off” meant “safe,” and never actually got the water out. Then a hard November freeze split the backflow preventer sitting above ground by the side of the house. It’s one of the most preventable plumbing repairs there is — and the window to prevent it is now.
Why an Oklahoma freeze is hard on a sprinkler system
Water expands when it freezes. Inside a rigid pipe, valve body, or backflow assembly, that expansion has nowhere to go, so it forces the material apart — cracking PVC, splitting brass, and popping seals. It doesn’t take a week-long ice storm, either. A single hard overnight freeze on a line that’s still full of water is enough.
Oklahoma makes this trickier than a steadier northern climate because our fall runs warm and unpredictable. We’ll get 80-degree afternoons well into October, then a sudden cold front drops us below freezing overnight. That whiplash lulls people into leaving the system charged with water far longer than they should — right up until the freeze that finally does the damage.
The part most likely to crack: your backflow preventer
If you protect one component, make it the backflow preventer. This is the brass (or occasionally plastic) assembly, usually mounted above ground near where the irrigation line leaves the house, that keeps sprinkler water — which can pick up fertilizer, pesticides, and standing water from the yard — from being siphoned back into your drinking water. It’s required by code, it’s testable, and because it sits exposed to the air, it’s the first thing to freeze.
A cracked backflow assembly is the most expensive winter sprinkler failure we see, precisely because it’s a plumbing device tied into your potable water supply, not just an irrigation part. Draining it and shielding it from the cold is the highest-value thing you can do before winter.
When to winterize in the OKC metro
You don’t have to do this the first cool morning of September. The target is simple: get it done before the first hard freeze, which around here typically arrives in late October or November. Early-to-mid fall is comfortable, dry-weather timing to take care of it without pressure.
What you don’t want is to be scrambling the evening a freeze warning pops up. Plan it as a fall chore alongside your other pre-winter tasks rather than a reaction to the forecast.
How the system actually gets drained
Getting the water out is the whole job, and there are three common methods:
- Manual drain. If your system has manual drain valves at the low points, you shut off the water supply and open them to let the lines gravity-drain. Straightforward, but only works if the system was installed with these valves and they still function.
- Automatic drain. Some systems have valves that drain on their own once pressure drops below a threshold. You still need to relieve pressure and clear water trapped between the shutoff and the valves.
- Blow-out. Compressed air is pushed through the lines to force the water out through the heads. In our climate this is the most reliable method and the one most local systems use, because gravity draining alone rarely clears every line completely.
Whatever the method, the sequence is the same idea: shut off the water supply to the irrigation system, relieve the pressure, get the water out of the pipes and valves, and protect the backflow preventer with insulation or an insulated cover (leaving its drains cracked open so any trapped water can escape). Don’t forget to shut off the controller or set it to “rain/off” mode so it isn’t trying to run dry zones all winter.
What you can do yourself, and where to bring in help
The homeowner-friendly parts: locating and closing the irrigation shutoff valve, opening manual drains if you have them, shutting down the controller, and wrapping the backflow assembly for insulation. Those are worth doing yourself.
The blow-out is where people get into trouble. A proper blow-out uses high air volume at low, carefully controlled pressure — the opposite of the instinct to crank up a small compressor’s PSI to make up for its lack of volume. Too much pressure cracks fittings and blows out spray heads and seals, which means you’ve traded a $0 winterizing job for a spring repair bill. And if your backflow preventer is due for its code-required test, or you’re not confident the assembly is fully drained, that’s plumbing work worth handing off. Our plumbing team can handle the backflow side — shutoff, draining, testing, and repair — so the part most likely to fail goes into winter protected.
The bottom line
Winterizing a sprinkler system comes down to one goal: no standing water left in the pipes, valves, or backflow preventer when the first hard freeze hits. Get the water out, shield the backflow assembly, shut down the controller, and do it before the freeze arrives rather than after the forecast turns. The buried lines matter, but it’s the exposed backflow preventer that cracks first and costs the most — so that’s the piece to protect.
If you’d rather not gamble on a shop compressor, or your backflow preventer needs draining or its annual test before the cold sets in, Triple Play Home Services helps homeowners across Edmond, Oklahoma City, and the surrounding metro — with flat-rate pricing you approve up front before any work begins. Call (405) 500-5333 and we’ll make sure your system is ready for winter.
Frequently asked questions
- When should I winterize my sprinkler system in Oklahoma?
- Aim to have it done before the first hard freeze, which around the OKC metro usually lands in late October or November. You don't need to rush it in early fall, but don't leave it until a freeze is already in the forecast — the goal is to get the water out of the pipes and above-ground parts before they're ever asked to survive a night below freezing.
- Will my sprinkler pipes really freeze if they're buried underground?
- The buried lateral lines are usually shallow enough that a hard Oklahoma freeze can reach them, but the bigger risk is everything that sits above ground or just below the surface: the backflow preventer, the shutoff valves, and any exposed piping. Those freeze first and crack easily, and a cracked backflow assembly is the single most common — and most expensive — winter sprinkler repair we see.
- Can I blow out my own sprinkler lines with a shop air compressor?
- Usually not safely. A typical home or shop compressor doesn't move enough air volume (CFM) to clear the lines, so people compensate with high pressure (PSI) — and too much PSI cracks fittings, blows seals, and can rupture spray heads. A proper blow-out uses high volume at low, controlled pressure. If you're not sure your equipment can do that, it's cheaper to have it done than to replace damaged heads and valves in spring.