A single hard freeze can turn a small amount of trapped water into a cracked pipe, damaged valve, or broken backflow preventer. Knowing how to winterize sprinkler system lines before cold weather arrives protects the irrigation system you rely on to keep your lawn and landscaping healthy all summer.
For many homeowners, winterization is not just a matter of turning off the controller. Water can remain in underground pipes, sprinkler heads, valves, and above-ground components long after the schedule stops. The goal is to shut off the water supply and remove as much remaining water as possible before temperatures stay below freezing.
Know When Your System Needs Winterizing
If you live in an area where the ground freezes or temperatures regularly fall below 32°F, your sprinkler system should be winterized each fall. Do not wait for the first deep freeze if you can help it. Once temperatures are consistently cool and your lawn no longer needs regular irrigation, it is time to plan the shutdown.
The right timing depends on your local weather and the type of irrigation system you have. A brief overnight frost may not damage buried pipes, especially if the ground is still warm. Several hours of freezing temperatures, however, can damage exposed equipment quickly. Backflow preventers, above-ground pipes, hose connections, and valve boxes near the surface are especially vulnerable.
Homeowners in mild climates may not need a full compressed-air blowout every year. If freezes are rare and short-lived, shutting off water and draining exposed components may be enough. In colder regions, a complete winterization is the safer choice.
How to Winterize a Sprinkler System Step by Step
Before starting, locate your irrigation shutoff valve, controller, backflow preventer, drain valves, and zone valves. If you are not sure where those parts are located, avoid guessing. A professional can identify the system layout and make sure the proper valves are being handled.
1. Turn Off the Irrigation Water Supply
Find the dedicated irrigation shutoff valve and close it fully. This valve is often located indoors in a basement, garage, crawl space, or utility area, but it may also be outside near the water meter or backflow device.
Do not assume turning off the sprinkler controller stops the water. The controller only tells the system when to run. The water supply must be shut off at the valve to keep more water from entering the irrigation lines.
If your sprinkler system shares plumbing with other outdoor fixtures, take your time identifying the correct valve. You do not want to accidentally shut down water to part of the home or leave the irrigation line pressurized by mistake.
2. Set the Controller to Off or Rain Mode
Once the water is off, set the irrigation controller to off, rain mode, or seasonal shutdown mode. Most modern controllers keep the date and programming information stored when placed in rain mode, which makes spring startup easier.
Avoid unplugging the controller unless the manufacturer specifically recommends it. Some units can lose programmed schedules when power is removed. If your controller has a backup battery, check it now so it is ready when irrigation season returns.
3. Drain Water From the Backflow Preventer
The backflow preventer is one of the most important components to protect. It is usually installed above ground and prevents irrigation water from flowing back toward the home’s drinking-water supply. Because it is exposed, it can freeze before underground pipes do.
After shutting off the irrigation supply, open the small test cocks or drain ports on the backflow preventer according to the equipment instructions. Then position the shutoff handles at a 45-degree angle rather than fully open or fully closed. This helps relieve pressure and gives any remaining water room to expand.
Some homeowners add an insulated cover after draining the device. A cover can provide an extra layer of protection, but it is not a substitute for removing water. Never wrap a system component so tightly that moisture is trapped against it or access becomes difficult in an emergency.
4. Drain the Irrigation Lines
There are three common ways to remove water from sprinkler lines: manual draining, automatic draining, and compressed-air blowout. The correct method depends on how your system was installed.
A manual drain system has drain valves at low points in the irrigation lines. Open those valves after shutting off the water supply and allow the lines to empty. You may also need to open individual zone valves briefly to release trapped water.
An automatic drain system uses valves that open when water pressure drops. These systems drain on their own after the supply is shut off, although low spots and certain components may still hold water. It is still wise to inspect visible equipment and confirm the backflow device has been drained.
Compressed-air blowout is the most thorough option for colder climates. It pushes water out through each irrigation zone using an air compressor connected at a designated point. It is effective, but it requires the right equipment, safe pressure settings, and a clear understanding of the system.
5. Use Compressed Air Carefully
A sprinkler blowout can damage pipes, valves, fittings, and sprinkler heads if too much air pressure is used or if a zone runs too long. This is where a professional service is often the best choice, particularly for homeowners with larger properties, multiple zones, drip irrigation, or an unfamiliar system.
If your system was designed for a blowout, follow the manufacturer’s pressure guidance. The air supply should be regulated, and zones should be cleared one at a time. You are looking for a visible mist from the sprinkler heads, not a long period of dry, high-pressure air. Once mostly air is coming through, stop that zone and move to the next one.
Never stand over sprinkler heads while a zone is being blown out. Keep children and pets away from the work area, and wear eye protection. Do not use compressed air if you are unsure where the connection point is, how much pressure the system can handle, or whether the backflow assembly needs special handling.
6. Protect Exposed Parts and Disconnect Hoses
After the lines are drained or blown out, disconnect garden hoses from outdoor spigots. A hose left attached can trap water against the faucet and contribute to a freeze-related plumbing issue. Drain the hose, coil it, and store it where it will not sit in standing water over winter.
Check exposed pipes, sprinkler pumps, hose bibs, and irrigation components near the home. Remove standing water from valve boxes if possible, especially if the boxes have poor drainage. A clean valve box is easier to inspect in spring and less likely to conceal a damaged fitting.
Common Winterization Mistakes to Avoid
The most common mistake is shutting off the controller but leaving the water supply on. Another is assuming a few minutes of draining removes all water from a system. Low sections of pipe, valves, and backflow devices can hold enough water to cause damage.
Do not pour automotive antifreeze or any chemical product into an irrigation system. It can harm your lawn, soil, pets, and local water supply. Proper draining or a controlled blowout is the right approach.
It is also easy to overlook drip irrigation. Drip lines, filters, pressure regulators, and emitters need attention just like spray zones do. Some drip systems may require separate draining procedures, so review the installation details before winter arrives.
Is Professional Sprinkler Winterization Worth It?
For a simple system in a mild climate, a homeowner may be comfortable shutting off the water and draining exposed equipment. In areas with sustained freezing temperatures, professional winterization is often a practical investment. Repairing a burst fitting or backflow preventer can cost far more than seasonal service, and hidden pipe damage may not show up until spring.
A contractor can also spot issues that are easier to address during the off-season, such as leaking valves, broken heads, poor drainage, aging backflow equipment, or zones that are not operating correctly. That gives you a clearer picture of what your system needs before watering season begins again.
Your sprinkler system works quietly when everything is right. Give it the same care before winter that you give your lawn in spring, and you can head into the cold season with fewer surprises. If you would rather leave the shutoff, drainage, and system check to a trusted local team, B&W Precision Brothers Contracting is ready to talk through your property and provide a clear custom estimate.