A sprinkler system can spend all summer quietly watering the lawn, then suffer expensive damage during one cold spell. Water trapped inside pipes, valves, sprinkler heads, or a backflow assembly can freeze and expand. A small amount left in the wrong place may be enough to crack plastic fittings, split pipe, or damage parts that are awkward to replace once the ground is frozen.
Winterizing sprinklers is the process of shutting off the irrigation water and removing as much trapped water as the system requires before freezing weather arrives. Some installations drain through valves. Others use automatic drains. Many systems in cold regions are cleared with compressed air. The correct method depends on how the irrigation was installed, so identify what you have before opening valves or connecting a compressor.
High-end contractor pick: Irrigation contractors who service many properties may use an industrial 185 CFM towable air compressor from Amazon. Machines in this class commonly cost far more than $2,000 and supply the high air volume needed for large irrigation jobs. This is not a sensible purchase for most homeowners. Compressed-air winterization can cause injury or sprinkler damage when done incorrectly, so hiring an irrigation contractor is often the better choice.
Winterize Before the First Hard Freeze
Do not wait until frozen ground arrives.
The safest time is during fall after regular lawn watering has ended but before temperatures remain below freezing for long periods.
A brief cold night can damage exposed irrigation parts, especially a backflow preventer sitting above ground.
If freezing weather is forecast sooner than expected, shut off the irrigation water and protect exposed parts even if you cannot complete the full job that day.
People in mild climates may not need a full annual blowout. Homes in regions with regular freezing temperatures usually need more winter protection.
Find the Irrigation Water Shutoff
Your first job is finding the valve that feeds water to the sprinkler system.
Do not confuse it with the main valve that shuts water off to the entire house.
The irrigation shutoff may be in a basement, utility room, crawlspace, garage, valve box, or near the point where the sprinkler line branches from the household plumbing.
Common valve types include ball valves, gate valves, and stop-and-waste valves.
If you are unsure which valve controls irrigation, trace the pipe from the backflow assembly toward the house before turning anything.
Shut Off the Sprinkler Water
Close the irrigation supply valve fully.
For a ball valve, the handle normally sits across the pipe when closed. Do not use excessive force if the valve is stiff.
After closing the water, activate one sprinkler zone briefly from the controller. This can relieve pressure trapped in the irrigation mainline.
The sprinklers may rise for a moment and then stop as pressure falls.
Once pressure has been released, you can move on to the drainage method used by your installation.
Identify Your Sprinkler Drainage Method
Residential irrigation commonly uses one of three approaches:
- Manual drain valves
- Automatic drain valves
- Compressed-air blowout
Some yards use more than one. The mainline might have a manual drain while the lines running to sprinkler heads have automatic drains.
If you inherited the system with the house and cannot tell which method applies, ask an irrigation contractor to inspect it. Guessing can leave pockets of water behind.
How to Winterize Sprinklers With Manual Drain Valves
A manual-drain installation has valves placed at low points where water can leave by gravity.
Start with the irrigation water shut off.
Activate a zone for a short time to release pressure.
Wear eye protection before opening pressurized irrigation parts.
Slowly open the manual drain valves. Water should begin flowing from the low points.
Open every drain installed on the irrigation mainline and lateral piping according to the original installation.
If there is a drain between the indoor shutoff and the exterior backflow assembly, open that as well.
Give the water enough time to stop flowing.
Some sprinkler heads contain check valves that hold water inside the body. Those installations may need extra attention because gravity alone may not remove all trapped water.
Once drainage is complete, return manual drain valves to the position recommended by the irrigation maker or installer.
How Automatic Drain Sprinkler Systems Work
Automatic drains open when water pressure falls below their operating level.
After the irrigation supply is shut off, activate a sprinkler zone to reduce pressure. The automatic drains can then release water from low areas.
Walk around the yard and look for drainage near known valve or sprinkler locations.
A large puddle that continues for an unusual amount of time may point to a drain that is stuck or another fault.
Automatic drains are convenient, but they do not mean every installation is ready for winter with no other work. Backflow equipment, filters, pumps, above-ground pipe, and other parts may still contain water.
When a Sprinkler Blowout Is Needed
Compressed air is commonly used where gravity drainage cannot remove enough water from the pipes.
This is especially common in cold climates and in installations containing check valves.
A compressor pushes air through one irrigation zone at a time. Water leaves through the sprinkler heads until only a light mist remains.
The job sounds simple, but compressed air stores a lot of energy. Sprinkler bodies, valves, fittings, and debris can become dangerous if pressure is too high or a part fails.
Wear approved eye protection and hearing protection. Keep children and pets away. Never stand over a sprinkler head, valve box, pipe fitting, or backflow assembly while compressed air is moving through the irrigation lines.
Pressure Is Not the Same as Air Volume
A common mistake is assuming that more pressure gives a better blowout.
It does not.
Irrigation winterization depends heavily on air volume. Raising pressure far beyond the rating of the sprinkler parts can damage pipes, valves, heads, and fittings.
Rain Bird currently tells homeowners not to exceed 50 PSI during its blowout procedure. Hunter gives limits based on pipe and component ratings and lists 50 PSI for polyethylene pipe in its winterization material.
If the maker of your irrigation parts gives a lower pressure limit, use the lower figure.
Never raise pressure simply because the sprinkler heads are not behaving as expected.
Do Not Blow Air Through the Backflow Preventer
The compressor connection should normally be downstream of the backflow device.
Do not push compressed air through a backflow assembly unless its maker specifically calls for that procedure.
Backflow devices contain internal parts that can be damaged by incorrect compressed-air use.
The backflow assembly needs to be drained separately according to its type.
If you cannot identify the assembly or do not know where a suitable blowout connection is located, hire an irrigation contractor rather than improvising a connection.
Basic Sprinkler Blowout Sequence
If your irrigation maker permits homeowner blowout and you have the correct compressor, fittings, protective gear, and experience, the broad sequence looks like this:
- Close the irrigation water supply.
- Activate a sprinkler zone briefly to relieve water pressure.
- Connect the compressor to the correct fitting downstream of the backflow device.
- Keep the compressor outlet closed while making the connection.
- Open the sprinkler zone farthest from the compressor connection.
- Set the compressor regulator within the pressure limit for your irrigation parts.
- Introduce air slowly rather than opening the compressor valve suddenly.
- Let water discharge through the sprinkler heads.
- Stop the air after a short cycle.
- Move to the next zone.
- Repeat short cycles rather than running one dry zone for a long time.
- Shut the compressor off before disconnecting the hose.
- Release trapped air pressure before touching fittings.
Never leave the compressor running unattended.
Why Short Blowout Cycles Are Better
Once most water has left a zone, continuing to force compressed air through dry pipe does little good.
Air moving through dry irrigation parts can create heat.
Use shorter passes through each zone and come back for another pass if needed.
During the first pass, you may see a steady stream of water from the sprinkler heads. Later passes should produce much less.
Stop once the zone has been cleared according to the sprinkler maker’s directions. Trying to make every sprinkler completely dry by running air for a long period can damage parts.
Work Through Every Sprinkler Zone
Do not stop after the first group of heads looks dry.
Each valve controls its own section of irrigation pipe, and each section can hold water.
Run the winterization procedure through every lawn zone, rotor zone, spray zone, garden section, and other irrigation circuit connected to the mainline.
Make a note of the number of zones before beginning. It is surprisingly easy to skip one when the controller has eight, ten, or twelve stations.
Drain the Backflow Preventer
Above-ground backflow assemblies are especially exposed to cold air.
Water trapped inside can freeze and crack internal parts or the body of the assembly.
After the irrigation piping has been drained, treat the backflow unit according to its maker’s winter instructions.
Pressure vacuum breakers commonly have test cocks and isolation valves that need specific positions for winter drainage.
Do not copy the valve position from a neighbor’s unit unless the two devices are the same type.
If you are unsure how yours should be left, have it serviced by an irrigation or backflow professional.
Insulate Exposed Irrigation Parts
Any pipe, valve, or backflow part that remains above ground may need insulation in freezing weather.
Foam pipe insulation or insulating tape can help protect exposed piping after drainage.
Do not block drain openings or air vents on a backflow device.
Insulation is extra protection. It is not a substitute for draining equipment that was designed to be emptied before winter.
Winterize the Sprinkler Controller
Once the water side is finished, turn your attention to the controller.
Many controllers have an Off, Rain, Standby, or similar mode that prevents normal irrigation cycles while keeping saved schedules available.
Using that setting can make spring startup easier because your watering times may still be stored.
Controller instructions differ by model. Some indoor units can be unplugged for winter, while some outdoor controllers are better left powered with watering turned off.
Check the directions for your exact controller before disconnecting power.
Remember Irrigation Pumps
If your sprinkler system draws water using a pump, that equipment also needs cold-weather care.
Turn the pump off and stop it from starting accidentally.
Pumps, housings, filters, and connecting pipe can hold water after the sprinkler zones appear empty.
Follow the pump maker’s winter procedure. Some units have drain plugs that need to be opened.
Do not run an irrigation pump dry unless the pump maker says that is acceptable.
How to Winterize Drip Irrigation
Drip tubing needs attention too.
Start by shutting off its water supply or isolating the drip zone.
Open flush caps or end closures so water can leave the lines.
Lift low sections of removable tubing gently so trapped water can travel toward an open end.
Remove detachable filters, pressure regulators, timers, and other above-ground parts when their instructions call for indoor winter storage.
Clean removable pieces before storing them in a dry place.
Drip irrigation often runs at low water pressure, but that does not make it immune to freeze damage. Small fittings and emitters can crack when water freezes inside them.
Do Not Forget Hose-End Sprinklers and Timers
A simple garden hose setup needs winter care as well.
Disconnect hoses from outdoor faucets.
Drain the hoses and store them where they will not remain full of frozen water.
Remove battery-operated hose timers and detachable irrigation fittings when recommended by the maker.
Water trapped inside a plastic timer can split the housing during a freeze.
Common Sprinkler Winterizing Mistakes
Waiting until after the first long freeze is one mistake. By then, exposed parts may already be damaged.
Another mistake is shutting off the controller but leaving the irrigation water turned on. A controller in Off mode does not remove water from the pipes.
Using excessive compressor pressure is another problem. High pressure can damage pipe and sprinkler parts without doing a better job of removing water.
Running compressed air through the backflow assembly is also a poor approach unless its maker specifically calls for it.
Homeowners sometimes clear the lawn sprinklers but forget drip lines, outdoor filters, pumps, hose timers, or an exposed backflow device.
The last mistake is continuing to blow air through a dry zone for too long. Once water is gone, extra air can heat and damage irrigation parts.
Can You Winterize Sprinklers Without an Air Compressor?
Yes, if your irrigation was built for manual or automatic drainage and that method removes enough water for your climate.
Some installations are specifically arranged so gravity handles most winter drainage.
Other systems cannot be cleared well enough without compressed air.
This is why knowing how your irrigation was installed matters.
If you do not know, an irrigation contractor can identify drain valves, check valves, backflow equipment, pipe type, and the safest winter method.
When to Hire a Sprinkler Winterization Service
Hiring a contractor makes sense if you do not know where the shutoff or blowout fitting is located.
It is also a good choice if your yard has many zones, a pump, complicated backflow equipment, large irrigation pipe, extensive drip tubing, or a history of freeze damage.
Compressed-air work is another good reason to call a professional when you have never done it before.
A sprinkler company already has the high-volume compressor and fittings needed for the job. You avoid buying or renting industrial equipment for a task done once each year.
Check the Yard After Winterization
Walk around the property once the job is complete.
Look for open valve boxes, loose lids, exposed wiring, disconnected fittings, or irrigation parts left where they could be damaged by snow equipment.
Check that the sprinkler water supply remains closed.
Make a short note on your phone describing which valves were left open, closed, or partly open. Take photos if the backflow valve positions are easy to forget.
Those notes can save time when spring arrives.
Do Not Turn the Sprinklers Back On During a Warm Winter Day
A warm afternoon in January does not mean freezing weather has ended.
Once an irrigation system has been drained for winter, leave it shut down until the main freezing season has passed.
Refilling all the pipes because the lawn looks dry can put water back into vulnerable parts just before another cold night.
If plants need occasional winter water in a mild spell, hand watering may be easier than restarting the entire irrigation system.
Prepare for Spring While You Winterize
Winter shutdown is a good time to note sprinkler problems you noticed during summer.
Write down any broken heads, weak zones, leaking valves, crooked rotors, damaged drip tubing, or areas that received too much or too little water.
You do not need to repair everything during cold weather.
A simple note gives you a ready-made spring job list once irrigation season returns.
A Simple Sprinkler Winterization Order
- Watch the weather and finish winterization before regular freezes.
- Locate the irrigation shutoff valve.
- Turn off the sprinkler water supply.
- Relieve pressure from the irrigation line.
- Identify whether the system uses manual drains, automatic drains, compressed air, or a combination.
- Drain each irrigation section using the correct method.
- Clear every sprinkler zone where compressed-air blowout is required.
- Drain and protect the backflow assembly.
- Winterize pumps, filters, and drip components.
- Protect exposed pipe where needed.
- Place the controller in its winter or off setting.
- Record valve positions for spring startup.
Give Freezing Water Nowhere to Hide
The goal of sprinkler winterization is straightforward: stop new water from entering and remove enough trapped water to prevent freeze damage.
Begin at the irrigation shutoff. Find out how your pipes were designed to drain. Pay attention to the backflow assembly, sprinkler heads, valves, drip sections, pumps, and above-ground fittings rather than thinking only about buried pipe.
If compressed air is required, treat it with respect. Use the pressure limit called for by the irrigation parts, keep people away from pressurized components, and stop once each zone has cleared. When the setup is unfamiliar, paying a sprinkler contractor for an annual blowout can be far cheaper than replacing cracked valves and broken pipe in spring.
Winterizing may take less than an afternoon, yet it protects equipment that stays buried and forgotten for months. A dry sprinkler line can sleep through winter without much drama. A pipe full of water is a different story once the temperature drops below freezing.