Before you begin. This procedure is general reference information, not professional advice. Equipment varies by manufacturer, model, and year. Always follow the documentation supplied with your equipment — where it differs from this page, follow the manufacturer. Verify that you have the tools, the working conditions, and the ability to do this task safely. If anything is unclear, if the equipment is damaged, or if the task exceeds your experience, stop and use a qualified professional. You are responsible for your own safety and for the outcome. This site accepts no liability for any loss, damage, or injury arising from the use of this information.
Specifications marked unverified could not be traced to a manufacturer source. Do not rely on them — obtain the value from your equipment documentation.
Summary
An underground irrigation system drains water from its pipes in one of three ways: a manual drain valve you open by hand, an automatic drain valve that opens on its own, or a compressed-air blow-out. Rain Bird's own guide says some properties use a combination — a manual valve on the mainline and automatic valves on the lateral lines running out to the heads. This page covers the first two methods: finding your drain valves, shutting off the water supply, draining the mainline and the backflow preventer, and setting the controller for winter. If your property has both types of valve, expect the job to run toward the longer end of the time estimate below.
The compressed-air method is not covered here as a set of steps. Rain Bird's and Hunter Industries' own guides both recommend hiring a licensed irrigation contractor for it, and the two guides do not agree on the maximum air pressure to use — Rain Bird caps it at 50 psi for any system, Hunter Industries allows up to 80 psi for rigid PVC pipe. Where two manufacturers publish different numbers for the same job, this page does not pick one; it sends you to a professional instead, and Professional boundary explains why.
Safety
RELIEVE THE PRESSURE IN THE MAINLINE BEFORE YOU OPEN A DRAIN VALVE, A DRAIN CAP OR A TEST COCK.
Trapped water can spray out and injure your eyes.
DO NOT CLEAR THIS SYSTEM WITH COMPRESSED AIR YOURSELF.
Compressed air can drive debris into your eyes and cause serious injury.
Necessary equipment
| Item | Note |
|---|---|
| Eye protection | Wear eye protection before you open a drain valve, a drain cap or a test cock. |
| Adjustable wrench or pliers | Use the tool to turn a stiff drain cap or test cock. |
| Small container | The container catches water from the drain cap and the test cocks. |
| Cloth | Put the cloth below a valve to keep the area dry. |
| Flashlight optional | A basement or a valve box can be dark. |
Specifications
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
Find your drain method
Estimated 4 min to 8 min
- Find the low points of the pipe on your irrigation system.3mReport a problem with step 1, Find your drain method
- A manual drain valve is a ball valve, a gate valve, a stop-and-waste valve or a drain cap.
- An automatic drain valve is a small spring-loaded fitting screwed into the pipe or a sprinkler head.
- If you have a hand valve or a drain cap, read the steps for a manual drain.<1mReport a problem with step 2, Find your drain method
- If you have a spring-loaded fitting, read the steps for an automatic drain.<1mReport a problem with step 3, Find your drain method
- Some properties use a manual valve on the mainline and automatic valves on the lateral lines.
- Read both sets of steps for a property like this.
- If you find no drain valve of either type, stop this procedure.<1mReport a problem with step 4, Find your drain method
- This page does not cover the compressed-air method.
- Read Professional boundary before you continue.
Close the water supply
Estimated 2 min to 5 min
MAKE SURE THAT THE VALVE CONTROLS THE IRRIGATION LINE BEFORE YOU CLOSE IT.
A closed valve on the wrong line can stop water at another fixture.
- Close the mainline shut-off valve for the irrigation system.2mReport a problem with step 1, Close the water supply
- The valve is usually indoors, near the point where the line enters the building.
- Open one control valve to relieve the pressure in the mainline.1mReport a problem with step 2, Close the water supply
- Open the valve by hand, or run one station from the controller.
Drain the mainline through a manual valve
Estimated 10 min to 22 min
DO NOT FORCE A VALVE THAT DOES NOT TURN.
An old valve can break in your hand and release water with no warning.
- Open each manual drain valve slowly.3mReport a problem with step 1, Drain the mainline through a manual valve
- Open one valve at a time.
- Water can flow quickly from a valve close to the mainline.
- Wait until water stops running from each open valve.2mReport a problem with step 2, Drain the mainline through a manual valve
- Open the drain cap on the shut-off assembly.2mReport a problem with step 3, Drain the mainline through a manual valve
- This drain point is usually between the mainline shut-off valve and the backflow preventer.
- Let the mainline drain fully.2mReport a problem with step 4, Drain the mainline through a manual valve
- Close each manual drain valve.2mReport a problem with step 5, Drain the mainline through a manual valve
- Close each valve after the water stops.
Look at the automatic drain valves
Estimated 4 min
Source: Winterizing Your Irrigation System · tier 1 · accessed 2026-08-04
- Make sure that water drains from each automatic drain valve.2mReport a problem with step 1, Look at the automatic drain valves
- Each valve opens on its own when the pressure in the pipe is below 10 psi.
- No manual action opens an automatic drain valve.
- Look at the soil surface near each automatic drain valve.2mReport a problem with step 2, Look at the automatic drain valves
- A puddle near a valve can mean the valve did not close fully.
Drain the backflow preventer
Estimated 4 min to 6 min
Source: Homeowner's Guide to Winterization · tier 1 · accessed 2026-08-04
- Find the test cocks and the isolation valves on the backflow preventer.2mReport a problem with step 1, Drain the backflow preventer
- Open the test cocks to drain trapped water from the backflow preventer.2mReport a problem with step 2, Drain the backflow preventer
- Turn each ball-type isolation valve to a 45 degree angle.1mReport a problem with step 3, Drain the backflow preventer
- Do this after the water drains from the backflow preventer.
- Leave the test cocks open for the winter.<1mReport a problem with step 4, Drain the backflow preventer
Drain a sprinkler head with a check valve
Estimated 5 min to 9 min
- Look at your sprinkler heads for a check valve.2mReport a problem with step 1, Drain a sprinkler head with a check valve
- A check valve holds the water in place between cycles.
- A check valve is common on a head set higher than the other heads on its line.
- Lift each head with a check valve.3mReport a problem with step 2, Drain a sprinkler head with a check valve
- Lift the head to drain water from the bottom of the head body.
Set the controller for winter
Estimated under a minute
- Turn the controller dial or switch to the OFF or the RAIN setting.<1mReport a problem with step 1, Set the controller for winter
- Leave an outdoor controller connected to power for the winter.<1mReport a problem with step 2, Set the controller for winter
- Heat from the transformer keeps the inside of the enclosure dry.
- The OFF setting stops the controller from opening a valve.
Record the work
Estimated under a minute
- Write the date of this work and your drain method in your records.<1mReport a problem with step 1, Record the work
Terminology
This page uses one term for each item and holds it throughout, as ASD-STE100 requires. Equipment sellers and other guides use the names below for the same parts.
- garden irrigation system
- Also called: sprinkler system, in-ground sprinklers, lawn sprinkler system, yard sprinklers, underground sprinklers, irrigation system
- manual drain valve
- Also called: hand drain valve, boiler drain, stop and waste valve, drain cap, the valve you turn by hand
- automatic drain valve
- Also called: auto drain valve, auto drain, spring-loaded drain, self-draining valve, freeze drain
- backflow preventer
- Also called: backflow device, pressure vacuum breaker, PVB, anti-siphon valve, vacuum breaker
- compressed-air blow-out
- Also called: sprinkler blowout, blowing out the sprinklers, blow out the lines, air compressor winterization
- irrigation controller
- Also called: sprinkler timer, irrigation timer, sprinkler clock, the box that runs the sprinklers
When to use a professional
Stop if you plan to clear the system with compressed air. Rain Bird and Hunter Industries both recommend a licensed irrigation contractor for that method. Compressed air moves through the pipe far faster than water. The wrong pressure or the wrong volume can crack a pipe or a fitting. It can also drive debris into a person's eyes. This page gives no steps for the compressed-air method.
Stop if you find no manual drain valve and no automatic drain valve. If you guess at a drain point, water can stay in the pipe over winter. Call an irrigation contractor to identify your system or to drain it for you.
Stop if a valve does not turn, or if it leaks after you close it. Do not force it. Call a plumber or an irrigation contractor before the first freeze.
Stop if a pump feeds your system and your controller connects to house wiring outdoors. Do not open the main breaker panel by yourself. Call an electrician or an irrigation contractor to disconnect the controller safely.
Stop if you see a crack in a pipe, a valve or the backflow preventer body. A cracked part can fail without warning when the water returns in spring. Call a plumber or an irrigation contractor before you use the system again.
Stop if your system is a drip irrigation system with narrow tubing and emitters rather than pipe and sprinkler heads. This page does not cover that equipment. Look at the instructions for your drip system instead.
Common questions
How do I know if my sprinkler system has a manual or an automatic drain?
Look at the low points of the pipe, usually near the mainline valve and at the end of each zone. A manual drain is a valve you turn by hand, or a threaded cap you unscrew — a ball valve, a gate valve or what is often called a stop-and-waste valve. An automatic drain, which Rain Bird sells as its model 16A-FDV, is a small spring-loaded fitting screwed into the pipe or the bottom of a sprinkler head; it opens on its own once the line pressure drops below 10 psi. Some properties use both: a manual valve on the mainline and automatic valves on the lateral lines out to the heads. If you cannot find either type, do not guess — an irrigation contractor can identify your system.
What is a safe psi for blowing out a sprinkler system?
The two manufacturers behind this page do not agree, which is exactly why this page does not walk you through the compressed-air method. Rain Bird's own Homeowner's Guide to Winterization says air pressure 'must not exceed 50 pounds per square inch (psi)' for any system. Hunter Industries' guide allows more for rigid pipe: 'Do not allow the air pressure to exceed 80 PSI for systems with PVC piping and 50 PSI for systems with polyethylene piping.' Using the wrong number for your pipe material and your equipment can crack a pipe or blow a fitting apart. Both manufacturers recommend hiring a licensed irrigation contractor for this step, and so does this page.
Can I blow out my own sprinkler system with an air compressor?
This page does not walk you through it, on purpose. Both Rain Bird and Hunter Industries recommend a licensed contractor for the compressed-air method, and their own guides carry capitalized warnings about eye protection and, in Rain Bird's words, 'SERIOUS PERSONAL INJURY.' The two manufacturers also publish different maximum pressures and different compressor sizes for what looks like the same job, which is a sign the details matter more than a short guide can safely cover. If you still want to do it yourself, read a manufacturer's full guide first and match the pressure limit to your own pipe material, not to a number taken from a different brand's guide.
Do I need to drain the backflow preventer separately?
Yes. Draining the pipe by gravity does not remove the water trapped inside the backflow preventer itself. Open its test cocks to let that water out, then leave the ball-type isolation valves at roughly a 45 degree angle for the winter — both Rain Bird and Hunter Industries give this same figure, so it can drain the seal area without trapping standing water against it. Leave the test cocks open until spring.
When should I winterize my irrigation system?
Before the first hard freeze in your area, which in most of the northern United States and Canada falls sometime in autumn. None of the sources behind this page gives a specific temperature or a calendar date, and a single number would not be right in every climate anyway. The safer trigger is the weather forecast, not the calendar: if a hard freeze is forecast and you have not winterized yet, do it now rather than waiting for a particular week.
What is a check valve on a sprinkler head, and do I need to do anything extra for it?
A check valve is a small part inside some sprinkler heads that stops water already in the pipe from draining out through the lowest head every time the zone shuts off. It is common on heads set higher than others on the same line. Rain Bird and Hunter Industries both say to lift these heads by hand after you drain the line, which lets the trapped water run out of the bottom of the head body. A head that was cleared using the compressed-air method does not usually need this extra step.
My controller is wired to a well pump. Does this page still cover it?
Most of it does — shutting off the mainline and draining the valves and the backflow preventer is the same job either way. The controller step is where it differs. Do not open a breaker panel yourself to disconnect a pump-fed, hard-wired outdoor controller. Read Professional boundary, and call an electrician or an irrigation contractor for that part instead.
Related procedures
- How to start up a garden irrigation or sprinkler system in spring
- How to winterize an outdoor faucet so it does not burst in winter
- How to winterize a pressure washer pump before freezing weather, and what to put in it
- How to fix an outside tap that drips or won't shut off by replacing the washer and the packing inside the stem
- How to clean out a sump pump pit and check the check valve so the pump stops cycling
Sources
Every specification on this page is traced to one of these sources. Tier 1 is a manufacturer document, a published standard, or a government safety authority. See Standards for the full tiering rule.
- Tier 1Homeowner's Guide to Winterization
- Tier 1Winterizing Your Irrigation System
- Tier 1Maintenance Checklist for a Water-Efficient Home
Revision history
Current version 2 · updated 2026-08-04 · next review due 2027-08-04
- v2 · 2026-08-04The automatic-drain opening pressure was published as Rain Bird's figure. It is not in the Rain Bird guide. That document was fetched and read in full today: its Automatic Drain Valve section says only 'The drain valve will open every time the system is shut off' and 'When the system is pressurized, the water shuts the valve off by pressing against the sealing mechanism' — no opening pressure anywhere, and the only psi figures in the whole guide are the 50 psi blow-out ceiling and a 120 psi warning. The sentence the value rests on is Hunter Industries', verbatim, also fetched and read today: 'These will automatically open and drain water if the pressure in the piping is less than 10 PSI.' Re-attributed to Hunter, and the value now carries the source's own 'less than' rather than 'drops below'.
- v1 · 2026-08-04First draft. Sourced to Rain Bird's Homeowner's Guide to Winterization and Hunter Industries' Winterizing Your Irrigation System, both read in full as manufacturer PDFs, plus EPA's WaterSense home maintenance checklist for the annual-task context. The manual drain and the automatic drain methods are instructed as steps; the compressed-air blow-out method is not, because both manufacturers recommend a licensed contractor for it and because the two publish different maximum pressures (50 psi Rain Bird overall; 50 psi or 80 psi Hunter Industries, split by pipe material) and different compressor sizes (10-25 CFM Rain Bird; 80-100 CFM Hunter Industries) for the same job. Both conflicts are recorded as conflict_note rather than reconciled, and professional_boundary and two FAQ answers route the reader to a contractor instead of printing a chosen number. A pump-fed, hard-wired, outdoor controller requires disconnecting a common wire at the main circuit breaker panel per Rain Bird's own guide; that step is excluded work and is named only in professional_boundary, never instructed. No Toro source is cited: the Toro documents found during research were either a golf-course and commercial-turf guide (Toro Advantage, an official Toro Company site explicitly scoped to golf course superintendents) or third-party summaries of it, and carrying a commercial-scale figure onto a residential garden system risked exactly the scope mismatch this repository exists to avoid.
Corrections to this page are listed in the public corrections log. Reports that are credible and not yet verified are listed in the public errata register, and an open one renders above the step it concerns.
Comments and corrections
Found an error? A correction with a manufacturer source is applied and logged publicly. You can also write to corrections@fixchecklist.com.
Every step above carries its own report control, which tags the report with that step so a correction reaches the right place. For anything about the procedure as a whole — the order of the sections, a step that is missing, something that did not match your equipment — use this: report something about this whole procedure.