How to Winterize Your Sprinkler System

First: when do you actually need to do this?

The sprinkler winterization deadline is your own first hard freeze, and it moves by more than two months across the country. Enter your ZIP for the window where you live — then work the checklist below inside it.

Equipment checks and winterization planning

1. 🛡️Step 1

   Start from your first freeze date, not from a month

   The deadline is your area's average first fall freeze, and it moves by more than two months between the northern plains and the Gulf coast. About half of years freeze before that average, so these pages set the finish date a fixed 12 days earlier — a planning buffer, not a measured early-freeze date — and open the window about four weeks out.

2. 🛡️Step 2

   Confirm the equipment and method before starting

   Identify the actual equipment models, drain layout and approved winterization method before connecting air or opening a device. A device family or map marker is not enough. If any of these are unknown, have a qualified irrigation or backflow professional assess the system first.

3. 🛡️Step 3

   Shut the irrigation main off and stop the controller

   Close the dedicated irrigation shut-off — usually in a basement, a crawlspace, or a below-grade box near the meter — so the lines cannot refill. With no pump, set the controller to off/rain and leave it powered to retain its program, following the controller manual. For a pump-fed system, follow the pump and controller shutdown instructions; preventing an unintended dry run may require power or pump-start disconnection by qualified service. If the setup is unknown, have a qualified professional establish the procedure.

4. 💧Step 4

   Plan the backflow drainage and air isolation

   Use the exact model’s instructions to separate supply shutoff, pressure relief, assembly and riser drainage, and any isolation needed during air work. Test cocks alone may leave internal water. Do not remove covers, bonnets or checks unless the model’s procedure calls for it; arrange qualified service if the procedure or required drain paths are unclear.

   ⚠️

   A downstream air connection alone does not isolate a backflow assembly. Many manuals require its outlet isolation valve closed during downstream blowout, then returned to its specified storage position afterwards.

5. 💧Step 5

   Choose the method the installation supports

   Gravity drainage needs confirmed drain paths at the low points, suitable slope and separate handling of retained water in valves, heads and backflow components. Automatic drains do not establish that the mainline or every component empties. Blowout is suitable only where the component manufacturers permit air. Drip circuits can have different requirements. If the method is unknown, get a qualified assessment instead of assuming blowout will work.

6. 💧Step 6

   If approved for this system, use regulated air with an open zone

   Follow the equipment-specific connection and isolation sequence. Do not send air through a backflow assembly unless its manufacturer expressly specifies that procedure for the exact model and installation. Keep a zone open from before air starts until the compressor is off. Use adequate delivered airflow at the permitted pressure.

   For systems following Rain Bird’s homeowner blowout method, run each circuit for no more than two minutes per pass, cycle through all circuits at least twice, and finish when only a fine mist remains. Stop dry-air flow; other manufacturers’ cycle instructions differ. This is a zone-clearing endpoint, not confirmation that the backflow, risers or other retained-water spaces are drained; complete their separate procedures.

   ⚠️

   Use air only where the equipment instructions permit it. Keep a zone open from before air starts until the compressor is off; never pressurize closed piping. Stay at or below 50 PSI and any lower component limit. Wear eye protection, keep people away from heads and fittings, and do not continue blowing a dry zone. Stop the compressor and relieve pressure before disconnecting or changing the setup.

7. 🛡️Step 7

   Stop air, relieve pressure, then complete drainage and storage

   Turn off the compressor and relieve remaining pressure before disconnecting or approaching fittings. Finish the model’s required component drainage and service. Backflow manuals commonly specify about 45° for ball valves in winter storage, to avoid trapping water around the ball; follow the exact model for each valve and test cock. That storage position is not the isolation setting for the air phase. Keep the upstream water supply shut off so the system cannot refill. Arrange any required backflow service or retest before returning it to use.

8. 🛡️Step 8

   Finish with the small stuff that also freezes

   Drop and drain any hose-end timers, disconnect and drain every garden hose (a hose left connected keeps the sill cock full and splits it from inside the wall), shut off and drain frost-free hose bibs, and pull drip-system filters and pressure regulators — those hold water and crack as readily as anything else on the property.

9. 🛡️Step 9

   Record what you did and how

   Note which winterization method you used, the date, what it cost, and anything that looked marginal. Next spring's startup is a freeze-damage inspection, and it is far more useful when you can compare against what the system looked like the day you shut it down.

Why some ball valves need a 45° storage position

Water can remain between the ball and valve body in either the fully open or fully closed position. These schematics show why many manufacturers specify a half-open drainage and storage position. Follow the actual model’s instructions: temporary isolation during air work is different, and the upstream water supply stays closed.

Which backflow preventer do you have?

Draining the backflow preventer is the step where generic winterization instructions go wrong, because the four devices found on residential systems are winterized differently. Identify yours, then follow its own sequence.

Unbranded drawing, not one manufacturer's product. A real device carries a cast flow arrow on the body showing which end is the supply. Shut-off handles are drawn in the in-service position. A 45° final storage position applies only where the model’s instructions specify it, after drainage and any air work. These drawings do not identify a model or certify its maintenance procedure.

PVB — Pressure Vacuum Breaker

A PVB is a single brass body on a riser about a foot above the highest sprinkler head, with a domed bonnet on top, two ball valves below it, and two small test cocks on the side. The most common device on residential irrigation in freeze country.

The PVB sits above ground and freezes first.

RPZ — Reduced Pressure Zone assembly

An RPZ is the big one: two check valves in line with a relief valve hanging underneath that occasionally dumps water on the ground. Required where the system carries fertilizer injection or a higher hazard rating, and usually the most expensive device on the property.

The RPZ sits above ground and freezes first.

DC — Double Check valve assembly

A double check is two check valves in a single body with four test cocks and no relief valve underneath. Often installed below grade in a valve box, which is what makes it the least freeze-prone of the four.

The DC usually sits below grade — slower to freeze, not immune.

AVB — Atmospheric Vacuum Breaker

An AVB is the small, simple one — a single brass or plastic body downstream of each valve, with no test cocks and no isolation valves. Usually one per zone rather than one for the system.

The AVB sits above ground and freezes first.

Full drain-down steps for each device →

The parts people actually get stuck on

Sprinkler planning guides do not replace the equipment manuals. Explore the questions that stop people halfway through it — no compressor, an unfamiliar backflow device, what it costs, and whether it genuinely matters where you live — plus the spring half of the same job.

And the spring half of the job

Shutting a system down: what people ask

When should I winterize my sprinkler system?

Open the window about four weeks before your area's average first fall freeze and be finished about 12 days before it — a fixed planning buffer, set early because about half of years freeze before the average. That is August in the northern plains and November on the Gulf coast, which is why a fixed month is the wrong answer. Enter your ZIP in the frost-date tool for the window where you live.

Can one light frost damage my sprinklers?

A brief dip to 32°F usually will not reach buried pipe. Whether a colder night does depends on how long the cold lasts and on how deep and well covered the pipe is, so no single temperature decides it. The backflow preventer is the exception: it is above ground, exposed, and full, and it can be damaged by the first real freeze of the season.

Do I have to blow it out, or is draining enough?

Whether draining is enough depends on the sprinkler installation and components. Confirm drain locations and slope, plus the separate drainage needs of valves, heads, risers and backflow equipment. Neither gravity drainage nor blowout is a complete method for every system. If the model or installation is unknown, have a qualified professional choose and perform the method.

What pressure should I use to blow out sprinklers?

For equipment confirmed suitable for air, keep 50 PSI as the upper cap: Rain Bird’s homeowner guide uses that ceiling, and Hunter and Colorado State guidance also set it for flexible polyethylene blowout. It is a blowout limit, not a pipe water-pressure rating or proof any setting is safe. Stay below any lower component-manufacturer limit. If you cannot establish the limits and required air volume for the installation, use qualified help; do not increase pressure to compensate for inadequate airflow.

What does it cost to have it done?

A professional blow-out typically runs $50–250 depending on zone count and region. Freeze repairs typically run $170–$2,500+, and the backflow preventer alone can account for most of that, which is the whole economic argument for doing it.

What if I already had a freeze and never winterized?

If a freeze reaches an un-winterized sprinkler system, shut the system off, drain what you can, and leave it depressurised until spring. Damage from a freeze usually does not show itself until the system is pressurised again, so the worst thing you can do now is turn it back on to check. Plan a careful spring startup with a freeze-damage inspection instead.

Get the reminder without scrolling back up

Enter your ZIP and we’ll set up the same reminder the ZIP tool at the top of this page offers, timed to when it actually matters for your area.

Check the instructions for your equipment

The equipment-manufacturer guides below explain the differences discussed here. Use the current instructions for your exact model, size and installation; an example for another device is not a procedure for yours. If you cannot verify them, use qualified service before connecting air or opening parts.

• FEBCO 765 winterization — IS-F-765-Winterization 2043 (2020), pages 1–2
• Zurn 950/950XL and 975/975XL freeze protection — Rev. C (July 2017)
• FEBCO 850/LF850 Small and 860/LF860 Small (½–2 in.) — 2344 (2023), pages 1–2
• Watts 800M4/LF800M4 — RP/IS-800M4 2409 (2024), Freeze Protection, page 2
• Rain Bird homeowner winterization guide — pressure and valve drainage, pages 3–6
• Hunter winterization guidance — component limits and air precautions

Where this guidance comes from

The university extension and public-agency publications listed here back specific statements on this page. Each publication says which statement it backs, so you can check the statement rather than take it on trust. Where a product label or your local extension office disagrees with anything here, follow the label or the extension office.

• Home Sprinkler Systems: Preparing Your Sprinkler System for Winter (Fact Sheet 4.719)

  Colorado State University Extension

  Water expands as it freezes and splits pipes, valves and heads; gravity drainage needs pipe laid to grade, and blowout air is capped at 50 psi for flexible polyethylene pipe.

• Properly preparing irrigation systems for winter

  University of Minnesota Turfgrass Science

  Sprinkler systems are not all the same, which is why the page asks you to confirm the equipment and method first and treats the exposed backflow area as the most freeze-prone part.

• National Weather Service Glossary: Freeze / Hard Freeze

  NOAA National Weather Service

  A hard freeze is 28°F or lower for an extended period — the threshold behind the page's point that a brief dip to 32°F is not what usually reaches the system.

• 1991-2020 U.S. Climate Normals: Annual/Seasonal Normals Documentation

  NOAA National Centers for Environmental Information

  The local planning date comes from NOAA's 1991–2020 freeze normals, specifically the median (50% probability) date of the first fall 32°F freeze at each station.