SPRINKLER BLOWOUT GUIDE • BISMARCK, ND
When to Blow Out Your Sprinklers in Bismarck
Blow out your sprinklers before the first hard freeze, when temperatures drop to about 28°F or lower. In Bismarck, that usually means late September through mid-October.
Bismarck’s first frost averages around September 20 to 25. Fall 2026 may run late, though. A late-August 2026 outlook from a Bismarck radio station, based on AccuWeather, put this year’s first frost near October 9 and the first hard freeze near October 11. Forecasts change, so watch the 10-day forecast and book your blowout before the first night in the 20s.
BEFORE THE FIRST HARD FREEZE
Frost vs. Hard Freeze: What Actually Hurts Your Sprinklers?
| Frost | Hard freeze | |
|---|---|---|
| Temperature | Around 32°F | About 28°F or colder |
| What it does | Kills tender plants and annual flowers | Freezes water in pipes and fittings |
| Risk to sprinklers | Low for one short night | High, especially for parts above ground |
The backflow preventer is the part most at risk. It sits above ground, usually next to the house, with water trapped inside. It’s often the first part to crack when a hard freeze hits. Buried pipes and valves have some protection from the soil, but a long cold snap reaches them too.
THE WARNING SIGNS
Signs It's Time to Blow Out Your Sprinklers
- 01The 10-day forecast shows nights at 28°F or lower
- 02Your lawn has mostly stopped growing, and the final mow is done
- 03The leaves are mostly down
- 04You haven’t needed to water in a week or two
- 05It’s October, and you haven’t booked yet
If two or more of these are true, it’s time. In Bismarck, blowout schedules fill up fast once the first cold snap shows up in the forecast. Our FAQ answers other local yard care questions.
COLD-WEATHER PROTECTION
Why a Blowout Matters So Much in Bismarck
Water expands when it freezes. In a sprinkler system, that means cracked pipes, split fittings, broken valves and a damaged backflow preventer.
In a lot of places, a light freeze is the worst winter brings. Bismarck is different. January lows average about 2°F, and the frost goes deep into the ground. Any water left in the lines has months to freeze, thaw and freeze again.
The damage usually stays hidden until spring startup, when water starts bubbling up in the lawn or the backflow preventer sprays everywhere. A spring repair almost always costs more than a fall blowout.
THE EIGHT-STEP PROCESS
What Happens During a Sprinkler Blowout
A blowout uses compressed air to push water out of every pipe, valve and sprinkler head. Here’s how it’s done, based on Rain Bird’s winterization steps:
- 01Shut off the water to the sprinkler system at the main shutoff valve.
- 02Connect the air compressor to the blowout point on the system.
- 03Set the air pressure to a safe limit, usually no more than 50 psi.
- 04Start with the zone farthest from the air connection.
- 05Blow each zone for no more than 2 minutes at a time. Longer runs can heat up and damage the pipes.
- 06Repeat each zone two or more times, until only a fine mist comes out of the heads.
- 07Drain and protect the backflow preventer, and insulate valve boxes if needed.
- 08Turn the controller to off for the winter.
Anyone doing a blowout should wear eye protection and never stand over sprinkler heads or other parts while air is running. Browse our yard guides for other seasonal maintenance topics.
SAFE DIY LIMITS
Can You Blow Out Your Own Sprinklers?
You can, but most Bismarck homeowners are better off hiring it out. The problem is the compressor.
Rain Bird recommends a large compressor, 50 to 70 gallons, that can deliver a steady 185 cubic feet per minute (cfm) or more. Weathermatic, another sprinkler maker, says volume should never drop below 50 cfm. Most garage compressors put out far less than that, so they can’t push all the water out, and some water gets left behind to freeze. Weathermatic also recommends using a qualified contractor to winterize a system.
Air Pressure Limits by Pipe Type
Too much air pressure can damage valves and fittings. Weathermatic’s limits depend on the pipe:
| Pipe type | Maximum air pressure |
|---|---|
| PVC (rigid white pipe) | 75 psi |
| Polyethylene (flexible black poly pipe) | 50 psi |
| Not sure what you have | Stay at 50 psi |
Weathermatic warns that pressure over 75 psi can cause air pockets that damage the valves.
SEVEN AVOIDABLE ERRORS
Common Blowout Mistakes
- 01Waiting too long. Late-October calls often land after the first hard freeze.
- 02Using too much pressure. Going over 50 psi on poly pipe, or over 75 psi on PVC, can crack fittings and damage valves.
- 03Using a small compressor. It moves too little air to clear the lines.
- 04Running air too long in one zone. Dry pipe with air rushing through heats up fast.
- 05Forgetting the backflow preventer. It’s the most exposed part of the system.
- 06Leaving the controller on. It can try to open valves all winter.
- 07Not marking heads near the driveway. Snow blowers and plows chew them up. Put in stakes when you blow out. Our snow removal page explains why.
AFTER A COLD SNAP
What If You Missed the First Hard Freeze?
Don’t panic. One cold night doesn’t always crack a system, especially if the days warm up again. Get the system blown out as soon as you can, before a longer cold spell settles in.
In spring, watch closely during startup. Look for water bubbling up in the lawn, a leaking backflow preventer or a zone that won’t hold pressure. Those are signs of freeze damage that needs repair. Our irrigation and sprinkler service handles spring startups and freeze repairs.
NEARBY COMMUNITIES
Blowout Timing in Mandan and Lincoln
Mandan and Lincoln share Bismarck’s weather, so the same timing applies: before the first hard freeze, usually late September through mid-October. The same air pressure limits and steps apply too. For lawn watering after spring startup, read about lawn care in Bismarck.
A blowout is one step in getting your yard ready for winter. Our fall yard checklist for Bismarck covers the rest, and our fall and spring yard cleanup service can handle leaves and the final mow on the same visit.
Questions
Sprinkler Blowout FAQ
Clear answers about frost, hard freezes, safe air pressure, and spring startup.
Have a question that isn’t here?
For more local yard-care answers, explore our guides and FAQ.
When should I blow out my sprinklers in Bismarck?
Before the first hard freeze, when temperatures drop to about 28°F or lower. In Bismarck, that’s usually late September through mid-October. In 2026, a late-August outlook pointed to a first hard freeze near October 11, so watch the forecast and book early.
Is one night of frost enough to damage my sprinklers?
Usually not. A short, light frost around 32°F is far less risky than a hard freeze. A hard freeze at 28°F or colder is the real risk, especially for the backflow preventer, which sits above ground.
What psi should I use to blow out sprinklers?
Stay at 50 psi or lower if you’re not sure. Weathermatic sets the limit at 50 psi for flexible polyethylene pipe and 75 psi for rigid PVC pipe. Rain Bird recommends no more than 50 psi.
Can I use my garage air compressor?
Usually not. Rain Bird recommends a large compressor that delivers 185 cfm or more, and Weathermatic says volume should never be lower than 50 cfm. Most garage compressors put out much less, which can leave water in the lines.
What part of a sprinkler system freezes first?
The backflow preventer. It sits above ground with water inside, so it’s exposed to the cold before buried pipes and valves.
When should I turn my sprinklers back on in spring?
Usually around mid-May in Bismarck, after the risk of a hard freeze has passed. The last spring frost averages around May 12 to 14.
Bismarck Landscape
Get on the Blowout List
Fall 2026 may run late, but the first hard freeze always comes. Get on the schedule now, and we’ll blow out your system at the right pressure, protect the backflow preventer and mark heads near the driveway for winter. Contact Bismarck Landscape, or see our other contact options.