Utah homeowners blow out sprinkler lines with compressed air each October, after secondary water shuts off around mid-October and before hard freezes. Skipping it can crack lines, valves and the backflow assembly. The damage usually shows up in April, when water returns, sometimes as a leak beside the foundation that seeps into a basement.
Key takeaways
- Secondary (pressurized irrigation) water in many south-valley and Utah County cities typically shuts off in mid-October and comes back in mid-April; check your own city's notice for exact dates.
- A blowout pushes the standing water out of sprinkler lines, valves and heads with compressed air so it cannot freeze and crack them over winter.
- The above-ground backflow assembly, often a pressure vacuum breaker, is one of the most freeze-prone parts of the system because it sits exposed beside the house.
- Freeze damage from a missed blowout usually stays hidden until spring start-up, when a cracked line or fitting can soak the soil beside the foundation and leak into a basement.
- If sprinkler water reaches the basement, turn off the irrigation supply or controller and get wet carpet and drywall drying within 24–48 hours, as the EPA advises.
When should you blow out sprinklers on the Wasatch Front?
Most Wasatch Front homeowners blow out sprinklers in October, soon after secondary water shuts off around mid-month and before the first hard freeze. Culinary-fed systems follow the same window. Waiting until November risks an overnight hard freeze cracking the above-ground backflow assembly, which is the most exposed part of the system.
Secondary water is the separate pressurized irrigation many south-valley and Utah County cities run for lawns and gardens. It typically goes off in mid-October and comes back in mid-April, but dates vary by city and by year, so watch for your own city's or irrigation company's notice.
In the south valley that water is often fed from canals, and seven irrigation canals serving the Salt Lake Valley begin at the Jordan Narrows on Bluffdale's south end. When the supply stops, the pipes under your lawn still hold whatever was in them, and that leftover water is what freezes.
| Month | What is happening | Sprinkler task |
|---|---|---|
| September | Cooler nights; lawns need less water | Shorten run times and note any heads or zones that misbehaved over summer |
| Early October | Secondary water still on in most cities | Book a blowout before the rush and disconnect garden hoses |
| Mid-October | Secondary water typically shuts off | Blow out every zone and drain or insulate the backflow assembly |
| Late October–November | First freezes, then first hard freezes | Confirm the controller is off and the backflow is left as your installer advised |
| December–February | Deep cold and freeze-thaw cycles | Leave the system alone and keep the backflow cover in place |
| March | Snowmelt soaks yards and window wells | Check that soil near the foundation slopes and drains away from the house |
| Mid-April | Secondary water typically returns | Open the supply slowly, run each zone and look for leaks near the house |
| May | Full watering season begins | Watch for soggy spots that never dry and heads that lose pressure |
What does a sprinkler blowout actually do?
A blowout pushes compressed air through each sprinkler zone so the standing water inside pipes, valves and heads is forced out through the heads. Buried lines dip and rise with the yard, and every low spot holds water that can freeze, expand and split the pipe or crack a fitting over winter.
The air goes in at a blowout port downstream of the backflow assembly, then each zone valve is opened in turn until the heads spit only mist. Forcing air backward through the backflow device can damage it, which is one reason many homeowners hire the job out.
Too little air volume leaves water in the far end of long zones, and too much pressure can blow apart fittings or pop heads. Sprinkler companies and landscapers bring compressors sized for the work and know how long each zone needs.
Some systems have drain valves at low points that empty the lines on their own. Those still benefit from a blowout here, because heads, valve manifolds and any section that does not slope to a drain can trap water.
Bluffdale Water Damage Restoration does not do sprinkler blowouts or sprinkler repair. The restoration crew comes in when a cracked line or backflow leak has put water where it does not belong: inside the house.
How do you winterize a sprinkler system, step by step?
Shut off the irrigation supply, set the controller to off, blow out each zone from the blowout port, then open the backflow assembly's test cocks and leave its valves as your installer recommends so trapped water can escape. Disconnect garden hoses the same day. Hire it out if you lack a properly sized compressor.
Write down how the backflow valves were left and where the blowout port is. Next April, whoever turns the system back on will need to close the test cocks and open the valves slowly, in the right order.
Hose bibs and sprinklers fail in the same cold snaps, so it pays to handle both on one October afternoon. The frozen and burst pipes guide covers the indoor side of winter prep.
| Step | What to do | Why it matters |
|---|---|---|
| 1. Shut the supply | Close the irrigation shut-off, often in a valve box in the yard or in the basement where the sprinkler line leaves the house | No new water can refill the lines once they are cleared |
| 2. Turn off the controller | Set the timer to off or rain mode | Stops valves from opening on a schedule all winter |
| 3. Relieve pressure | Run a zone briefly or open a drain valve | Makes connecting the compressor safer |
| 4. Blow out each zone | Connect the compressor at the blowout port after the backflow and run each zone until the heads show only mist | Clears the low spots where water would freeze |
| 5. Open the backflow test cocks | Open the small test cocks and leave the ball valves part-way open, as many installers advise | Lets water drain out of the brass body instead of cracking it |
| 6. Insulate the backflow | Cover it with an insulated pouch or wrap that is easy to remove | Shields the most exposed part from wind and deep cold |
| 7. Handle the hose bibs | Disconnect and drain hoses; close any indoor shut-off for outdoor faucets and open the spigot outside | A hose left on traps water in the faucet and the pipe behind it |
Why is the backflow assembly so easy to freeze?
A sprinkler backflow assembly, often a pressure vacuum breaker, sits above ground beside the house, so wind and cold reach it directly. Its brass body, bonnet and internal check hold small pockets of water after the season. When that water freezes, it can crack the body or bonnet, and the leak appears when water returns in spring.
The device exists to stop irrigation water, which can carry fertilizer and soil, from flowing back into the drinking water supply. That is why it is usually installed where a sprinkler system connects to culinary water, often a few feet from a foundation wall.
Placement is what turns a sprinkler problem into a basement problem. A cracked bonnet sprays the siding and soaks the soil right along the foundation, and if a basement bedroom or window well sits on that side, the water follows the easiest path inside.
Trouble at spring start-up looks like water spraying or dribbling from the top of the assembly, a steady hiss, weak pressure in every zone, or a puddle that refills after you mop it. Shut the irrigation supply right away and call a sprinkler contractor or plumber for the repair, and ask your city or water provider whether the assembly needs testing once it is fixed.
How does a cracked sprinkler line end up in your basement?
A line or fitting cracked over winter usually leaks underground, so the first sign is often inside, not in the lawn. Water runs along the foundation, collects in the backfilled soil and window wells, and seeps through cracks, the wall-floor joint or a window into finished basement rooms, sometimes days after start-up.
Backfill against a foundation is looser than undisturbed ground, so water travels through it easily. Zones that water the beds along the house put heads and lines within a few feet of the wall, which is why a small crack there matters more than one out by the sidewalk.
April timing muddies the picture. Valley snowmelt and spring rain soak yards at the same time, and from May into June rising groundwater can push water into basements on its own, so a wet carpet near a window well is not always the sprinkler's fault. The crew's moisture mapping with meters and thermal tools helps show where the water entered.
Water that has run through soil is not clean supply water. The crew treats it with more caution than a leak from a kitchen line, and pad and drywall it soaked are more likely to come out rather than be dried in place.
What should you check when the sprinklers come back on in April?
Close the backflow test cocks, open the irrigation supply slowly and watch the assembly for leaks before running any zones. Then run each zone one at a time, walk the yard, and look closely at heads and soil along the foundation. Check the basement walls and window wells that same day and again two days later.
The EPA's WaterSense program recommends a spring check-up for irrigation systems, looking for leaks, broken or clogged heads, and spray landing on the house or pavement instead of the plants. On the Wasatch Front, adding a basement walk-through to that list is the local twist.
Heads aimed at the foundation are worth fixing even without a leak. Spray that soaks siding and window wells every morning all summer adds water exactly where a basement can least afford it.
- A geyser, bubbling soil or a head that barely pops up usually means a broken line or fitting in that zone
- A soggy patch that stays wet while the zone is off points to a leak under it
- Water standing in a window well after a sprinkler cycle, with no rain, is a warning sign
- Damp carpet, swollen baseboards or a musty smell in a basement room on the sprinkler side of the house
- Low pressure across every zone can mean a crack at the backflow or the main irrigation line
What should you do if sprinkler water is already in the basement?
Turn off the irrigation supply or the controller first, and stay out of standing water near outlets, cords or the furnace. Photograph the wet rooms and the outside spot where the leak is. Then get extraction and drying started, since the EPA advises drying water-damaged areas within 24–48 hours to prevent mold.
Sprinklers usually have their own shut-off, and on secondary water the house main will not stop them at all. If you cannot find the irrigation valve, switch the controller off so no zone runs again, then call a sprinkler contractor for the repair.
Inside, the crew extracts water, checks walls and floors with moisture meters and thermal tools, pulls wet pad and baseboards, and dries the room with air movers and dehumidifiers. Call (650) 587-4092 at any hour; a crew is dispatched as fast as one is available. The basement flooding cleanup page explains each step.
Insurance may treat outside water differently from a pipe that bursts inside the house. Seepage through soil can be handled as gradual damage or surface water under many policies, so ask your agent before assuming anything. The crew can supply photos and moisture readings for the claim, and coverage is decided by your insurer.
Frequently asked questions
Do I still need a blowout if my city's secondary water is already off?
Yes. Turning off the supply stops new water, but the pipes, valves and heads keep whatever was in them when it shut off. Those pockets are what freeze, so the lines still need clearing with air before the hard freezes arrive.
Is it too late to blow out sprinklers after the first frost?
Usually not. A light frost rarely reaches buried lines, but the above-ground backflow assembly feels it first, so blow out as soon as you can and drain or cover the backflow in the meantime. After a deep hard freeze, plan a careful check in April.
Can I blow out my own sprinklers with a small shop compressor?
Small compressors often lack the air volume to clear a long zone, so water stays in the far end even though the gauge looks fine. Too much pressure can crack fittings, too. Many Utah homeowners hire a sprinkler company or landscaper for the job each October.
Who fixes a cracked backflow assembly or sprinkler line?
A sprinkler contractor or plumber repairs the backflow and the lines. Bluffdale Water Damage Restoration does not repair sprinklers; the crew handles water that got into the house, from extraction and drying to replacing drywall, trim and flooring once the rooms are dry.
Why does my window well fill up when the sprinklers run?
Heads may be spraying into it, or a leak nearby is soaking the backfill around the foundation. Redirect any head aimed at the well, check that zone for a broken line, and clear the well's drain if it has one. A full window well can push water through the basement window.
Sources
- U.S. EPA WaterSense – Sprinkler Spruce-Up
- U.S. EPA WaterSense – Fix a Leak Week
- U.S. EPA – A Brief Guide to Mold, Moisture, and Your Home
This guide is general information for Salt Lake County homeowners, not a substitute for an on-site inspection. Prices are estimates. See our disclaimer.