Winterizing Home Irrigation Systems: The Step That Prevents Cracked Lines

I decide between a blowout, manual draining, and simply shutting the system down by looking at three things: how cold the site gets, how long freezes last, and where the vulnerable components sit. The important distinction is not just whether temperatures reach freezing, but whether they remain below freezing long enough for trapped water in pipes, valves, drip lines, or the backflow device to freeze solid.

For a property that sees sustained hard freezes—especially where the frost line can reach the irrigation piping—I would recommend a professional full blowout. It is the most reliable way to clear water from zones that do not drain naturally, including systems with electric valves, long runs, uneven grades, or drip irrigation. In milder climates with brief, occasional freezes, shutting off the irrigation supply, opening the manual drains at low points, and draining the backflow assembly can be sufficient. In warm climates where freezes are rare, the focus may be on shutting off the supply and protecting exposed components rather than blowing out every underground line.

The one step that most consistently prevents expensive spring leaks is draining the backflow preventer completely after the supply is shut off. People often remember the sprinkler heads but overlook the above-ground backflow device, where water can remain trapped in small internal chambers. I shut off the irrigation supply, relieve the pressure, open the test cocks or drain ports, and make sure the device is empty before insulating exposed components. That small check protects one of the most freeze-sensitive and costly parts of the system.

As a designer, I also think about winterization as part of the larger outdoor plan. Irrigation valves, backflow assemblies, and lighting transformers should be accessible, labeled, and kept clear of dense planting. A landscape is lower stress to maintain when seasonal service does not require digging through shrubs or moving hardscape elements just to reach critical equipment.

— Jake Woods
Lighting & Interior Designer, Residence Supply

Operating across Northeast Ohio through more than 30 years of freezing winters, I've found that heavy clay soils and deep ground freezes make a compressed-air blowout non-negotiable over simple manual draining. Settling soils in areas like Hudson and Akron create dips in lateral lines where pooled water inevitably rests and bursts PVC or poly pipes if not cleared with active air pressure.

For any climate experiencing sustained sub-freezing temperatures, manual draining is only viable on perfectly sloped, uniform terrain with dedicated drain valves at every low point. We run an air compressor regulated between 50 and 60 PSI across every individual zone until each head produces only a fine mist.

The single step that has most consistently prevented cracked components is leaving the backflow preventer's internal ball valves and test cocks open at a 45-degree angle after the blowout. Trapped water inside the valve cavity around a fully closed or fully open ball will split the brass housing as soon as the first hard freeze hits.

I choose by freeze severity, system layout and whether gravity can empty every low point. Shutdown alone suits sites without pipe-freezing conditions; properly sloped systems with drain valves suit manual draining. Hard freezes, buried loops, check valves or uneven ground justify a professional blowout because they can trap water. My final check covers the backflow assembly and each zone's lowest point; retained water means I keep draining.

One of my blowout lessons learned has been about testing your system after. Test the system 24 hrs later to make sure that you have all of the water out of the lines before temps start to drop.

Also, I have found that by paying particular attention to the backflow preventer and by making sure it's drained and then wrapped cuts my fall freeze leak calls by about 60% in the following spring. The backflow is typically the first thing to go because it gets beat up first. Being exposed to the elements and residual water make it a prime candidate. Most Tech's overlook it.

Keep in mind not all blowouts are created equal. You can not winterize them all the same (procedure should follow the system design, rather than the forecast.) Simple shut off blowouts only work if your system was built correctly (slope away downhill to drains at the low points). You need to take special consideration for systems with PVC lines that cannot take more than about a 50 PSI blast. Polyethylene is much more flexible, so it can handle compressed air better.

My experience managing maintenance and renovations across hundreds of units in South Florida gives me direct insight into handling occasional cold snaps without major disruptions.

I base the choice on a property's specific layout and exposure patterns from prior seasons rather than general climate assumptions. For multi-unit sites with varied terrain, manual draining often suffices when lines can be accessed quickly during short freezes.

In one renovation project, we mapped each zone's termination points ahead of time and used that data to skip full blowouts on sheltered sections. This approach kept work efficient while protecting the investment.

The check that has consistently helped is confirming every timer and controller is fully powered down before any weather shift, as residual programming has led to unexpected activations in the past.

I'm Ameer Badshah, owner of Rim Country Plumbing Co. in Payson, Arizona. We handle winterizing for homes across the Rim Country region, and here's how I think about it:

Blowout vs. manual drain vs. shutoff comes down to three things: your frost line, your system design, and your risk tolerance.

A full blowout (compressed air through the lines) is the gold standard anywhere the ground freezes more than a few inches deep. It's the only method that clears water from low spots, valve boxes, and backflow preventers where gravity draining leaves pockets behind. If you're in USDA zone 6 or colder, I recommend a blowout every fall, no exceptions.

Manual draining works in milder climates (zones 7-8) where freezes are brief and shallow. Open every drain valve, remove the backflow preventer for indoor storage, and leave valves at 45 degrees so any trapped water has room to expand. It's cheaper but less thorough.

Simply shutting down (closing the main valve) is only safe if the system was designed with proper slope for self-draining AND you're in a climate where the frost line stays above your pipe depth. Most residential systems don't meet both conditions, so I rarely recommend shutoff alone.

The single step that prevents the most spring leaks: remove and store the backflow preventer indoors. It's the most expensive component, the most freeze-vulnerable, and the one homeowners forget. Every spring, the majority of "mystery leaks" I see trace back to a cracked backflow preventer that spent winter outside. Five minutes in October saves a $200+ replacement in April.

The decision comes down to two things: how hard your ground freezes, and what your pipe is made of.

In hard-freeze climates, a full blowout is the only reliable option. Rent or hire a compressor, keep pressure at 40 to 50 PSI for PVC pipe (up to 80 for flexible poly), and blow out each zone until only mist comes out. Never exceed the rating of your pipe and heads.

Manual draining works in milder climates where freezes are brief and shallow, but only if the system was installed with drain valves at every low point. Most older systems were not, which is why this method fails more often than people expect.

A simple shutdown (close the supply valve, set the controller to rain mode) is fine only in frost-free areas like coastal Southern California or South Florida.

The single step that has most consistently prevented spring leaks is not about the lines at all. It is the backflow preventer. That brass device above ground will crack if water freezes inside it. Open both test cocks to drain it, leave the shutoff handles at a 45-degree angle so trapped water can escape, and in hard-freeze areas remove it and store it indoors. An insulated cover helps but is no substitute for draining. Skipping the backflow preventer is the most expensive ten-minute mistake in winterization.