{"id":5192,"date":"2025-11-05T13:51:19","date_gmt":"2025-11-05T20:51:19","guid":{"rendered":"https:\/\/www.treasurevalleyrepairs.com\/blog\/?page_id=5192"},"modified":"2025-11-05T13:51:20","modified_gmt":"2025-11-05T20:51:20","slug":"understanding-freezing-temperatures-and-sprinkler-systems","status":"publish","type":"page","link":"https:\/\/www.treasurevalleyrepairs.com\/blog\/understanding-freezing-temperatures-and-sprinkler-systems\/","title":{"rendered":"Understanding Freezing Temperatures and Sprinkler Systems"},"content":{"rendered":"\n

When the weather forecast drops below freezing, it\u2019s easy to panic about your sprinkler system. But here\u2019s the thing \u2014 ambient temperature (the air temperature you see on your weather app) is not the same as ground temperature, and that difference makes all the difference in whether your system is safe.<\/p>\n\n\n\n

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Ambient vs. Ground Temperature<\/strong><\/h2>\n\n\n\n

Air temperature changes quickly \u2014 it can fall from 50\u00b0F to 25\u00b0F overnight. The ground, however, is stubborn. Soil is dense and full of moisture, which means it retains heat and cools much more slowly. Even when the air dips below freezing for a night or two, the ground several inches below the surface can stay well above 32\u00b0F.<\/p>\n\n\n\n

According to the National Weather Service and USDA soil temperature data, soil temperatures in southern Idaho at 8\u201312 inches rarely drop to freezing until mid-December or even January. In most years, the ground acts like a giant thermal blanket for your underground sprinkler lines.<\/p>\n\n\n\n

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Why Your Underground Lines Are Usually Safe<\/strong><\/h2>\n\n\n\n

Most sprinkler systems are buried 8 to 12 inches deep. At that depth, the soil temperature lags weeks behind air temperature. It takes several consecutive days of round-the-clock freezing \u2014 not just chilly nights \u2014 before frost penetrates deeply enough to reach those lines.<\/p>\n\n\n\n

The real risks early in the season come from above-ground components \u2014 backflow preventers, valves, pumps, and filters \u2014 which have direct exposure to cold air. These are the first parts to freeze when the thermometer takes a dive.<\/p>\n\n\n\n

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Protecting Above-Ground Irrigation Components<\/strong><\/h2>\n\n\n\n

Even though underground irrigation lines are well-insulated by the earth and rarely freeze until deep winter, above-ground components like backflow preventers, valves, filters, and pumps are highly vulnerable once temperatures drop into the 20s. Fortunately, these can all be drained and winterized quickly and safely while you wait for your full sprinkler blowout.<\/p>\n\n\n\n

Backflow Preventers<\/strong><\/h3>\n\n\n\n

Before opening any test cocks, it\u2019s important to turn off the main irrigation shut-off valve and open the drain. These two valves are usually located in separate 4-inch valve tubes with caps, or sometimes together in a 10-inch round valve box near the backflow assembly \u2014 not inside the water-meter box.<\/p>\n\n\n\n

Once the main line is closed and the drain is open, you can safely drain the backflow itself. Use a flat-head screwdriver to turn each test-cock screw to a 45-degree open position, allowing air in and water out. Then turn both shut-off-valve handles at similar 45-degree angles. This vents any remaining water trapped inside and prevents the brass body from cracking when temperatures dip below freezing.<\/p>\n\n\n\n

\u26a0\ufe0f Never leave your main water supply on while your shut-off valves are closed.<\/strong> This can trap pressurized water inside the backflow and cause it to freeze and split.<\/p>\n\n\n\n

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Pumps<\/strong><\/h3>\n\n\n\n

Turn off power at the breaker or nearby switch, then remove the small drain nut at the bottom of the pump with a wrench. Open a hose bib or plug above the pump to release vacuum pressure and allow all water to drain completely. Replace the nut after draining so the system can be properly blown out later.<\/p>\n\n\n\n

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Filters<\/strong><\/h3>\n\n\n\n

Unscrew the bottom cap of the irrigation filter and let the water drain completely. If the filter is in a valve box and sits at an angle that prevents full draining, leave the cap off to allow expansion in freezing conditions. For exposed filters, draining is especially critical to avoid cracking.<\/p>\n\n\n\n

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Valves<\/strong><\/h3>\n\n\n\n

If your system hasn\u2019t been blown out yet, you can relieve pressure by turning the small manual bleed screws on each valve counterclockwise (do not remove them). You can also twist the solenoid slightly counterclockwise to let trapped air or water escape.<\/p>\n\n\n\n

\u26a0\ufe0f Make sure the main irrigation water supply is shut off first<\/strong>, or you\u2019ll give your yard an unexpected watering \u2014 and yourself a cold shower. Happens more often than you\u2019d think.<\/p>\n\n\n\n

In extreme cold (low 20s and below), add insulation or a towel over the valve box for extra protection.<\/p>\n\n\n\n

These simple steps can save hundreds of dollars in repair costs and buy you peace of mind until your system is fully winterized.<\/p>\n\n\n\n

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When to Take Action<\/strong><\/h2>\n\n\n\n

While there\u2019s no need to panic at the first frosty morning, it\u2019s smart to:<\/p>\n\n\n\n