Can a Water Service Line Freeze?

Another icy blast of winter weather has come through, and there's no water to shower. You know water lines can freeze, and you wonder how you're going to thaw the pipes without causing water damage. You promise yourself you'll winterize them for next year.

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Can Water Service Lines Freeze?

Yes, water service lines can and do freeze, even during a mild winter. All that's needed for a frozen water line is a spell of icy weather when temperatures plummet. At temperatures below 20 degrees Fahrenheit (-7 degrees Celsius), it takes less than six hours for your plumbing to freeze. Frozen pipes are a major concern because water expands as it freezes, putting stress on rigid water lines. Water service lines vulnerable to freezing include:

• Underground water service lines. These lines may freeze if they aren't buried below the frost line or insulated against cold temperatures.

• Water lines in buildings. Pipes in unheated parts of the home, such as basements, crawl spaces and attics, are especially vulnerable.

• Exposed water lines. All outdoor and exposed water lines can freeze once the air temperature drops below 32 degrees Fahrenheit (0 degrees Celsius).

How Deep Are Water Service Lines Buried?

To prevent freezing, contractors bury water lines below the frost line for your area. The frost line, or more strictly speaking, the frost depth, is the distance below ground that frost penetrates during a typical winter.

Frost Line Depth

The frost depth line varies across the United States, from 0 inches in Florida to 100 inches in parts of Minnesota. In Canada, it varies from 18 inches in coastal areas to 144 inches in parts of Manitoba. The actual frost line changes from season to season and may be deeper during colder winters.

Practical Considerations When Laying Water Service Lines

With such a wide variation in depth, it can be difficult to lay water pipes so they're below the frost line. Plus, there may be existing natural and man-made barriers to contend with, such as large tree roots, stormwater drains or gas lines. To help avoid frozen lines, use flexible PEX piping (cross-linked polyethylene), add underground insulation and backfill trenches with sand. Always follow local codes when laying water lines.

What Happens If a Water Service Line Freezes?

When a water service line freezes, the water in the pipe expands about 9%. This expansion exerts enormous pressure on the pipe and, depending on its construction, it may split or burst. The first sign of a frozen pipe may be no water coming from a faucet, although if the pipe hasn't fully frozen, you may still get a trickle. Worse, you may not know you have a burst pipe until the ice melts, and unless you're prepared for it, the leak could cause localized flooding in your home.

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Can You Prevent a Water Service Line From Freezing?

Water line freezing prevention is possible. Consider which pipes are most likely to freeze. These can include water pipes laid at a shallow depth in the ground and surface pipes situated in uninsulated walls, floors, unheated garages, attics or basements. Ways to stop pipes from freezing include:

• Insulate pipes. Fit pipe insulation around accessible water service pipes, especially if they're copper.

• Install heat trace cable. Insulation isn't always effective when water service pipes are shallow, exposed or in the frost zone. In these instances, wrap the pipes with electric heat trace cable.

• Keep indoor pipes warm. Add insulation to exterior walls, floors and the attic. Keep the kitchen and bathroom heat on, and open cabinet doors to let warm air reach the pipes.

• Use the drip technique. A small amount of water flowing continually through vulnerable pipes can help keep them from freezing, so allow your faucets to drip. Flowing water can also break up ice already formed inside pipes.

• Add frost-proof fittings. Install frost-resistant fittings on pipes likely to freeze, particularly outdoor faucets. Install PEX lines on outdoor spigots, as this material expands to accommodate forming ice.

• Drain seldom-used pipes. Drain irrigation pipes, water lines in unheated areas such as a garage and outdoor spigots to limit potential damage from freezing.

How to Thaw a Frozen Underground Water Line

Thawing pipes is difficult and should be done carefully. Apply gentle heat to the frozen section of pipe using a space heater, blow-dryer or heating pad. Leave the faucet open to relieve pressure as the ice melts. Never use a blowtorch or open flame, as this could melt the pipe. Use caution, because applying too much heat could turn melting ice into steam, increasing the risk of a burst pipe. If necessary, call in a professional to thaw your pipes.