How to Keep Pipes from Freezing

Every winter those of us that live in a region likely to have either phases of freezing weather or prolonged freezes face the problem of how to keep the plumbing pipes in our house from freezing and bursting. A frozen pipe can mean costly repair and cleanup bills plus several days without water in part or all of the house. Unfortunately, many of us tend to respond to the threat when the crisis is upon us rather than when the weather is nice and the chore of weatherizing the house is not so unpleasant.

Regional Pipe Freeze Risk Factors

Contrary to logic it is usually the homes in more temperate climates that run the risk of pipes freezing in winter. Because of the constant risk of freezing, homes in northern climates are usually built with the water pipes on the inside of building insulation which protects them from subfreezing winter temperatures. In southern climates where winters are usually shorter and more temperate, the pipes are more often located in unprotected areas and home owners tend to be less aware of freezing problems which may occur only once or twice a year and not last more than a day or two.

Newer construction (and construction in an area where subfreezing temperatures are typical for an extended period) is likely to be designed with pipes located in protected areas or with insulation around the pipes. But older home in the south may not be designed with these safeguards.

Why Pipes Freeze

Counter- intuitively, pipe bursts do not usually occur at the site of the ice blockage. The break will usually occur downstream from the frozen area. Following a complete ice blockage in a pipe, freezing and expansion inside the pipe causes water pressure to build between the ice and a closed faucet at the end. So the breakage will usually be somewhere between the ice blockage and faucet. Usually the pipe will burst where little or no ice has formed. Upstream of the ice blockage (between the ice blockage and where the water enters the system from its source) water can always retreat back towards the source so there is not likely to be enough pressure build up to cause pipes to break in that area.

When is it Cold Enough for Pipes to Freeze?

In southern states and other areas where freezing is not typical and where pipes are not adequately protected by the building insulation or structure, the temperature threshold alert is usually 20oF.

This threshold is based on research conducted by the Building Research Council at the University of Illinois. This finding was supported by a survey of 71 plumbers in southern states who concurred that burst-pipe problems began to appear when temperatures fell into the teens.

However, pipes exposed to cold, flowing air (such as pipes in a drafty crawlspace, a basement with cracks in an outside wall, or an attic space exposed to air flow) may be vulnerable to freezing at higher temperatures.

So a night that dips to freezing or just below may not cause a frozen pipe, but a prolonged period of temperatures dipping into the teens is cause for concern.

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