Chances are, it's happened to you. An unexpected period of cold weather occurs and temperatures drop well below freezing for an extended period of time. One morning you attempt to turn the water on in the kitchen sink and...nothing. Hot water? Nope. Cold water? Nope. What happened? Did you forget to pay the water bill...again? Chances are, your pipes are frozen. "How can that happen? They are inside the house!", you may say; however, just because your water lines are inside the building envelope, does not mean they are adequately protected from freezing.
Most modern plumbing codes not only require water lines to be located in areas protected from extremely cold temperatures, but also require additional measures to be employed to directly protect them from freezing. For example, the Indiana Plumbing Code 675 IAC 16-1.3, Section 313.6 states: "No water, soil, or waist pipe shall be installed or permitted outside of a building or in an exterior wall unless provision is made to protect such pipe from freezing." What exactly does that mean? How do you directly protect your pipes? When should you worry about your pipes freezing? In 2006, a study was conducted by the Building Research Council (BRC) at the University of Illinois in an attempt to answer those questions.
When should A Homeowner Be Concerned?
When should homeowners be alert to the danger of freezing pipes? That depends on several factors, but in general, for water lines inside the building envelope, the temperature alert threshold is 20°F. Though water freezes at 32°F, the exterior walls of a building (assuming they have no openings to the outside), provide some protection for the pipes and slow heat loss. According to data collected from field tests conducted by the BRC, un-insulated pipes installed in an unconditioned attic and subjected to winter temperatures began to freeze when the outside temperature fell to 20°F or below. Several plumbers practicing in southern states were also surveyed on the matter and the consensus was that pipes began to burst when temperatures fell into the teens. It should be noted, however, that freezing incidents can occur when the temperature remains above 20° F. Pipes exposed to cold air entering the building through cracks in an outside wall or pipes that lack proper insulation are vulnerable to freezing at temperatures above the threshold.
So we ask again, what are homeowners to do to prevent their pipes from freezing? The three primary ways of protecting your pipes from freezing in cold weather are locating them properly, adding insulation, and mechanically heating them. There are also smaller, proactive measures one can take to help ensure the integrity of their water lines.
Depending on the age of the house, the location of the pipes is the aspect a homeowner has the least control over. In new construction, proper placement can be designed into the building; however, in existing houses, a plumber may have to re-locate exposed pipes, though this is generally not a practical solution. Houses in northern climates are constructed with the water pipes located on the inside of the building insulation, which protects the pipes from extremely cold temperatures. Water pipes in houses in southern climates often are more vulnerable to winter cold spells, as the pipes are sometimes located in unprotected areas outside of the building insulation.
Insulation around the pipes is passive protection and is most effective if water in the pipes is flowing frequently during periods of freezing temperatures. The insulation slows the heat loss from the pipe, but if temperatures are cold enough and if the water remains stagnant in the pipes for an extended time, then the water will freeze.
Insulation can take various forms, including foam sleeves and pipe "tape", which are wrapped around the pipe; or batt insulation, which is used to block the flow of cold air from the outside. In some instances, expanding foam can be used to achieve both goals. This can be used in instances when the pipes are not easily accessible, as the spray can allows you to place the foam into wall cavities and crevices through a relatively small opening.
Water lines can also be heated directly by mechanical means. The use of space heaters in areas that have exposed water lines can regulate the temperature and prevent freezing. Electric heating tapes and cables are also available to run along pipes to keep the water from freezing; however, these must be used with extreme caution to avoid the risk of fire. Tapes and cables with a built-in thermostat will turn heat on when needed, though tapes without a thermostat have to be plugged in each time heat is needed and may be forgotten.
Homeowners can be proactive in protecting their water lines by preventing cold air from entering the building or by ensuring exposure to warm air from the interior of the building. Pipes in attics, crawl spaces and outside walls are all vulnerable to freezing, especially if there are cracks or openings that allow cold, outside air to flow across the pipes. Holes in an outside wall where television, cable or telephone lines enter can provide access for cold air to reach pipes should be sealed to prevent cold air from reaching the pipes. Keep kitchen and bathroom cabinet doors open during severely cold weather to let warm air circulate around the pipes.
Relieving Pressure on Water Lines
Letting a faucet drip during extreme cold weather can prevent a pipe from bursting, though it is not a guarantee. Moving water loses heat to the surrounding environment more slowly due to "new", relatively warmer water constantly replacing the cooler water. It should be noted, however, that the colder the outside air, the more water that will need to flow past a certain point over a given period of time. Elbows in pipes reduce water velocity, making such areas more susceptible to freezing. Also, opening a faucet will provide relief from the excessive pressure that builds between the faucet and the ice blockage when freezing occurs. A dripping faucet wastes some water, so only pipes vulnerable to freezing (ones that run through an unheated or unprotected space) should be left with the water flowing. Where both hot and cold lines serve a spigot, make sure each one contributes to the drip, since both are subjected to freezing. If the dripping stops, leave the faucet(s) open to provide pressure relief.
1. Gordon, J.R., "An Investigation into Freezing and Bursting Water Pipes in Residential Construction" Research report 96-1, Building Research Council, School of Architecture, University of Illinois at Urbana-Champaign (2006)
2. Weather.com - Preventing Frozen Pipes (http://www.weather.com/activities/homeandgarden/home/hometips/severeweather/pipefreeze_prevent.html)
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