How to Thaw and Prevent Frozen Water Pipes

Broken water pipes
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Project Overview
  • Working Time: 1 - 2 hrs
  • Total Time: 1 - 2 hrs
  • Skill Level: Beginner
  • Estimated Cost: $5 to $10

Frozen water pipes are a serious risk during very cold winter weather. When water freezes in a pipe, it expands and can exert pressure at over 2,000 pounds per square inch. That's enough to rupture almost any pipe since there is no place for the ice to expand.

A ruptured pipe can be a time bomb. Initially, there may be no leaking at all since the frozen water can completely block the pipe—until the ice begins to thaw, at which point you are on the verge of a major flood. There are many instances where homeowners try to escape a cold winter for a few weeks of vacation in a warm climate, only to return to a home that has been devastated by tens of thousands of dollars in damage from water that has destroyed walls, ceilings, and floors. 

Pipes are most susceptible to freezing when they are located:

  • In an outside wall that is subject to freezing outdoor temperatures
  • In a cabinet under a sink (especially when located near an outside wall)
  • In an unheated crawl space or basement
  • Near outdoor faucets (hose bibs) used to connect garden hoses 

If your pipe is frozen but not yet ruptured, you must thaw it right away. There are a few thawing techniques to try, depending on where the frozen pipe is located.

Warning

Never use a blow torch or other open flame to thaw a pipe. This presents a serious fire hazard and can damage the pipe.

Locating the Frozen Water Pipe

A frozen pipe that hasn't burst yet often reveals itself at a faucet. When you turn on the faucet in very cold weather and no water comes out or has slowed to a trickle, there is a good chance the pipe is blocked with ice somewhere in the line.  It's time​ to take immediate action. 

Shut off the water to the faucet locally or at the home's main water shutoff valve.  Open the faucet that is supplied by the frozen pipe; do this even if you don't know where the blockage is.

Identify the frozen pipe and locate the blockage. Follow the pipe back from the faucet to where it runs through cold areas, such as an exterior wall or unheated crawl space. Look for areas of the pipe that have frost or ice; it may also be slightly bulged or fissured.

How you thaw the pipe will depend on where it is located. 

What You'll Need

Equipment / Tools

  • Infrared heat lamp
  • Hair dryer
  • Portable heater

Materials

  • Electric Heat Tape

Instructions

How to Thaw a Frozen Pipe Inside a Wall

When you find that a pipe that is frozen but not yet burst is located behind the surface of a wall or ceiling, you've got a challenge on your hands.

  1. Turn Up the Heat

    Turn up the heat in the house and wait. If you suspect the pipe is inside the wall within a bathroom or kitchen sink base cabinet or vanity, make sure to open the door of the cabinet to help the heat reach the wall. 

  2. Use an Infrared Lamp

    Use an infrared lamp to help heat the wall section where you believe the pipe is frozen. Infrared lamps are better than regular heat lamps because they radiate through the air without heating it and will direct more energy to warm the wall and frozen pipe. There is less chance that the infrared lamp will dangerously overheat the wall materials. 

  3. Open Up the Wall

    If you are very concerned that a burst pipe is imminent, cut out a section of the wall or ceiling to access the frozen section of pipe, then thaw the pipe as if it were an exposed pipe.

How to Thaw a Frozen Exposed Pipe

If the frozen pipe is exposed, such as may be present in an unfinished basement or garage, you have several options for thawing it. Whichever remedy you use, begin heating the pipe from the faucet side toward the frozen area. This allows water to flow out as the ice melts.

  1. Try a Hair Dryer

    This is usually the easiest and safest way to thaw a pipe. If the pipe is close to the wall, place a cookie sheet behind the pipe to help radiate heat onto the backside of the pipe.

  2. Use a Heat Lamp

    You can use an infrared or incandescent heat lamp. As with a hairdryer, if the pipe is close to the wall, use a cookie sheet behind the pipe to help reflect heat onto the pipe and protect any wall coverings behind it.

  3. Set Up a Portable Heater

    A small, powerful heater works great for warming pipes under a kitchen or vanity base cabinet. Direct the heater onto the frozen section of the pipe. Make sure to keep an eye on the heater as you are heating the pipe.

  4. Use Electric Heat Tape

    Heat tape is a ribbon-like wrap that contains electrical heating elements. Wrap it around the pipe you want to heat and plug it into the wall. The temperature of the tape is controlled with a thermostat. Heat tape can also be used to prevent pipes from freezing in critical areas. You can leave the heat tape on the pipe and plug it in only when needed.

Tips for Preventing Frozen Pipes

There are a few things you can do to prevent the problem of freezing pipes from occurring again:

  • Leave the faucet dripping during the coldest times. The steadily moving water will keep the pipes slightly above the freezing point and prevent them from freezing. No one wants to waste water, but it is better than dealing with burst pipes. A burst pipe can easily spill several hundred gallons of water per hour.
  • Open cabinet doors to allow the heated air from the room to reach pipes inside the cabinet. This is often sufficient to prevent kitchen pipes from freezing on the coldest nights.
  • Wrap the problem pipe with electrical heat tape and plug it in when the weather is especially cold. 
  • Insulate problem pipes with foam insulation wrap, especially those that run through unheated spaces. But remember that insulation merely slows the transfer of heat and will not prevent a pipe from freezing if the surrounding air is cold enough. ​
  • Install a permanent heater to keep areas with pipes above the freezing point. For example, an unheated basement or garage can be fitted with a permanent baseboard heater to keep temperatures above freezing. However, do not use portable heaters, which should never be left running unattended.
  • Remove garden hoses attached to outdoor faucets (hose bibs or sillcocks). If the faucet is not a frost-proof type, winterize the pipes by turning off the water to the faucet inside the house and draining the exterior section of the pipe and faucet.
Child turning off a tap
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Home thermostat
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Frozen plumbing
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Water faucet
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