Why Do Pipes Freeze?


For most people, winter brings plummeting temperatures. The chilly weather not only freezes water, but can also cause pipes to freeze. So why does this happen?

Why do pipes freeze? Pipes usually have a small amount of water in them, even if you have your taps turned off. This water can freeze on days when the outside temperature is at least 20 degrees Fahrenheit. If you live in an area that does not usually suffer from sub-zero temperatures, chances are your water pipes lack the proper insulation to protect them from extremities, which could cause them to freeze.

Wind chill also contributes to pipes freezing – if there are any unheated spaces such as cracks, holes, or openings for cold, outside air to blow in, the cooling effect can speed up ice formation in pipes. It’s worth noting that water expands as it freezes, exerting pressure on the pipe from the inside out. Whether the pipe can withstand this pressure without buckling will depend on the volume of frozen water, the shape, type, and age of the pipe, and whether corrosion was already present in the pipe.

Frozen pipes can leave your home without running water, plus they are at risk of bursting and flooding your home. Read on to discover why and how pipes freeze, how to thaw them if they do freeze, and how to keep them from freezing.

How does a pipe freeze?

As temperatures drop, water begins to freeze, and water pipes that are on the outside of your home are particularly susceptible to freezing. A frozen pipe can interfere with the flow of water into your home. On top of the inconvenience, frozen pipes are also at risk of rupturing, leading to serious leaks and even flooding.

Water expands when it freezes. As previously mentioned, even when your taps aren’t turned on, your pipes will usually have a small amount of water in them. If this water freezes, it expands, pressurizing the pipe from the inside out and putting the whole plumbing system at risk of rupture. That said, the pipe is unlikely to burst where ice forms – instead, freezing portions of the pipe exert pressure downstream between the faucet and the ice blockage. The pipe breaks where the pressure is the highest, usually in the places that don’t have any ice at all.

Wind chill can also contribute to freezing pipes. If there are unheated spaces in your home that allow cold, outside air to blow in (through holes, cracks, or openings for example), the cooling effect often speeds up the formation of ice in pipes. 

Your geographical location can also play a role in freezing pipes. Water systems that are in areas that usually don’t suffer from cold winter may be at higher risk of frozen or ruptured pipes. This is because, in warmer climates, homes aren’t usually designed with freezing temperatures in mind, and homeowners may not be familiar with winterizing techniques. When temperatures unexpectedly plummet, many warm-weather structures are unable to handle the extreme temperatures as they don’t have adequate insulation, leading to ice blockages, burst pipes, and flooded homes.

Pipes that are located in unheated spaces are especially vulnerable to ice blockage, including attics, basements, and garages. Even pipe systems that are found in exterior walls can freeze under the right conditions.

At what temperature does a pipe freeze?

The freezing temperature of water is 32 degrees Fahrenheit. However, this doesn’t necessarily mean that on days that it’s 32 degrees outside, your pipes will freeze.

Typically, your home’s pipes will begin to freeze when the outside temperature is about 20 degrees Fahrenheit. This temperature was determined by a research conducted at the Building Research Council at the University of Illinois. 

However, this is not a fixed rule. Depending on your geographical location as well as your pipes’ exposure to wind and the elements, they can freeze even when temperatures are higher than 20 degrees. 

How long does it take for pipes to freeze?

Pipes will freeze at temperatures of 20 degrees Fahrenheit and below, but just how long it takes depends on a couple of things:

  • Insulated pipes – For pipes that are well-insulated, you can expect your pipes to freeze after 6 hours of no use or heat.
  • Poorly insulated pipes – For pipes that have little or no insulation, the freezing risk becomes imminent after as little as 3 hours when in temperatures of 20 degrees and below, without use or access to a heating source. 

The average time it takes for a pipe to freeze and potentially burst in temperatures of 20 degrees and below without use or a heating source is about 4 to 5 hours.

How to thaw frozen pipes

Thawing a frozen water pipe in good time can help you avoid a burst pipe and potentially damaging flood. 

  • Locate the frozen pipe – To thaw a frozen pipe, you must first locate it. Turn on the faucets in your home. If there’s no water coming out, or the pressure is extremely low, then a pipe leading to the faucet is likely frozen. 

If the affected pipes are exposed, such as pipes under sinks, along the exterior of the house, or in basements, you may be able to pinpoint the portion of the pipe that is frozen. You may notice that it has frost on it or it has a slight bulge. 

  • Open the faucet – Before you begin the thawing process, open both the hot and cold handles of the faucet that the pipe feeds water into. This will help to relieve the pressure that has built up in the system and will allow the water to escape once you begin thawing the pipe. 
  • Work your way down to the ice blockage – You always want to begin the thawing process near the faucet then slowly work your way down to the blockage. This way, the melting ice and steam can escape through the open faucet. If you begin to thaw closer to the blockage, the melting ice could get stuck behind the blockage, subsequently creating more pressure in the pipe and increasing the likelihood of the pipe bursting. 
  • Thawing exposed pipes – If the frozen pipe is easily accessible, there are several options you can try to thaw the pipe:
  • Hair dryer – One of the easiest thawing pipes involves using a hairdryer. All you need to do is turn on the dryer, put it on the highest heat setting and point it at the pipe, starting at the portion closest to the faucet.
  • Heat lamp or portable space heater –  You can also try thawing your pipe using a heat lamp or portable space heater. Position your chosen device so that the heat it emanates can reach the frozen pipe. The indirect heat can help to thaw the pipe quickly. 
  • Electrical heating tape – Another option is to apply electrical heating tape directly to the pipe which will distribute heat throughout the pipe. 
  • Hot towels – Finally, you can try thawing frozen pipes by wrapping hot towels around the pipe. This can help to gradually thaw the blockage.
  • Thawing enclosed pipes – If the frozen pipe cannot be accessed, you can try the following options:
  • Turn the heat up in your property – You can attempt to thaw a frozen pipe by increasing the temperature in your property.
  • Infrared lamp – If you can pinpoint the location of the frozen pipe in the wall, you can attempt to thaw it by placing an infrared lamp in the front of the portion of the wall where it is. The heat may be able to penetrate through the wall and let the pipe to defrost.
  • Cut out a section of the drywall – If you don’t mind, you can cut out a section of the wall in front of the frozen pipe so that you can access the pipe, and then use one of the methods listed above. 

If a frozen water pipe ends up bursting, shut off the main water line immediately to prevent additional water from flowing and damaging your property. 

How to prevent frozen pipes

If cold weather is on the way, it’s worth taking some precautions to prevent frozen pipes:

  • Keep your heat on – If you’re not planning to be home during the winter, you’ll want to leave the heat on while you’re away. It may seem counterintuitive to turn your heat on for an empty space, but the heat can help to prevent pipes from freezing, potentially bursting, and causing a lot of water damage to your property and possessions.
  • Keep your water faucets running – It’s harder for running water to freeze, so you can open a faucet (or two) just a bit so that it drips slightly. If the faucet is connected to both hot and cold water pipes, open both taps slightly. This can help to relieve the pressure that may have built up in the system. 
  • Keep interior doors open – If you have pipes in your bathroom and kitchen cabinets,open these interior doors to allow heat to evenly and consistently spread out in the space. 
  • Seal up cracks and holes – You’ll want to seal cracks and holes where your pipes run through floors or walls to prevent cold, frosty air from coming in. You can use caulk or spray foam solution to fill these gaps.
  • Insulate pipes – Pipes in attics, basements, or any other areas that lack proper insulation may need extra insulation so that they don’t freeze. You can fit these pipes with fiberglass sleeves or foam rubber to keep them insulated.

Final thoughts

Frozen pipes are inevitable under certain conditions, so it’s always wise to take preventative measures to avoid having to deal with serious and expensive damage down the road. If you need help accessing your pipes, consider getting a professional to come in and do the work for you.

Melanie Asiba

Melanie is an author. She enjoys traveling, reading and trying out new things. In addition to writing for Apartment ABC. Connect with her at [email protected]

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