How Long Does it Take for Pipes to Freeze? How do you thaw frozen pipes? At what temperature do pipes freeze? And more…We answer all of your questions about frozen pipes to help you prevent a disaster and get you through another winter.
Winter presents us with a whole lot of challenges. Not least of which are frozen pipes. When pipes freeze, they will often burst. This leaves the homeowner with a nasty mess to clean up and an unwanted repair bill. Ideally, we want to prevent our pipes from freezing in the dead cold of winter. If you’re looking for tips on preventing frozen pipes, this article is exactly what you’re looking for. How long does it take for pipes freeze? At what temperature do pipes freeze? Right now it may seem like all you have is questions and few answers.
By the end of this article, you should be fully informed. I intend answering all the frequently asked questions about frozen pipes and provide a host of handy tips on how to manage the cold and prevent your pipes from freezing.
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How Long Does it Take for Pipes to Freeze?
There is no definitive time period that it takes for pipes to freeze. The ambient temperature plays a role. This is obvious. In extremely cold weather, it won’t take too long before your pipes freeze. Insulation, and where your pipes are situated, is probably the most important factor in determining how long it takes for pipes to freeze.
In Northern climates, where the temperature is regularly expected to drop below freezing, building methods are implemented to prevent pipes from freezing. In the south, freezing weather is less common and many houses in these warmer climates are not built in anticipation of very cold weather. So houses in the South are usually more vulnerable, simply because the insulation and plumbing installations are not intended to withstand these extreme weather conditions. Though, even in the south, a freak cold snap could result in frozen pipes.
We all know that water freezes at 32° Fahrenheit. But will pipes actually freeze when the temperature reaches 32°? No they won’t. Pipes freeze when heat is transferred from the water inside the pipe to the surrounding air. This means that the surrounding air temperature has to fall well below 32° for the pipes to freeze. As a general rule, the temperature threshold where the likelihood of pipe freezing becomes a danger is 20°F. But this is a very basic estimation, based on uninsulated pipes in an attic without heating. While this may be applicable to Southern homes where insulation is not a great priority, it doesn’t apply to northern homes where more attention is paid to insulation against the cold. More importantly, it doesn’t tell us how long it takes for the pipes to freeze.
To obtain a more scientific explanation to this conundrum, I’ll refer to a study conducted by the University of Illinois (School of Architecture) in 1994 and 1995. This is a long and comprehensive document (View or Download Study), covering two phases of research. The first phase was laboratory testing under controlled conditions, using various types of common household pipes. They measured the external temperature and the pipe temperature. They then charted how long it took for the pipes to freeze at different temperatures. In the second phase, they conducted field tests in the attics of actual homes during the first three months of 1995. The results of the lab tests are the most interesting as they give us accurate data depicting how long it takes for pipes to freeze at certain temperatures.
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Using ½” copper pipe with ½” fiberglass insulation, at an ambient temperature of 20°F, it took about 2-hours for the pipe to reach 32°. This is the point at which the water in the pipe begins to freeze. For the pipes to become completely frozen to such an extent that there is zero water flow takes quite a bit longer. Freezing temperature seems to level out at about 3-hours. What I’ve managed to conclude from this is that, with little insulation, it’s going to take about 3-6 hours for your pipes to freeze when the air temperature is 20°F. The field tests also concluded that 20°F is the point at which pipe freezing is most likely to occur. This point of view was substantiated by 71 independent plumbing contractors.
In conclusion, I’ll summarize by saying that your pipes will not freeze when the air temperature reaches 32°F. You only need to be concerned when the weatherman forecasts temperatures of 20°F or less. Then it’s matter of how well your pipes are insulated and if they run through a heated area or not. With a reasonable amount of insulation, even pipes in an unheated area could take up to 6-hours to freeze. This means that the air temperature has to remain at 20° for about 6-hours before there’s a risk of your pipes freezing. On the other hand, if you have little or no insulation, your pipes could freeze in as little as 3-hours.
There is one more factor to take into consideration when determining how long it takes for pipes to freeze. Cold air moving across your pipes will cause them to freeze more rapidly. Pipes that are exposed to cold winds are at the greatest risk. If you have external pipes, pipes in a drafty attic, or have gaps in the walls of your home, your pipes may begin to freeze when the ambient temperature is above 20°F. If we take the wind chill factor into account, pipes that are exposed to the elements can begin freeze anywhere between 25° and 30° Fahrenheit ambient temperature.
How to Prevent Pipes from Freezing
It’s clear from the University of Illinois research that the time it takes for pipes to freeze can be as little as 3-hours. The key factor here is how exposed your pipes are to the elements. So the most important preventative measure is insulating your pipes.
Homes with pipes on the exterior walls and pipes in unheated attics are most at risk. These pipes will take the least amount of time to freeze. You may consider getting a plumber to re-route pipes that are not installed along well-insulated inside walls. Alternatively, you could install additional insulation around these pipes. Foam insulation will greatly reduce the risk of frozen pipes and is not expensive or difficult to do. Gaps in your walls are going to allow cold air into the crevices where your pipes run. So insulating your walls is also important.
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If you don’t want to spend money on insulating your pipes, there ways to do this. You could wrap old newspaper or rags around your external pipes. Though this is not the most effective prevention and these materials won’t last very long. If you live in an area where freezing temperatures are not too common, this could be a very cost-effective temporary measure. If you know unusually cold weather is eminent, you could use paper of rags to protect your pipes for this short period of time.
To do it right, you need to either use proper pipe insulation and install it correctly, like the Frost King Foil Backed Fiberglass Pipe Wrap OR foam pipe insulation — But in all honesty, a far better (and more expensive) solution is to use a heating cable like the Easy Heat, electric heating cable (from 3 ft. to 80 ft.).
Flowing water is not going to freeze as easily, if at all and there is now water pressure to cause a burst pipe. If you are any doubt as to whether your pipes have adequate insulation, you can leave a faucet open. You only need to leave the water running at a slow trickle. Even then, I’m not particularly fond of wastage and leaving your water running for a long time is an out and waste. Correct insulation is the best way to prevent your pipes from freezing.
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If you’re going to be away from home for any length of time during the winter, you may think that turning your heating off will save you some money. This could very likely turn out to be the opposite. The damage resulting from freezing pipes costs Americans $4.4 million annually. Not only do you have to pay for pipe repairs, but the resultant water damage to your home and its contents can be far greater than the actual plumbing repair.
Leaving the heat on while you are away from home in the winter may cost a little, but this is going to be far less than repairing the damage that results from frozen pipes. You don’t need to leave your heating set a normal comfortable temperature as you would when you were home. You can turn the thermostat down so that it’s just enough to prevent the air in your home from dropping to a point where your pipes freeze.
If the thought of unnecessarily leaving your heating furnace on when you’re not home doesn’t appeal to you, you can prevent your pipes from freezing without using heat. Before you leave, you can drain the water from your pipes by shutting off the main water supply and leaving all your faucets open. Leaving no water in the pipes, means there’s nothing to freeze.
Thawing Frozen Pipes
Prevention is obviously better than cure. But what if you the pipes in your home or the underground pipe leading to your home are frozen? How do you thaw these pipes? The obvious solution is to heat the pipes, this will melt the ice in your pipes and restore the water flow. Though you need to be careful, an open flame can damage your pipes, the walls and infrastructure around the pipes, or even cause a house fire.
To thaw the pipes in and around your home, a hair dryer is the safest way. If you can easily access the pipe, your quickest solution is to blow hot air along the pipe until the ice melts. If you can’t see the pipe, you can blow the hot air into an open faucet. This is going to take longer and you need to take care that when the water begins to flow, you don’t let it come into contact with the hair dryer.
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Thawing pipes in your home is relatively easy, but how do you thaw underground pipes? You may want to call a plumber to thaw your underground pipes. There is electrical equipment to heat the frozen pipe, but this can be dangerous and has to be performed by a qualified professional. In freezing weather, it may take a day or more before a plumber can find the time to attend to your problem. It’s likely that they have to attend to many homes before getting to you. There is a way to successfully thaw your underground pipes yourself.
You’ll need flexible hose with a diameter that will fit into the main water supply pipe. Since your water supply pipe is generally ¾”, a ¼” hose will easily do the trick. You’ll need a decent length hose as the blockage could be anywhere between your home and the street. If you’re able to run the hose from the point where the pipe enters your home to your street, it will definitely be long enough. You’ll also need a large storage bin, capable of holding at least 5-gallons of water, and a submersible pump (the kind of pump used for a garden pond).
You’ll need to gain access to the underground pipe. This would mean disconnecting the main supply pipe where it enters your home. Before you start, make sure that you have some way of shutting the water off when the blockage is removed. Once you remove the ice blockage, you’ll have pressurized water gushing through the opening in the pipe. The best way to do this is to fit a stop valve to the pipe opening.
Fill your bin to about ¾ from full and place your pump inside with your flexible hose connected to the pump outlet. Then you’ll feed the hose into your underground pipe. You may have to push and pull the hose back and forth as you work. Keep pushing until you hit an obstacle. This will be the point where the ice is blocking your underground pipe. Now switch your pump on and keep pushing back and forth on your hose with strokes of about 3 – 5 inches.
It may take some time, possibly a few hours, but the water will gradually melt the ice and remove the frozen blockage. You may think that using warm water will speed the process up, but it won’t really. Warm water will quickly cool and you’ll actually be wasting more time constantly replacing it fresh warm water. Water at normal temperature does a good job of melting ice – you just need to look at how quickly an ice cube melts in a glass of water. When the ice has melted and the water begins to flow, shut it off at the street. Remove the temporary shutoff valve and reconnect the main water supply to your home.
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