The weather situation in Texas has been a terrible disaster. Cold temperatures, along with the loss of power, mean that many people have been stuck inside their homes with no heat. On top of that, most of the houses and buildings in Texas are not designed for extended periods of below-freezing temperatures. This means that there have also been many frozen and busted water pipes. Not good.
But everyone tries to make things work with what they have. You may have seen this photo making the rounds on Twitter, which data and social scientist Rumman Chowdhury snapped outside a fast food restaurant in the Houston suburbs, where some clever person had apparently attempted using a bunch of hamburger buns to insulate a pipe.
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We called the manager of this particular establishment, who said they knew nothing about it. So without any intel, we wondered: Would this actually work? Why do water pipes burst in cold weather anyway? Let's get to it.
Freezing Water Is Weird
We live in a world of water (H2O). There's water as a gas (water vapor), as a liquid (that wet stuff), and as a solid (ice). But water is weird. It does something that most other substances don't do—its density as a liquid is greater than its density as a solid.
But it's not just that water floats when it becomes ice; it expands when it freezes. It has to expand. If you have 1 gram of liquid water that turns into 1 gram of ice with a lower density, it has to take up more volume. This expansion of liquid water as it becomes ice is so powerful that it can break out of a container. You've probably seen this if you’ve accidentally left a full bottle of water in your freezer, but it can also break metals like steel.
Here is an older physics demo that I found in a lab. It's called an ice bomb—not because it's made of ice, but because ice makes it explode. Check it out.
This is a small steel container with a screw nut on the top. You fill it with water (leaving no air gap) and then freeze it. When the liquid water inside turns to ice, the pressure is great enough to break the steel container. I always think about how awesome this is because you make something explode by removing thermal energy instead of adding it.
So, imagine this steel container is instead the water line going into your house. (Unless you collect rainwater or make water from hydrogen and oxygen, you probably have one.) If it gets too cold, the water can freeze and literally burst your pipe. That's bad. Now for some questions and answers.
Why Doesn’t This Happen More Often in the South?
Residential water lines are almost always underground—and that's a good thing. Although air temperatures can vary drastically from summer to winter, the ground temperature is much more constant. In the southern states, this ground temperature isn't very likely to get below freezing—so water in the pipes will also be above freezing (and stay liquid).
But there are some exceptions. In some places with warm climates, not all parts of a water pipe system will be underground, and will pass through regions of air. (Heck, I have water pipes in my attic, and I live in a warmer location). Although there is a small temperature difference between cold water (let's say 1 degree Celsius) and warm ice (0 C), there is a huge energy difference. It takes quite a bit of energy to change water from its solid phase to a liquid. We call this the latent heat of fusion. For water, this has a value of 344 joules per gram. That might be difficult to comprehend, so how about an example?
Suppose you have a liter of ice (with a mass of about 1,000 grams). If you want to take this ice at 0 C and turn it into water at 1 C, it would take 344,000 joules of energy (plus a tiny bit more energy to raise the temperature of water). How much energy is that? Well, let's say you have a smartphone with a 3,000-mAh battery (milliamp-hours). This is equivalent to 41,000 joules. So, it might have enough energy to run your phone for a full day, but you would need eight or nine of these phones to melt all that ice.
It's actually a good thing. It means that you can use melting ice to cool off your drinks—and you don't actually need that much ice. That also means that you need to remove quite a bit of thermal energy from your pipes to get them to freeze. One cold night probably isn't going to be enough to make your pipes burst.
Does It Help to Leave a Faucet Running?
Yes. OK, imagine you’re inside of a water pipe. (Yes, you are super tiny now.) If the water is stationary, you might be stuck in a part of the pipe that is exposed to cold air. You could actually freeze, and then you would have to break the pipe. But now suppose it's running water, caused by a faucet that is slightly dripping. You are still a tiny person inside of a pipe, but now you are also moving. You pass through the section of cold pipe and you get cold—but you don't freeze. Instead, you just move on to other parts of the house.
Oh, but more water from the main underground line is coming into that cold part of the pipe. Would it freeze? It's not as likely. Remember, the water pipe is at ground temperature, which is almost certainly not below freezing. So, the incoming water isn't super cold, and hopefully it won't freeze.
What About Insulation?
Insulation helps. If you wrap some foam insulation around any exposed pipes, it does the same thing as your cooler or insulated drink cup. The insulation decreases the rate that energy is transferred from the hot thing to the cold thing through a thermal interaction. If you put a cold drink out on a table, energy is transferred into the drink to cause it to increase in temperature. Putting the drink in a cooler, on the other hand, increases the insulation and decreases the rate of energy transfer so that it takes longer for the drink to warm up.
For the foam insulation around a pipe, the water is warmer than the air, so this decreases the rate of energy transferred out of the water. Remember, if you remove enough thermal energy from the water, it will make a phase transition from a liquid to a solid—and that's the bad part. So, yes—insulate those pipes.
Can You Use Hamburger Buns As Insulation?
Now we are getting serious. This is the answer you are looking for—and I'm going to give it to you. I think the answer is yes. Yes, putting hamburger buns around an exposed water pipe will increase the insulation and reduce the chance of having a frozen (and burst) pipe.
But how would that work? Well, one of the absolute best insulators is air. It's not as good as nothing (a vacuum), but it's still pretty effective—and much easier to make than a vacuum insulator. In fact, that's the idea behind most insulators: Get some air. You know what makes rubber foam such a nice insulator? Yup, air. The foam has tiny air spaces inside of it. What about that nice fleece jacket? It's air. The fleece traps air and that makes it a good insulator. Even the fiberglass insulation in your walls and attic really just traps air to insulate your house.
What about a hamburger bun? I don't know if you've ever looked at a bun closely, but if you do you will see air. I mean, bread seems like it's mostly air—those little bubbles inside the dough make it expand when you bake it. So, I would guess that these buns would work as a pipe insulator. It definitely wouldn't make it worse, so it's worth a shot. Losing a bunch of buns is probably cheaper than fixing a broken water pipe.