Freezing Towers

I was driving down the highway with my wife on the way to our in-laws' house a short time back and we passed a water tower. It was a cold day, below freezing, and I wondered for the first time why water towers do not freeze in the winter. It sure seems like a problem of exposed pipes to me, and they always freeze in your house if they are exposed to the outside in the winter.

I had no idea what the answer to that question was, but Andrea wanted to know why we even have a need for water towers in the first place. I knew the answer to that question, the water tower supplies what is called "head pressure" to the system (that system being the pipes going out to all the houses). You have a pump that is continually pumping water up to the tower. This pump is rated for just over the maximum average daily rate of water going out of the tank. People use water in surges during the day, just as they do electricity. Electricity is obvious, when it gets dark and everyone turns their lights on, the need for electricity increases. I was told by a power plant engineer once that in the winter right before Christmas when the sun goes down the electrical demand peaks, and it's all due to people turning on their Christmas lights. When it's really hot out, at mid-day when the temperature is the highest, all the Air Conditioners are cranked on full blast and electricity demand skyrockets.

For water, it's similar. Everyone gets up and takes a shower, people run their dishwashers around the same time of day and cook in the kitchen around the same time in the evening. People bathe their children in the evening around the same time. So there are these two spikes of usage with relative minimums of usage around them. The pump that feeds the water tower just cranks along at it's relatively low rate, just a fraction of the peak demand rate. The tower fills through the night and in the middle of the day and flushes out by gravity during peak demand times. The other reason to use water towers is to get higher pressure in your water pipes. If you've ever dived underwater, you've seen how the pressure on your ears gets greater as you go farther underwater. This is pressure head. The water in your pipes is at the same pressure (less friction losses in the pipeline) that you would be if you were underwater by that amount. The water level in the water tower minus your elevation is how far underwater you would have to dive to have the equivalent pressure on you. If you didn't have water towers, and expected to use a pump to create the peak demand flow at the pressures we get out of our facets now, it would be enormous. We save money and energy by doing it this way.

That explains why we have water towers and the pressure they create, now, why do they not freeze in the winter.

The answer to that is that the water is turned over too often in the tower. In the winter, they run the towers at lower levels, and the water going into the tower will be at ground temperature (usually about 55°F). This warmer water keeps the water tower from freezing. There is not as much demand in the winter, as people are not watering their yards or fields and gardens. Apparently, the water in the tank will freeze on top, like a pond. They prevent this from being a problem by cycling the level up and down in the tank. However, this is not as critical any more, because in our area we rarely have extended cold spells any more. The temperature might stay below freezing for a week or two, but then it would get above freezing, helping the tank to clear whatever ice is trying to build up. Farther north, they put mixers in the tanks to turn the water over and prevent the surface from freezing. The other exposed part that you have to be concerned with is the pipes going up and down from the tank. These are usually insulated so they will retain their internal heat, but sometimes they are heat traced or the space they are in is heated, but this is rare.

When you think about it, there are so many other things that work without us thinking about it or understanding. We take for granted electricity generation and transmission, water purification and distribution, and sewage treatment without even thinking about it.

It's not just big utilities that the average person is completely ignorant about, it's most of the things around your house. Obviously, the range of expertise about technology varies greatly from person to person. There are people out there that could probably fix anything and everything in their house. There are people that would be a wiz at doing their own plumbing, but would never touch anything electrical. Then there are those people that don't know what to do when their toilet keeps running or couldn't change a light bulb if they had to. I do wonder about some homeowners. If you don't know how anything in your home works, should you really be owning a house? If you have an endless supply of money, it's not a big thing, you can hire people to do the things you don't understand. But if you have a huge pile of money, you must have something going on upstairs, so home ownership can't be that much of a mystery. The thing that I don't get is someone that has a simple job, not making much and is challenged by most things technical. How do you justify buying a house? That's when you rent an apartment.

The same can be said for feeding yourself. If there weren't any grocery stores, could you figure out how to grow your own food or hunt and kill game to survive? We are so comfortably entrenched in civilization that we rarely realize how vulnerable we would be without it. The sudden reversal of civilization and rise of chaos and disorder is a common theme in science fiction stories. It's as if we've built a combination of a glass house and an ivory tower. Our glass tower, if you will. Shattering like an ice sculpture under a sharp blow.