There is a reason we talk every year about the preparation of the warmer and colder weather as the seasons change. There are many things that can help maintain your home and its mechanical systems, and make energy efficiency better. There are others that we talk about just to avoid damage. If you live in a place has regularly has freezing temperatures, or even has the potential for freezing temperatures, ther are some preccaution you should take to avoid freezing pipes. Although we talked about this at the beginning of the season, I want to re-address this with some examples of problems. 

This is a common vacuum breaking backflow preventer feeding the irrigation line to a home. 

This one was covered by a fake rock. I am sure you have seen these, which cover the ugly of having pipes stick up in your front yard, however, they don't offer much insulation from temperature by themselves. Most of the time there is an easy to access shut off valve to turn off watger to this system for the winter, as you cannot water the plants and grass below freezing or with snow on the ground anyway. This one was left on and forgotten for the winter. Here are some pictures of what can happen to pipe when it freezes.

You can see the the pvc pipe is crack and broken cross and lengthwise. The ice expands inside the pipe as it freezes and can destroy the pipe. This is not only true of the pvc, but brass, cast, steel, copper, and really most types of pipe have a point where they will break under the expansion pressures of ice. Here is a picture of the same backflow valve where the brass shut off is.

You can see the side wall split right open. Ice can be very powerful as it slowly expands with great force. This might not have happened if the water hd been shut off to this system for the winter, but even if there was still a pipe break, it would not have destroyed all of the pipe that it dit in this case and there would have been no water after the shut off, so the expese to fix would have still been less. 

I would suggest that for pipes like these 

...you should wrap them in any number of pipe insulation types or even heat tape which plugs in and heats the pipe from freezing when it detects below freezing temperatures.

They also make insulated covers for set ups like this 

Due to the cold, you can put this type of insulated cover right over the insulation wrapped pipes. Then if desired you can finally add the fake rock over the cover, like this one...

This can obviously be pretty extreme on exterior pipes, but when it is very cold, pipes can freeze for the inside of the house as well. Be prepared ahead of the cold, and remember that a frozen pipe can be warmed slowly with a hair dryer to get it flowing again if you catch it before there is any damage done. Always know where your water sut off valves are located for just such an emergency. Hope this will keep some of you out there from having the same issues in the future.