HKstroud - questions - is the best way to get the water out of the water closet to turn off the water at the valve and then flush it? Should you turn the water off at the main valve and then use compressed air to get the water out? I do not know where I would get the amount of compressed air I would need. It does sound nice to make sure our pipes don't freeze during this 4 day run of overnight lows in the mid to upper 20s. Nadine

Best way is to turn off water at main valve. Then open all faucets and flush all toilets. That includes outside faucets. That way the water will flow out of the lowest valve. If you live where pipes are subject to freezing, the main valve should be located such that it is not subject to freezing.
There is no way to blow water out a pipe unless there is some kind of valve that can be used to drain. If you have pipes in an unheated area that cannot be drained, the best thing to do would be to install heat tapes and pipe insulation.

Where are you located (generally). Do you have concerns about a specific part of your pipes? Have you had problems with pipes freezing before?

Nadine,
I just look back at your previous post. I see that you just had a problem and replaced a lot of pipe. I'm not sure if that pipe was in your house or the underground line to the house.
Please describe your home and plumbing system.