When you are going to be away from home for an extended time during the winter be careful about how much you lower the heat. That strategy makes a lot of sense in terms of energy savings but can be disastrous if a cold spell causes a pipe that would normally be protected freezes and bursts.
If turning off the heat is your preference, then the best way to protect the pipes is to drain the water system. With no water in the system, freezing is not a problem. Itís always a good idea to create a checklist when draining the water system, to be sure that no step is forgotten.Tools Needed
The first thing to drain in the hot water system is the water heater itself. You must turn it off before draining it. If it's an electric water heater, you will need to flip the water heater breaker in the power panel. If it's a gas water heater, there should be a "pilot" temperature setting on the heater. Failing to turn the water heater off before draining it will cause it to fail.
Inside your house, open the hot-water faucet in a sink or tub. This will prevent a vacuum from forming in the lines and preventing the heater from draining. Go back to the water-heater, attatch a garden hose to the water heater drain valve, and open the drain valve to drain the hot water out of the tank. Make sure the far end of the hose is draining somewhere that won't be harmed by hot water. A driveway is ideal. Finally, open all faucets. This will drain the water out of the pipes to the level of the lowest fixture.
With the hot water system drained, move on to the cold water supply. If the shut-off valve inside the house is a drain cock, the system is easily drained. Open all the faucets and let them drain until the water stops flowing.
Remember that water in a perfectly horizontal pipe will not completely drain, nor will water flow uphill without pressure behind it or suction in front of it. So to drain the system completely dry you will have to disconnect a section of pipe and force water out of the line with air pressure on both hot and cold water lines. If you have a summer house and need to completely drain the system for winter itís a good idea to install a utility faucet at the lowest level to allow water to drain without having to take pipes apart. Youíll have to use buckets or a hose depending on how the system is designed.
Credits and Suggested Reading:
University of Illinois, Building Research Council: An Investigation into Freezing and Bursting Water Pipes in Residential Construction Crawl Spaces in the Home