Will Empty Pipes Freeze?

Most recent answer: 02/18/2015

If I turn water meter off and drain my water lines in the house will the pipes still freeze when it is below 0 degrees?
- sand (age 50)
bell kentucky

Physicsist's answer: no. If the pipe is completely empty, there will be no water to freeze. The water vapour in air will not be able to condense on it either, because your house's walls (and pipes) will be slightly warmer than the ambient temperature on a typical day. Engineer's answer: yes. Unless you devise a way of draining all of the water proactively, say by sucking using a pump, there will be some remaining water in the pipes which may freeze. There are be two physical reasons behind this. Firstly, some parts of the pipes are lower than the level of the lowest tap. Due to the gravitational potential energy barrier, some water is trapped inside. There is almost always some water left inside the taps because of its internal architchture -whether at on or off position. Secondly, the bodies start to freeze outside-in, rather than inside-out. So I predict that the end portions of the trapped water (taps) will freeze before the rest. This means that the inner portion will again be tightly confined when it tries to expand during freezing, so may still lead to pipe faults. Leaving the taps half open partially alleviates the problem (from personal experience only).


(published on 02/18/2015)