https://home.howstuffworks.com/home-improvement/plumbing/dripping-faucet-prevent-frozen-pipes.htm
(ABOVE) More info: https://www.sciencefacts.net/why-does-water-expand-when-it-freezes.html
(ABOVE) This is a burst pipe that flooded several units because the unit owners were not home to run the water.
Water has a unique property in that it EXPANDS as it freezes. This expansion puts tremendous positive outward pressure on whatever is containing it, including metal or plastic pipes. No matter the strength of a container, expanding water can cause pipes to break.
Dripping faucets during weather below 32 degrees is an absolute MUST to create negative space in your plumbing. Then the water that is freezing can dynamically expand into the fluid negative space created by water running out of a faucet. When water freezes and expands in one place, without expansion space, it causes pipes to pop as shown on the 2nd photo.
SEVERAL OTHER HELPFUL SCIENTIFIC REALITIES:
- At McGill Place the water entry is near the hot water heater but the pipes most vulnerable to freezing are on the exterior walls. Thus running faucets nearest the outside walls is advantageous. But setting ANY faucet to drip will help. This relieves the fluid pressure in pipes that cause them to expand and explode when ice freezes.
- In a house with 4 walls to the outside weather, the dripping faucet should be as far away from the water source as possible so the water will flow through the entire length of the system to relieve pressure building up from ice expanding.
- If going away for a length of time in the winter a good idea would be to cut off your unit water at the unit cut off valve and drain the water from your system from the lowest point of gravity, for example the tub if this is the lowest point.
Q: I have a pipe stub that is not being used from a kitchen remodel that is located near an outside wall. Will this pipe freeze because water is not running through it?
A: A common misconception is that the drip prevents water from freezing because it stays in motion when it’s running through the pipes. Although this helps, the truth is that at extreme temperatures water can freeze and expand even while it is flowing!
The real reason a dripping faucet can help prevent pipes from bursting is that the constant drip relieves positive pressure that is building up in the pipes between the active ice formation and the faucet. DRIPPING GIVES THE FREEZING WATER SPACE TO DYNAMICALLY EXPAND INTO AND PREVENT BURSTING.
Q: We know plastic and copper pipes lack the flexibility to withstand the pressure differentials of freezing and unfreezing. Is there a pipe developed to withstand this pressure?
A: Yes, its called PEX https://en.wikipedia.org/wiki/Cross-linked_polyethylene . PEX has drawbacks if googled, but has expansion qualities up to 3 times that of traditional copper or PVC.