Is it safe to store drinking water in winter?
A host of organizations that promote emergency preparedness—the Red Cross; the Centers for Disease Control and Prevention and the Federal Emergency Management Agency in the US; and Canada’s Office of Public Safety—all recommend storing drinking water in clear “food-grade” plastic containers when keeping it for long periods of time (but they advise against storing water for more than six months). Containers can include anything that has been approved by a regulatory agency, such as the Canadian Food Inspection Agency. One option is a two-litre pop bottle. Avoid glass, containers that have held anything toxic, and those that are hard to clean or seal tightly.
According to Health Canada, there is no “substantiated evidence” that freezing bottled water releases toxic chemicals from the plastic. As well, says Andrew Barton, manager of the Safe Water Program with the Grey Bruce Health Unit, any bacterial reproduction in the water will slow down as the temperature drops and stop altogether when the water freezes. “So, from a bacterial point of view, freezing is, if anything, beneficial,” he says.
From a practical point of view? Maybe not so much. “In principle, it’s certainly possible that the container could crack when the water freezes,” says Ernie McFarland, professor emeritus in the physics department at the University of Guelph, especially if there’s no space for expansion. “When water freezes, the resulting ice has a volume about eight per cent greater than the original volume of the water,” he explains. The thicker the plastic, the better it will stand up to freezing, says Fred Edgecombe, technical consultant for the Canadian Plastics Industry Association. He suggests avoiding 500-ml bottles, as they’re “literally paper thin.” But that two-litre pop bottle, while still relatively thin, will probably be okay, as long as you don’t fill it all the way (three-quarters allows plenty of room for expansion).
Results of the Cottage Life simulation test with a freezer confirm this. The same two-litre pop bottle survived multiple freezing and thawing sessions with no cracks or leaks.