Protecting plumbing from freezing: preparing for a Québec winter
A frozen pipe is not the real problem. The real problem is what happens when it thaws.
Updated
Why a frozen pipe is dangerous
Water expands as it freezes. In a closed pipe, that expansion builds considerable pressure between the ice plug and the closed tap downstream — and that is often where the pipe fails, rather than at the ice itself.
The result is not immediately visible. While the ice plug is in place it acts as a stopper. It is on thawing that water starts moving again and the crack begins to leak, sometimes for hours before anyone notices.
The pipes most at risk
Risk is not spread evenly through a house. The sections exposed to cold and poorly heated freeze first:
- Outdoor taps and their supply line, if they were not drained in the fall
- Pipes running along an exterior wall, especially behind a closed cabinet
- Sections crossing an unheated garage, crawl space or attic
- Lines in a cottage or a home left unoccupied over winter
- The water service itself, during prolonged and intense cold
Before winter
Prevention is simple and takes one evening: close the indoor valve feeding each outdoor tap, then open the outdoor tap to drain the line. Insulate exposed sections with purpose-made sleeves. In deep cold, leave the cabinet door under the sink open if the pipe runs along an exterior wall — warm room air makes a real difference.
If you go away, do not shut the heating off entirely. Keeping the house at a minimum temperature costs far less than water damage.
If a pipe is already frozen
The classic sign: one tap gives a trickle or nothing at all while the others work normally. Leave that tap open — as the ice starts to melt, the water has somewhere to go and the pressure can escape.
Warm the suspect section gently: a hairdryer, a hot towel, a space heater at a safe distance. Never use a torch or open flame. The fire risk inside a wall cavity is real, and heating too aggressively can burst the pipe.
If you cannot locate the plug, if the pipe is inside a wall, or if you see any trace of moisture, call a plumber before the thaw does the job for you.