Septic systems in a Canadian winter: preventing frozen lines

A septic system that works well in summer can stop working in a deep cold snap. Wastewater arriving from the house is warm, and the soil and snow above the system usually insulate it. Problems start when that insulation is lost or when water sits still in a pipe long enough to freeze.

What makes a system freeze

• Compacted snow: driving, parking or snowmobiling over the tank or the leaching bed packs the snow and lets the frost go deeper.
• No snow cover in an early cold spell, or a bed that was left bare after work in the fall.
• Low or irregular use: a house left empty for weeks, or a cottage used only on weekends.
• A slow trickle from a leaking fixture, which can freeze little by little in the pipe.
• Pipes that are too shallow or not sloped properly, so water stays in them.

Before winter

• Let the grass grow a little longer over the system in the fall and leave the snow undisturbed on top of it.
• Mark the tank and the bed so nobody plows, drives or piles snow there by mistake.
• Fix leaks and make sure lids and risers are tight and insulated if needed.
• Book the pumping in the fall if it is due: a full tank is harder to deal with in the snow.

At a seasonal cottage

If the property is closed for the winter, follow the closing advice of your septic professional and your local authority. If you visit in winter, a system that sees little use cools down more easily: spread out water use over your stay rather than running all the loads at once.

If drains stop working in the cold

1. Reduce water use to avoid a backup in the house.
2. Do not pour antifreeze, salt or additives into the system, and do not light fires or use torches over the pipes.
3. Call a septic professional: they can locate the frozen section and thaw it safely, then look for the cause so it does not happen again.

Describe the problem in the form and septic professionals in your area get back to you.