What needs to be done to our septic before winter?

We are new cottagers. What do we need to do to our septic system or tank when we close up for the winter?
—Amy Leslie, Crowe lake, Ont.

Basically nothing—assuming your septic system is properly installed and insulated, and there won’t be any snow machines driving over the tank or drain field in the winter. (A plow, for example, could damage pipes, compact the soil,
or dig up areas of the ground.) However, Max Burns, author of Country & Cottage Water Systems, says you should put RV antifreeze—about half a cup—in every toilet trap in the cottage, or you risk a cracked toilet bowl.

As for the tank itself, don’t have it pumped out right before you leave. An empty tank over winter could turn into a liability, says Sandy Bos, the on-site sewage system inspector for the Township of Muskoka Lakes and a member of the board of directors of the Ontario Onsite Wastewater Association.

“The tank could float if there was a high water table in the spring,” he explains. “Even a concrete tank will float.” If you’re going to empty the tank pre-cottage close-up, it’s better to do that in late summer, so you have some time to fill it up again (at least a little) before you leave.

One more point: If your system uses a pump to send the sewage uphill to the bed, it’s possible that the line going to the bed or tank could freeze. But again—this is unlikely if everything is properly installed and insulated. “If the line is down in the ground—and usually they are—there should be no problem,” says Doug Schultz, the chief building official for the Township of Whitewater Region, in the Ottawa Valley. “I haven’t heard of any of them freezing up.”

If you’re concerned, consult an expert; a plumbing contractor can show you how to winterize the system.