Seasonal Property Plumbing: Winterizing, Opening Up and Year-Round Conversion

Ontario seasonal properties: the plumbing context

Ontario has one of the highest concentrations of seasonal properties in Canada — lakefront cottages, seasonal cabins, and rural retreats throughout the Shield, Muskoka, Haliburton, Simcoe County, and beyond. Many of these properties were built for summer use only, with plumbing that was never intended to withstand Ontario winters or support year-round occupancy.

The trend in recent years has shifted significantly: a growing number of property owners are converting seasonal cottages into primary residences or four-season retreats. That shift requires a different approach to plumbing — one designed for consistent use, freeze protection, and compliance with current Ontario Plumbing Code standards.

Whether you are simply closing the property for winter or undertaking a full conversion, understanding what your plumbing requires at each stage protects the property, your investment, and the health and comfort of everyone who uses it.

Winterizing before closing (fall)

Proper winterization is the single most important plumbing task for a seasonal property. Done correctly, it eliminates frozen pipe risk entirely and protects fixtures and fittings through even the coldest Ontario winters. Done poorly — or not at all — the cost of spring repairs can be significant.

Step-by-step: shutting down for winter

• Shut off the water main — find the main shutoff and turn it fully off. This is the foundation of everything else.
• Open all supply faucets — hot and cold, at every fixture throughout the property. This releases pressure and allows water to drain from the pipes by gravity where possible.
• Flush all toilets and remove remaining water from the tank and bowl with a sponge. A small amount of RV antifreeze (propylene glycol) added to the bowl protects the trap.
• Drain the water heater — attach a garden hose to the drain valve and run it to a floor drain or outside. Turn off the gas or electricity first and let it cool.
• Drain inline filters and water softeners if present.
• Use a wet-dry shop vac to clear water from low points in supply lines that won't drain by gravity — particularly any horizontal runs.
• Pour RV antifreeze into every P-trap — under all sinks, in bathtubs, in showers, and into floor drains. Do not use automotive antifreeze, which is toxic. RV antifreeze (propylene glycol) is specifically designed for plumbing and is safe for this application.
• Disconnect and drain garden hose bibs — if not frost-free type, shut off the dedicated supply valve inside and drain the bibb completely.
• Document the location of the main shutoff — ideally photograph it so anyone arriving in spring knows where to find it.

Opening in spring: the checklist

The temptation when arriving at a seasonal property in spring is to turn on the water and get on with things. A few minutes of systematic checking first can catch problems before they become floods.

Common issues found in spring

Frozen or burst pipes from inadequate winterization

If winterization was incomplete — particularly if water was left in supply lines — a hard freeze can split the pipe. Copper typically cracks cleanly; PEX may simply expand and reseal. Galvanized or plastic fittings are common failure points. A burst is typically found immediately when the water is turned on — look for water spraying or pooling in the basement or walls.

Cracked valve seals

The elastomeric seals inside shutoff valves and faucet cartridges can shrink or crack during extreme cold. Old ball valves and compression-type fittings are particular risk areas. A valve that drips when re-opened after winter often just needs its packing or cartridge replaced.

Rodent-damaged insulation

Mice and squirrels are a real concern in vacant seasonal properties. Check pipe insulation in unconditioned spaces carefully — compromised insulation on supply pipes increases freeze risk the following winter and should be replaced.

Odours from dry traps

If RV antifreeze was not added to traps on closing, or if it evaporated, the trap seal may have dried out over winter. This allows sewer gas to enter the property. Running water through all fixtures on opening refreshes the traps.

Year-round conversion: what the plumbing requires

Converting a seasonal cottage or camp to year-round occupancy is a significant project, and plumbing is one of the primary areas requiring upgrade. Year-round use in Ontario means designing for temperatures that can reach -25°C or lower in Simcoe County, Muskoka, and Haliburton.

Supply line insulation and protection

Any supply lines running through unheated spaces — crawl spaces, exterior walls, uninsulated basements — must be protected. This may mean re-routing piping into conditioned space, adding proper pipe insulation, or installing heat trace (ULC-listed electric heat cable) on vulnerable runs. A licensed plumber assesses your specific layout and recommends the appropriate protection strategy.

Year-round water heater

Many seasonal properties have a small or older water heater that was adequate for summer use but undersized or poorly located for year-round demand. A year-round conversion typically requires a properly sized tank or on-demand (tankless) unit installed in a conditioned space with appropriate venting and gas or electrical supply.

DWV compliance

Drain, waste, and vent (DWV) systems in older seasonal builds may not meet current Ontario Plumbing Code requirements for year-round occupancy — particularly vent sizing and trap protection. A plumbing assessment identifies any non-compliant elements that should be updated.

Permit implications

Plumbing work associated with a year-round conversion typically requires permits. The local municipality will have specific requirements for the conversion — your plumber and contractor can guide you through the process.