How to Winterize Your Plumbing in Ontario Before the Cold Season

Ontario winters are serious. Temperatures in the GTA regularly drop below -10°C, and across much of the province, sustained cold below -20°C is a normal part of every winter. When those temperatures arrive and your plumbing is not prepared, the consequences can be catastrophic: a burst pipe can release hundreds of litres of water in minutes, causing tens of thousands of dollars in structural damage, flooring replacement, and mould remediation.

The good news is that a thorough winterization — done correctly and at the right time — provides genuine protection. This guide from Mechora Group's plumbing team covers every step in the process, from hose bib draining to cottage de-commissioning, with the practical detail Ontario homeowners need.

Why Winterizing Matters in Ontario

Water is unique among common substances in that it expands when it freezes — by approximately 9% by volume. When water inside a pipe freezes, the expanding ice creates enormous hydraulic pressure — enough to split copper, crack cast iron, and rupture PVC and CPVC fittings. The pipe itself does not always fail at the point of freezing; pressure builds inside the system and can cause failure anywhere between the ice blockage and an open fixture.

The freeze damage itself may not even be the worst part. Most burst pipe flooding events occur during the thaw, when the ice blocking the pipe melts and water flows freely through the crack or split. If no one is home at the time — common in Ontario winter when homeowners travel south or to their cottages — the water can run for hours or days before it is discovered.

Insurance claims for pipe freezing are one of the most common winter claims in Ontario. Many insurers have specific coverage conditions for freeze damage, including requirements to maintain minimum interior temperatures. Before winter, review your home insurance policy carefully.

When to Winterize in Ontario

For a primary residence, winterization is an ongoing seasonal habit rather than a single event. The critical preparatory steps should be completed before the first sustained freeze — typically between late October and mid-November across most of the GTA and southern Ontario.

Monitor extended weather forecasts in October. When a multi-day stretch of overnight temperatures at or below -5°C is approaching, your exterior hose bibs should already be drained, hoses disconnected and stored, and any exposed pipes in unheated spaces insulated.

For cottages and seasonal properties, full winterization should be completed before you leave for the last time in the fall — ideally before Thanksgiving weekend in Ontario, especially for properties in the Muskokas, Haliburton, Kawartha Lakes, and other northern regions where temperatures fall faster and earlier.

Complete Ontario Winterization Checklist

Step 1: Shut Off and Drain Exterior Hose Bibs

Your outdoor hose bibs (also called sillcocks or outdoor taps) are the plumbing element most commonly overlooked and most likely to cause a freeze problem. Here is what to do based on your type:

Standard hose bibs — older bibs without frost-free design — have the water shutoff right behind the faceplate, which means the outdoor portion of the pipe always contains water when open. For these, you must locate the indoor shutoff valve (typically in the basement on the wall closest to the outdoor bib location), shut it off, then go outside and open the bib to drain the remaining water from the exposed pipe. Leave the outdoor bib in the open position over winter to allow any remaining moisture to evaporate.

Frost-free hose bibs — the modern standard installed in most homes built since the 1990s — have the actual shutoff seat located inside the warm wall, 20–30 cm behind the exterior faceplate. When you turn off a frost-free bib, water drains backward out of the exposed exterior portion automatically. However, frost-free bibs only work if no hose is connected. A garden hose left attached prevents drainage and can cause freezing in even a frost-free bib. Disconnect all hoses before the first freeze regardless of your bib type.

Step 2: Disconnect and Store Garden Hoses

Even if your hose bib is frost-free, leaving hoses connected is a common cause of freeze damage. Beyond the bib itself, a hose left outside can split and crack in freezing temperatures, and water remaining in the hose creates pressure back on the connection. Drain hoses completely before storing them in a shed, garage, or basement.

Step 3: Insulate Exposed Pipes in Unheated Spaces

Any pipe running through a space that is not heated — crawl spaces, garages, uninsulated attic spaces, exterior wall cavities, and unfinished basement areas adjacent to exterior walls — is at risk of freezing. Insulate these pipes before the cold arrives:

• Measure and cut foam pipe insulation sleeves to fit, securing with tape at all joints and seams
• Pay particular attention to where pipes pass through exterior walls, floor joists, and rim joist areas
• For garage walls shared with the house interior where pipes run, ensure wall insulation is adequate
• In crawl spaces, also insulate the crawl space hatch to prevent cold air infiltration

Step 4: Know Your Main Water Shutoff Valve Location

Every adult in your household should know exactly where the main water shutoff valve is and confirm it operates freely before winter. In most Ontario homes, the main shutoff is located in the basement near the front of the house, where the water service line enters the foundation. It may be a gate valve (round wheel handle) or a ball valve (lever handle).

If your main shutoff valve is corroded, difficult to turn, or has not been operated in years, have a plumber service or replace it before winter. A valve that cannot be closed quickly in an emergency is a serious liability. Mechora Group's plumbing team can replace aging shutoff valves throughout the GTA.

Step 5: Maintain Minimum 13°C When Away

Turning your thermostat down to save energy when you travel in winter is sensible — but there is a floor. Most plumbing professionals and insurance policies specify a minimum of 13°C (55°F) throughout the home when unoccupied. This is warm enough to keep pipes in interior walls and under sinks above freezing.

If you have a programmable or smart thermostat, check whether it has a "freeze protection" or "away" mode that locks in a minimum temperature regardless of schedule. Inform a trusted neighbour or property manager that you are away and ask them to check on the property periodically.

Step 6: Open Cabinet Doors During Extreme Cold

Kitchen and bathroom vanity cabinets on exterior walls trap cold air next to the pipes inside. During extremely cold nights (below -15°C), open the cabinet doors under exterior-wall sinks to allow warm room air to circulate around those pipes. This is a simple, zero-cost measure that can make a meaningful difference during a cold snap.

Step 7: Let Taps Drip During Severe Cold

Allowing a thin trickle of water to flow from a faucet served by a vulnerable pipe is a well-known freeze prevention technique. Moving water is much harder to freeze than standing water, and even a slow drip keeps enough flow to prevent ice from fully blocking the pipe.

Reserve this for genuine extreme cold events — sustained temperatures below -20°C or polar vortex conditions. Running water constantly wastes water and may not be necessary for most winter nights. When you do let taps drip, run both the hot and cold handles slightly on fixtures served by vulnerable pipe runs.

Step 8: Check Attic Insulation Over Pipe Runs

In some older Ontario homes, water lines were run through or just below attic spaces — a practice no longer followed in new construction but common in homes built before modern building code improvements. If your home has pipes in attic areas, verify that adequate insulation separates them from the cold exterior air. Heat from below should be allowed to reach the pipes; insulation should be placed above and to the sides of the pipes, not below them on the ceiling surface.

Step 9: Swimming Pool and Irrigation System Winterization

Irrigation systems: Shut off the dedicated irrigation shutoff valve inside the home. Blow out each zone with compressed air through the backflow preventer, using a compressor rated for your system. Stand clear of lawn irrigation heads during blow-out. Drain and insulate the backflow preventer if it is above grade. Many homeowners hire an irrigation professional for this step.

Swimming pools: Pool winterization is its own discipline involving lowering water level, adding winterizing chemicals, blowing out all plumbing lines, plugging returns and skimmers, installing a winter cover, and winterizing any heat pump or gas heater. If you are unsure, a pool service professional handles this.

Step 10: Cottage and Seasonal Property Full Winterization

Winterizing a seasonal property — a cottage, vacation home, or any property left unheated over winter — requires fully draining the plumbing system so there is no water anywhere in the pipes to freeze. This is a significantly more involved process than heating-season winterization:

1. Shut off the main water supply — at the well pressure tank shutoff, the municipal service shutoff, or the pump breaker for well systems
2. Open all faucets and flush toilets repeatedly to drain as much water as possible
3. Drain the water heater tank completely via the drain valve, then open the pressure relief valve to break the vacuum and allow full drainage
4. Drain the pressure tank on well systems
5. Drain water treatment equipment (softeners, filters) according to manufacturer instructions
6. Use compressed air to blow remaining water from supply lines if accessible
7. Pour RV antifreeze into all drain traps — sink traps, toilet bowls, toilet tanks, floor drain traps — to prevent the P-trap water from freezing and cracking
8. Drain the toilet tank and bowl as completely as possible before adding antifreeze
9. Remove the water filter cartridge and store it inside with you if the cottage type is seasonal

RV-type propylene glycol antifreeze (pink coloured) is safe for plumbing use. Do not use automotive antifreeze — it is toxic and not appropriate for use in plumbing systems.

Pipe Insulation Types

Not all pipe insulation is equal. Here are the main options available to Ontario homeowners:

Foam pipe insulation sleeves (closed-cell polyethylene or rubber foam): The most common and practical option for DIY installation. Available at any hardware store in various sizes to match common pipe diameters. Provides moderate protection — sufficient for pipes in conditioned spaces that occasionally get cold, but may not be enough for pipes in spaces that reach sustained freezing temperatures.

Pipe heat tape / heat cable (self-regulating electric heat cable): Wraps around the pipe and provides active heating. Self-regulating types automatically increase heat output as temperature drops and reduce it as temperature rises, preventing overheating. Essential for pipes in spaces that regularly experience sustained freezing temperatures. Must be used with insulation over top to maximize efficiency. Ensure the cable is rated for your pipe material (some are not rated for PVC).

Fibreglass pipe insulation: Higher R-value than foam sleeves but more complex to install and must be kept dry (fibreglass loses R-value when wet). More common in commercial applications.

Spray foam: Useful for sealing air gaps and penetrations where cold air drafts across pipe runs — especially effective at rim joist areas in basements. Not a substitute for pipe insulation itself but an important complement.

What to Do If You Are Leaving for an Extended Period

If you are leaving your primary residence for more than a week during winter, take these additional precautions:

• Turn water off at the main shutoff valve and drain the system (or maintain heat at minimum 13°C)
• Tell a trusted neighbour or property manager and leave them an emergency contact number and spare key
• Consider a smart thermostat that allows remote temperature monitoring and alerts
• Consider a leak/water detection sensor near your main supply line or water heater that sends phone alerts
• Know how to reach your home insurer's emergency line if damage occurs while you are away

Hiring a Plumber for Winterization Services

Many Ontario homeowners confidently handle the basic checklist items themselves — disconnecting hoses, opening cabinet doors, turning down the thermostat. However, there are specific tasks where professional help is the right call:

• Replacing a malfunctioning or non-functional main shutoff valve
• Installing frost-free hose bibs to replace aging standard bibs
• Installing pipe insulation or heat cable in difficult-to-access crawl spaces
• Full cottage/seasonal property winterization including drain-down and antifreeze treatment
• Assessing whether pipes in a particular area of your home are at risk and recommending solutions

Mechora Group provides residential plumbing services including seasonal plumbing preparation throughout Toronto, Mississauga, Brampton, Vaughan, Markham, and Oakville. If you have concerns about your plumbing's readiness for an Ontario winter, contact us before the cold season arrives — not after a problem develops.