A Calm, Ordered Shutdown That Protects Your Pipes, Your Backflow Preventer and Your Spring
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There is a particular kind of fall afternoon that seems made for this job. The lawn has stopped growing, the air smells of leaves, and the garden hose is still lying in a loose coil by the back step where you left it in August. It is easy to think of shutting down your outdoor water as a small chore. In reality, you are draining a system of pipes that runs from the warm inside of your home out into soil and air that will spend months below freezing.
What makes this work worth doing carefully is that the damage rarely shows itself right away. A split in a frost-free tap or a cracked backflow valve can sit quietly all winter and only reveal itself in April, when you turn the water back on and find a puddle in the basement or a fountain in the flower bed. The good news is that almost all of that damage comes from a handful of predictable mistakes, and every one of them can be avoided with the right order of steps and a little patience.
This guide walks you through the whole afternoon in the sequence that protects your system best. You will start by picking your deadline from your local frost date, gather a short list of tools, shut down your outdoor taps, and then drain or blow out your sprinkler system zone by zone. Along the way, you will find a step-by-step table you can keep open on your phone, a look at how Canadian cities handle backflow testing, and a short list of things to note now so spring startup goes smoothly.
The simplest way to choose your shutdown weekend is to look at when frost usually arrives where you live. The Canadian Climate Normals from Environment and Climate Change Canada record the average date of the first fall frost at weather stations across the country, based on thirty years of observations from 1991 to 2020. Those dates vary far more than most people expect, so a shutdown that is perfectly timed in Toronto would be weeks late in Edmonton.
A few gentle cautions help you read this table well. These are airport stations, and city centres often stay a little warmer and frost a little later than the airport that carries the city's name. A normal is also an average, not a promise, so any given year can bring frost a week or two early. That is why the suggested windows sit ahead of the average date rather than on it.
It is tempting to wait for a warm Saturday, but the pipes care about the coldest hour of the night. The same climate normals show that the average October overnight low is already below freezing in Winnipeg, Calgary and Edmonton, and only a few degrees above it in Ottawa, even while daytime averages feel comfortably mild. If your forecast shows a hard freeze coming overnight, that is your signal to move the job up, even if the afternoon looks lovely.
If you also own a pool, it is worth coordinating the two jobs, since they share the same deadline logic.
For a deeper look at timing a pool shutdown against these same frost dates, see our guide to pool closing in Canada.
The simplest way to choose your shutdown weekend is to look at when frost usually arrives where you live. The Canadian Climate Normals from Environment and Climate Change Canada record the average date of the first fall frost at weather stations across the country, based on thirty years of observations from 1991 to 2020. Those dates vary far more than most people expect, so a shutdown that is perfectly timed in Toronto would be weeks late in Edmonton.
A few gentle cautions help you read this table well. These are airport stations, and city centres often stay a little warmer and frost a little later than the airport that carries the city's name. A normal is also an average, not a promise, so any given year can bring frost a week or two early. That is why the suggested windows sit ahead of the average date rather than on it.
It is tempting to wait for a warm Saturday, but the pipes care about the coldest hour of the night. The same climate normals show that the average October overnight low is already below freezing in Winnipeg, Calgary and Edmonton, and only a few degrees above it in Ottawa, even while daytime averages feel comfortably mild. If your forecast shows a hard freeze coming overnight, that is your signal to move the job up, even if the afternoon looks lovely.
If you also own a pool, it is worth coordinating the two jobs, since they share the same deadline logic.
For a deeper look at timing a pool shutdown against these same frost dates, see our guide to pool closing in Canada.
Most of what you need is already in your garage. Gather these before you start, so you are not walking back and forth with a dripping tap behind you:
If your sprinkler system will be blown out, the compressor is the one item that deserves real thought. What clears water from a line is the volume of air moving through it, not how hard the air is pushed. Hunter Industries gives a simple rule: take the flow of your largest zone in US gallons per minute and divide it by 7.5 to find the cubic feet per minute your compressor needs to deliver. Your system's design sheet or the nozzle ratings on the manufacturer's website will tell you the zone flow.
Many small garage compressors are built for inflating tires and running nail guns, and they simply cannot keep enough air moving to push water out of a long run of pipe. When the air volume falls short, it tends to slide over the top of the water and leave puddles sitting in the low spots, which is exactly where freeze damage starts. If you find your compressor struggling to keep the sprinkler heads popped up, that is a clear sign to rent a larger one or call an irrigation professional.
Compressed air can injure you in ways that are easy to underestimate. The Canadian Centre for Occupational Health and Safety warns that it can drive debris into your eyes and skin, enter the body through the ears, nose or a small cut, and in rare cases cause a dangerous air bubble in the bloodstream. Wear safety glasses the whole time, never stand or lean over sprinkler heads, valves or pipe while the system is under air, and keep children and pets well away.
If this afternoon is part of a bigger plan to head south for the winter, your outdoor shutdown is one piece of a larger checklist.
You can pair it with our Canadian checklist for winterizing before you leave.
Start by stepping outside and looking closely at each hose tap, sometimes called a hose bib or sillcock. A standard tap has its valve right at the handle, so the water sits in the pipe just behind the wall and on the outside of your home. A frost-free tap looks similar from the outside but has a long body that reaches back through the wall, placing the actual valve several inches inside your heated home.
Frost-free taps are wonderful, but they only work when two conditions are met. According to Woodford Manufacturing, the tap must be installed with a slight downward slope toward the spout, and nothing can be attached to the nozzle. A hose left connected traps water inside the long body, and that trapped water can freeze and split the tube. Many of these taps even carry a small reminder on the wall flange telling you to remove the hose.
With your taps identified, head indoors and find the shut-off valve that feeds each one. It is usually in the basement or a utility room, on the pipe that runs toward the outside wall where the tap is mounted. Set your bucket and towel underneath it before you touch anything.
The City of Toronto notes that outdoor faucets are the first part of a home's plumbing to freeze, and its advice follows the same order you will use here: unscrew the hoses, turn off the outdoor supply, and let the taps drain. In practice, the sequence looks like this:
That third step is the one people skip, and it matters more than it looks. When a pipe is only partly empty, a small plug of ice can form and seal the line, and any water still behind that plug has nowhere to go as it freezes. Engineering research from The Madison Group found that this sealed-plug effect, rather than simple expansion, is what usually causes pipes to burst. Opening the bleed cap removes the water that would otherwise be trapped between the valve and the wall.
A frost-free tap usually has no separate indoor shut-off and drains itself when you close it, as long as the hose is off. If yours also has an indoor valve, it does no harm to close that too.
Once each line is empty, slip an insulated cover over any tap that remains exposed, pressing it snug against the siding to block cold wind. Drain your hoses by lifting them hand over hand from one end, coil them loosely, and store them somewhere they will not freeze and crack. Before you move on, put a small piece of tape or a tag on each indoor valve that says "Outdoor tap – closed for winter," so nobody in the house opens it by mistake on a mild day in February.
The Insurance Bureau of Canada encourages homeowners to insulate vulnerable lines and know where their water shut-offs are before the cold arrives, and a labelled valve is a simple way to make that knowledge stick. Canadian insurers such as Square One also name closed and drained outdoor faucets among their frozen-pipe prevention steps, which gives this small job real weight.
For the full picture of how pipes freeze indoors and what to do if one does, our hub on frozen pipes in Canadian homes covers prevention and thawing in detail.
Start by stepping outside and looking closely at each hose tap, sometimes called a hose bib or sillcock. A standard tap has its valve right at the handle, so the water sits in the pipe just behind the wall and on the outside of your home. A frost-free tap looks similar from the outside but has a long body that reaches back through the wall, placing the actual valve several inches inside your heated home.
Frost-free taps are wonderful, but they only work when two conditions are met. According to Woodford Manufacturing, the tap must be installed with a slight downward slope toward the spout, and nothing can be attached to the nozzle. A hose left connected traps water inside the long body, and that trapped water can freeze and split the tube. Many of these taps even carry a small reminder on the wall flange telling you to remove the hose.
With your taps identified, head indoors and find the shut-off valve that feeds each one. It is usually in the basement or a utility room, on the pipe that runs toward the outside wall where the tap is mounted. Set your bucket and towel underneath it before you touch anything.
The City of Toronto notes that outdoor faucets are the first part of a home's plumbing to freeze, and its advice follows the same order you will use here: unscrew the hoses, turn off the outdoor supply, and let the taps drain. In practice, the sequence looks like this:
That third step is the one people skip, and it matters more than it looks. When a pipe is only partly empty, a small plug of ice can form and seal the line, and any water still behind that plug has nowhere to go as it freezes. Engineering research from The Madison Group found that this sealed-plug effect, rather than simple expansion, is what usually causes pipes to burst. Opening the bleed cap removes the water that would otherwise be trapped between the valve and the wall.
A frost-free tap usually has no separate indoor shut-off and drains itself when you close it, as long as the hose is off. If yours also has an indoor valve, it does no harm to close that too.
Once each line is empty, slip an insulated cover over any tap that remains exposed, pressing it snug against the siding to block cold wind. Drain your hoses by lifting them hand over hand from one end, coil them loosely, and store them somewhere they will not freeze and crack. Before you move on, put a small piece of tape or a tag on each indoor valve that says "Outdoor tap – closed for winter," so nobody in the house opens it by mistake on a mild day in February.
The Insurance Bureau of Canada encourages homeowners to insulate vulnerable lines and know where their water shut-offs are before the cold arrives, and a labelled valve is a simple way to make that knowledge stick. Canadian insurers such as Square One also name closed and drained outdoor faucets among their frozen-pipe prevention steps, which gives this small job real weight.
For the full picture of how pipes freeze indoors and what to do if one does, our hub on frozen pipes in Canadian homes covers prevention and thawing in detail.
Your sprinkler system has its own shut-off valve, usually in the basement near the water meter or in an underground valve box in the yard. Close it completely. Some systems use a stop-and-waste valve buried below the frost line, which you turn with a long key.
Next, decide what to do with the controller. Rain Bird's homeowner winterization guide recommends that systems without a pump simply set the controller to Off or Rain mode and leave it plugged in, because the small amount of heat from the transformer helps keep condensation away from the circuit board. If your system has a pump, the advice changes: the controller should be unplugged, or its common wire disconnected, since a power surge could restart the schedule and damage a pump running dry. Hold off on switching the controller off until the blow-out is finished if you plan to use it to open zones.
Sprinkler systems in cold climates are generally built to be emptied in one of two ways. Some have manual drain valves at the low points of the pipe, and some rely on compressed air. If you are unsure which kind you have, the safer choice is to blow the system out.
The Colorado State University Extension goes a step further and advises against trusting gravity drains alone, because buried pipe shifts over the years and water collects in low spots you cannot see. It also points out that systems with electric zone valves need compressed air to clear the water sitting above each valve's diaphragm. If your system does rely on manual drains, relieve the pressure first by opening a zone, then open each drain valve slowly, since the mainline is still holding pressure when you begin.
This is where much of the advice online becomes confusing, so it helps to know what the manufacturers actually say. Hunter Industries sets its limits by pipe type: no more than 50 psi for flexible black polyethylene pipe and no more than 80 psi for rigid white PVC. Its guidance adds an important condition, which is that the pressure must stay below the rating of the weakest component in each zone, including sprinkler nozzles and fittings.
Rain Bird's homeowner guide is simpler and stricter. It says air pressure must not exceed 50 psi, for any system, and that a pressure regulating valve must be used. The reason is that air behaves very differently from water. A system that happily holds much higher water pressure can still be damaged by air, because air moves faster, heats the pipe as it rushes through, and hits fittings harder when it reaches the end of a line.
Putting those together, a calm and reliable rule for most homeowners is to set your regulator to 50 psi and leave it there. That setting sits within every manufacturer's limit for both types of pipe. Treat 80 psi as a ceiling for rigid PVC, not a target, and only if you know every component in the zone is rated for it.
With the water off and your safety glasses on, you are ready for the heart of the afternoon. Work through these steps in order:
Two cautions from the manufacturers deserve a moment of attention. First, never run the compressor against closed valves, and never fill the compressor's tank and release that stored blast into a closed mainline to make up for a small compressor. Second, more air is not better. Once a zone is dry, air rushing through empty pipe creates friction and heat, and sprinkler heads with plastic gear drives depend on water to stay cool and lubricated. Several short cycles protect your system far better than one long one.
Your backflow preventer is the brass assembly, often mounted above ground near the house, that stops irrigation water from flowing back into your drinking water. Its internal parts and brass body are among the most vulnerable pieces of the whole system, so it gets its own careful handling.
Air should never be blown through the backflow device itself. Connect your compressor downstream of it, blow out the zones, and drain the backflow preventer afterward. The winterization instructions for the widely used FEBCO Model 765 pressure vacuum breaker from Watts explain that the assembly cannot be fully drained through its small test cocks alone, and that the outlet shut-off should be closed while you blow out the lines below it.
When the zones are done, open and close the two ball-valve handles a few times to release any trapped water, then leave both handles and the test cocks at a 45-degree angle, halfway between open and closed. That angle matters because a ball valve left fully open or fully closed can hold a pocket of water between the ball and the valve body, and that pocket is exactly what cracks the brass when it freezes. Your main irrigation shut-off, meanwhile, stays fully closed all winter.
If your assembly sits in a sheltered spot, an insulated cover gives it extra protection. In some cities, though, a registered backflow device may not be removed, so check local rules before you unscrew anything.
Drip zones often include a pressure regulator and a filter, and the small emitters and tubing are usually rated for much lower pressures than spray heads. Because the safe blow-out pressure is limited by the weakest part of a zone, check the ratings on your drip components before sending air through them, and use the lowest pressure that still moves the water out.
Flow sensors are another part to handle with care. Hunter recommends removing them and sealing the pipe before blowing out, since the rush of air can damage them. Rain sensors with a collection cup need little more than emptying and a plastic bag over the top.
Once everything is dry, your controller can go to its winter setting.
If you are thinking about upgrading before next season, our look at smart sprinkler controllers for Canadian summers explains what the newer models can do.
Your sprinkler system has its own shut-off valve, usually in the basement near the water meter or in an underground valve box in the yard. Close it completely. Some systems use a stop-and-waste valve buried below the frost line, which you turn with a long key.
Next, decide what to do with the controller. Rain Bird's homeowner winterization guide recommends that systems without a pump simply set the controller to Off or Rain mode and leave it plugged in, because the small amount of heat from the transformer helps keep condensation away from the circuit board. If your system has a pump, the advice changes: the controller should be unplugged, or its common wire disconnected, since a power surge could restart the schedule and damage a pump running dry. Hold off on switching the controller off until the blow-out is finished if you plan to use it to open zones.
Sprinkler systems in cold climates are generally built to be emptied in one of two ways. Some have manual drain valves at the low points of the pipe, and some rely on compressed air. If you are unsure which kind you have, the safer choice is to blow the system out.
The Colorado State University Extension goes a step further and advises against trusting gravity drains alone, because buried pipe shifts over the years and water collects in low spots you cannot see. It also points out that systems with electric zone valves need compressed air to clear the water sitting above each valve's diaphragm. If your system does rely on manual drains, relieve the pressure first by opening a zone, then open each drain valve slowly, since the mainline is still holding pressure when you begin.
This is where much of the advice online becomes confusing, so it helps to know what the manufacturers actually say. Hunter Industries sets its limits by pipe type: no more than 50 psi for flexible black polyethylene pipe and no more than 80 psi for rigid white PVC. Its guidance adds an important condition, which is that the pressure must stay below the rating of the weakest component in each zone, including sprinkler nozzles and fittings.
Rain Bird's homeowner guide is simpler and stricter. It says air pressure must not exceed 50 psi, for any system, and that a pressure regulating valve must be used. The reason is that air behaves very differently from water. A system that happily holds much higher water pressure can still be damaged by air, because air moves faster, heats the pipe as it rushes through, and hits fittings harder when it reaches the end of a line.
Putting those together, a calm and reliable rule for most homeowners is to set your regulator to 50 psi and leave it there. That setting sits within every manufacturer's limit for both types of pipe. Treat 80 psi as a ceiling for rigid PVC, not a target, and only if you know every component in the zone is rated for it.
With the water off and your safety glasses on, you are ready for the heart of the afternoon. Work through these steps in order:
Two cautions from the manufacturers deserve a moment of attention. First, never run the compressor against closed valves, and never fill the compressor's tank and release that stored blast into a closed mainline to make up for a small compressor. Second, more air is not better. Once a zone is dry, air rushing through empty pipe creates friction and heat, and sprinkler heads with plastic gear drives depend on water to stay cool and lubricated. Several short cycles protect your system far better than one long one.
Your backflow preventer is the brass assembly, often mounted above ground near the house, that stops irrigation water from flowing back into your drinking water. Its internal parts and brass body are among the most vulnerable pieces of the whole system, so it gets its own careful handling.
Air should never be blown through the backflow device itself. Connect your compressor downstream of it, blow out the zones, and drain the backflow preventer afterward. The winterization instructions for the widely used FEBCO Model 765 pressure vacuum breaker from Watts explain that the assembly cannot be fully drained through its small test cocks alone, and that the outlet shut-off should be closed while you blow out the lines below it.
When the zones are done, open and close the two ball-valve handles a few times to release any trapped water, then leave both handles and the test cocks at a 45-degree angle, halfway between open and closed. That angle matters because a ball valve left fully open or fully closed can hold a pocket of water between the ball and the valve body, and that pocket is exactly what cracks the brass when it freezes. Your main irrigation shut-off, meanwhile, stays fully closed all winter.
If your assembly sits in a sheltered spot, an insulated cover gives it extra protection. In some cities, though, a registered backflow device may not be removed, so check local rules before you unscrew anything.
Drip zones often include a pressure regulator and a filter, and the small emitters and tubing are usually rated for much lower pressures than spray heads. Because the safe blow-out pressure is limited by the weakest part of a zone, check the ratings on your drip components before sending air through them, and use the lowest pressure that still moves the water out.
Flow sensors are another part to handle with care. Hunter recommends removing them and sealing the pipe before blowing out, since the rush of air can damage them. Rain sensors with a collection cup need little more than emptying and a plastic bag over the top.
Once everything is dry, your controller can go to its winter setting.
If you are thinking about upgrading before next season, our look at smart sprinkler controllers for Canadian summers explains what the newer models can do.
Keep this table open on your phone while you work. The times are approximate hands-on estimates for a typical home with two outdoor taps and a four- to six-zone sprinkler system, so allow extra time for a larger yard.
Backflow preventers protect the public water supply, so many municipalities regulate how they are installed and tested. The rules differ quite a bit from one place to the next, which is why it is worth a quick look before you remove, replace or test anything.
In Calgary, the City's cross connection control program ties the test to the start of each irrigation season under section 39.3(e) of the Water Utility Bylaw, which means your fall shutdown and your spring test go hand in hand. The City sends reminder notices, and the tester must be registered with Calgary Water Services.
In Edmonton, EPCOR's cross connection control rules require every testable backflow preventer to be tested annually by a certified tester, and non-testable devices to be visually inspected.
On the West Coast, the City of Surrey requires a certified tester with a Surrey business licence to test devices every year.
Across the water in Greater Victoria, the Capital Regional District sets a three-year cycle for residential irrigation devices.
In Ontario's two largest cities, the programs are built around bigger buildings. Toronto's Backflow Prevention Program applies to industrial, commercial and institutional properties, larger residential buildings and construction sites.
Ottawa's Water By-law No. 2025-227 applies to similar properties and to others the City considers a hazard, and it does not allow a registered device to be removed except to repair or replace it. If you live elsewhere, a quick call to your water utility will tell you whether your device is registered and how often it needs testing.
A shutdown is maintenance, not a test. Draining your backflow preventer and leaving its valves at 45 degrees is something you can do yourself, but repairing, replacing or officially testing a testable device is work for a certified tester or licensed plumber in most Canadian cities.
A confident homeowner can handle this whole afternoon, and there are still good reasons to call a professional. Consider hiring help if:
Rain Bird, Hunter and Watts all point homeowners toward a qualified contractor in exactly these situations, and many irrigation companies bundle fall blow-out with spring startup.
While you are already in the basement, it is a good moment to look at your other winter water defences too.
Our sump pump and backwater valve winter check walks through that list.
Before you put the tools away, spend ten minutes writing down what you did. Note where each indoor shut-off is, which ones you closed, which valves you left at 45 degrees, and any drips, cracked heads or slow zones you noticed. Take a quick photo of the backflow preventer with its handles in the winter position. When spring arrives, these notes turn a guessing game into a relaxed checklist.
When the last hard frost has passed, reverse the process slowly. Close the test cocks and bring the backflow preventer's ball valves to their closed position before you turn any water on, because they must be closed before the system is pressurized. Then open the main irrigation valve a little at a time, and open the backflow's ball valves slowly as well, since a sudden rush of water can cause water hammer that damages fittings.
For your outdoor taps, the first time you open each one in spring is the moment to look and listen. A frost-free tap that split over the winter often shows no sign until water flows again, because the break sits beyond the valve. Have someone stand indoors near the wall where the tap enters while you turn it on, and watch for any dampness in the ceiling or wall.
If you are in Calgary or another city that ties testing to startup, book your certified tester before you switch the system on.
If you do discover a leak inside the wall, our step-by-step guide for when a pipe bursts will help you act quickly.
With the notes written and the valves set, you have done everything that matters. Your pipes are empty, your brass is protected, and your spring will start with water in the garden instead of on the basement floor.
About the Author
Ryan is the founder of Homeowner.ca and a proud Canadian homeowner based in Guelph, Ontario. Over his 25-year career in digital publishing, he has focused on transforming complex information into clear, practical guidance that helps people make confident, well-informed decisions.
Yes. A frost-free tap only drains itself when nothing is attached to the spout. A connected hose traps water inside the long body of the tap, and that water can freeze and split the tube, usually without any visible sign until spring.
Set your compressor's regulator to 50 psi. That stays within every major manufacturer's limit for both polyethylene and PVC pipe. Hunter allows up to 80 psi for rigid PVC, but only as a maximum and only if every component in the zone is rated for it.
Sometimes, but many small compressors cannot move enough air. Divide your largest zone's flow in US gallons per minute by 7.5 to find the cubic feet per minute you need. If the sprinkler heads drop back down while air is flowing, the compressor is too small for the job.
About two minutes at a time, then move on to the next zone. Repeat the cycle once or twice until only a fine mist comes from the heads. Running air through a dry zone heats the pipe and can damage sprinkler heads with plastic gears.
No. Connect the compressor downstream of the backflow preventer, blow out the zones, and then drain the device separately. Its internal seals can be damaged by the heat of rushing air.
A ball valve left fully open or fully closed can hold a small pocket of water between the ball and the valve body. Leaving the handles halfway lets that water drain, so it cannot freeze and crack the brass.
It can be, if your system was designed with drains at every low point. Buried pipe can shift over time, though, and water collects where you cannot see it. Systems with electric zone valves need compressed air to clear the water above each valve's diaphragm, so if you are unsure, blow the system out.
For the shutdown itself, usually not. For testing, repairs or replacement, most Canadian cities with a program require a certified tester or licensed plumber. Calgary requires a test at every spring startup, Surrey requires one every year, and Greater Victoria requires one every three years for residential irrigation.
