$120 in October or $1,200 in April: the Irrigation Bill Ontario Homeowners Choose by Doing Nothing
Water left in the line does not sit there quietly. It expands.
In short
A sprinkler blowout in the GTA is a $80–180 job: compressed air pushed through each zone until the lines are empty, the isolation valve closed, the backflow assembly drained. One visit, under an hour on most properties.
Skip it and the water that stayed behind freezes. Freezing water expands by about nine per cent and does not care what is in the way — the backflow assembly above ground goes first, then the manifold, then the lateral lines.
The cruel part is the timing. Nothing happens in winter. You find out in April, when the system is pressurised for the season and water comes up through the lawn. And your insurer, if you ask them, will want to know what precautions you took.
What the two outcomes cost
Market quotes from GTA irrigation contractors, autumn 2026 — prices published by businesses that sell the work.
| Typical price | Notes | |
|---|---|---|
| Blowout, small system (4–6 zones) | $80–130 | Under an hour, one visit |
| Blowout, larger system (8+ zones) | $140–250 | Priced by zone count on most quotes |
| Spring start-up | $100–180 | Often sold as a package with the blowout |
| Replacing a cracked backflow assembly | $400–900+ | The part that freezes first, and it sits above ground |
| Repairing a split lateral line | $300–800 per break | Requires locating the break, then digging |
| Manifold or valve rebuild | $400–1,200 | Several failures at once is common after a hard winter |
The arithmetic is not subtle. One skipped blowout can cost more than a decade of doing it.
When exactly, in an Ontario autumn?
Book in September, schedule for October. The work has to land after you stop watering and before the first hard freeze — and in a normal southern Ontario year that means October into the first days of November.
Two things push people past the window. The first is that a light overnight frost is not the enemy; a sustained freeze is, and it arrives without an announcement. The second is that every irrigation contractor in the region is doing the same work in the same four weeks, so the date you call and the date they come are not the same date. That is the whole reason to book a month early — the same pattern as snow removal contracts, which sell out in autumn for the same reason.
Our booking calendar covers which trades fill up in which month across the year.
Why draining it yourself usually is not enough
It depends on how your system was built. Some have manual drain valves at the low points, and if you know where all of them are, gravity does most of the work. Most people do not know where all of them are.
Gravity also cannot empty what is sitting horizontally, and it cannot empty the backflow assembly, which is the brass device above ground that keeps lawn water out of your drinking water. That assembly is the most exposed and the most expensive small part in the system, and it is the one that splits.
The other half of the answer is pressure. A blowout uses a large volume of air at a controlled, relatively low pressure. A shop vacuum has nowhere near the volume; a small pancake compressor produces high pressure and little volume, which is the combination that wrecks heads and seals. The tool matters more than the technique here.
Do not assume insurance covers the spring surprise
Home policies commonly exclude or limit water damage caused by freezing where reasonable precautions were not taken. An irrigation system left full of water through an Ontario winter is precisely the fact an adjuster will ask about.
This is not a prediction about your policy — wordings differ, and only yours governs. It is a reason to read the freezing clause before you decide the blowout can wait until next year, and to ask your broker rather than your contractor. Nobody at the irrigation company can tell you what your insurer will do.
One thing people get wrong about backflow rules
Search for backflow requirements in Toronto and you will find a mandatory programme with surveys, certified testers and test reports filed with the City. It is real — and under the City of Toronto’s Backflow Prevention Program it applies to industrial, commercial, institutional and Part 3 residential properties, not to a single-family house.
So if you own a house, that testing regime is not your obligation. Your backflow device still matters for a different reason: it is the part of your irrigation system most likely to be destroyed by freezing, and replacing it is the most expensive small repair on the list above.
If you own or manage a multi-residential building of five units or more, or a commercial property, the programme does apply — and that is a survey and reporting obligation, not a seasonal one.
What a proper blowout includes
Red flags
What to do next
Do it this week, not in late October: count your zones, then call two companies and ask for a price and the first available date. The date is the part that runs out, not the price.
Compare home services in Ontario on Ontario24 and contact businesses directly. Ontario24 is a classified directory — we help you find and compare, and we do not vet anyone. Also useful: how to choose a landscaper and eavestrough cleaning, the other autumn job with a deadline.
Before you call anyone, it helps to know what this job should cost and what the next one will. What things cost in Ontario in 2026 puts 75 service prices in one table.
Frequently asked questions
Market quotes across the GTA generally run $80 to $180 for a residential system, depending on the number of zones, with larger properties priced higher. Compare that against a cracked backflow assembly or a split manifold, which is typically several hundred dollars and sometimes into four figures once excavation is involved.
Book in September, schedule for October. The work needs to happen after you stop watering but before the first hard freeze, and in a normal Ontario autumn that window is October into early November. Contractors fill their calendars in that window, so the booking date and the service date are two different things.
Only if the system was built with drain valves and you know where they are. Draining by gravity leaves water in low points and in the backflow assembly, which is the part that cracks. Compressed air at the wrong pressure damages heads and seals, so a shop vacuum or a small pancake compressor is not the right tool.
Water expands when it freezes. The vulnerable parts, in order: the backflow assembly above ground, the manifold and valves, then the lateral lines. Damage rarely announces itself in winter — you find it in spring when the system is pressurised and a line is spraying under the lawn.
Do not assume so. Policies commonly exclude or limit water damage caused by freezing where reasonable precautions were not taken, and an un-winterised irrigation system is exactly the kind of thing an adjuster asks about. Read your own policy wording before you decide to skip the service, and ask your broker rather than the contractor.
A backflow device is standard on irrigation systems because it keeps lawn water out of the drinking supply. Note that the City of Toronto’s mandatory backflow prevention programme, with its testing and reporting requirements, applies to industrial, commercial, institutional and Part 3 residential properties rather than to a single-family house.
Air blowout of every zone, shutting the isolation valve, draining and protecting the backflow assembly, and a short report on anything found. Ask whether the spring start-up is quoted separately — many companies sell the two as a package, which is fine as long as you know what each costs.
Sources and how current this is
Checked 18 September 2026. The scope of the mandatory backflow testing regime — industrial, commercial, institutional and Part 3 residential properties, with surveys updated at least every five years and testing by certified Cross Connection Control Specialists — comes from the City of Toronto Backflow Prevention Program; other municipalities run their own programmes, so check yours. Prices here are market quotes published by GTA businesses that sell the work, not an independent survey, and they move year to year. Insurance wording on freezing damage varies by policy and insurer and nothing here is a statement about your coverage — read your own policy and ask your broker. This is not legal or insurance advice. Ontario24 is a classified directory and does not winterise irrigation systems or vet the businesses listed.