Every April we get the same call: "It's nice out, can I turn the sprinklers on?" The answer isn't a calendar date — it's three conditions. If all three are green, go. If any one is still red, wait. Turning on too early is how a $90 spring opening turns into a $900 repair bill.
The three readiness conditions.
None of these are optional. Each one protects a different part of the system and a different part of your lawn.
Last hard frost is past
10-day forecast: 0°C+ overnightAny residual water in valves or fittings will freeze and crack the component if temps dip below freezing after pressurization. Wait until your local 10-day overnight forecast stays above 0°C consistently.
How to check: Open Environment Canada's 7-day forecast for your municipality, look at overnight lows.
Soil temperature 10°C+
At 6 inches deepCool-season grasses (everything in Ontario) don't actively grow until soil temp passes 10°C at root depth. Watering before that is wasted — moisture sits, fungi grow, grass doesn't drink. Soil lags air temp by 2-3 weeks in spring.
How to check: Use a soil thermometer or check your local soil-temp service. Or wait for forsythia to bloom — biological soil-temp indicator.
Ground is no longer frost-locked
Probe goes 8-10" easilyPressurizing a system before the ground has thawed shoves pipe upward through frost-heaved soil and breaks splices. The mainline can't move freely until the surrounding soil is fully thawed.
How to check: Push a long screwdriver 8-10 inches into the lawn in 3-4 spots, including the shaded north side. Easy push everywhere = good.
If all three are green, you can pressurize safely. If even one is borderline — particularly the soil thaw — wait another week. There is no scenario where rushing the start-up by five days is worth a cracked manifold.
"The single most expensive April call we run is a homeowner who turned on the system in shorts weather, got a frost the next night, and woke up to a hissing valve box and water under the deck. The 10-day forecast showed it. They didn't look. The forecast is your cheapest insurance."
Regional timing — Newmarket, Aurora & the GTA.
The GTA has a 7-10 day spread on safe turn-on dates, driven by latitude, elevation, and proximity to Lake Ontario. The downtown corridor warms first because of the urban heat island and lake-moderated overnight lows. King City, East Gwillimbury and the rural north warm last because they're further north, higher in elevation, and more open to overnight radiative cooling.
Here's the typical safe-to-open window for an average spring. In a cold spring, slide everything 7-14 days later.
| Region / Municipality | Typical safe-to-open | Why |
|---|---|---|
| Toronto core / Lakeshore | Mid-April | Urban heat island + lake-moderated overnight lows |
| Vaughan / Markham / Richmond Hill | Mid–late April | South GTA, lower elevation |
| Thornhill | Mid–late April | South GTA / city border |
| Aurora | Late April | Mid-York Region, slightly higher elevation |
| Stouffville | Late April – early May | Open rural land, slower thaw |
| Newmarket | Late April – early May | Northern York Region |
| King City (uplands) | Early May | Highest elevation in York, latest thaw |
| East Gwillimbury | Early May | Furthest north in our service area |
These are starting points, not guarantees. The three readiness conditions trump the table. A normal-spring late April for Aurora can become mid-May in a cold year — check the conditions, not the calendar.
What turning on too early actually costs.
Three failure modes, in order of likelihood and cost.
Real numbers, real callouts
- Frost-cracked valve manifold — $379.90 to $829.70. Residual water freezes overnight after a too-early pressurization, splits the manifold or a valve body. Master pricing on full manifold replacement: $95 service call + $135 (3-valve manifold) or $285 (6-valve manifold) + $74.95 per valve replaced. Caught the next morning when the homeowner sees water in the valve box. Common in early-April starts followed by a cold snap.
- Frost-heaved lateral break — $250-$600. Pressurizing on still-frozen ground pushes pipe upward, splits a splice. Often invisible until the system is run and a brown-then-green-then-brown pattern emerges in the lawn over a couple weeks.
- Cold-soil fungal pressure — $0 in equipment, but a stressed lawn. Watering at 5°C soil temp soaks the surface without root uptake. Fungi like dollar spot, leaf spot, and pink snow mould thrive. The lawn comes out of spring weaker than it went in.
The cheapest of these failures is more expensive than waiting an extra week. Wait the week.
The 10-minute pre-check before turn-on.
Even when all three conditions are green, do this walk before turning the water on. It catches 30% of springtime damage before you pressurize and turn a small problem into a big one.
- Walk every zone and look at every head. Cracked bodies, missing nozzles, mulch piled up, sunk below grade — flag anything that looks off.
- Check the backflow assembly visually. Insulation jacket removed, no visible cracks, no dripping. Don't open or test it — that's regulated and requires a certified tester.
- Probe the ground in 3-4 spots, including the north / shaded side of the house, with a screwdriver or soil probe. Easy 8-10" push everywhere = green light.
- Check the controller. Plugged in, display lit, all zones showing. If it was unplugged for winter, plug it in and let it sit 24 hours before re-programming.
- Locate the main shut-off. Confirm you know where it is and that the valve handle moves. You'll need to open it slowly during pressurization.
If anything from the walk looks broken, book a spring opening with us instead of pressurizing yourself — we'll diagnose, repair, and pressurize in one visit. Cheaper than fighting through it solo.
When to just call us.
You don't have to DIY any of this. PJL spring openings include:
- Slow pressure-up while watching the gauge
- Full leak diagnostic — listening, walking, watching for pooling
- Zone-by-zone walkthrough with you
- Hydrawise re-program for the new season
- Minor head adjustments included
- Same-day repair quotes if anything's broken from winter
- 1-year guarantee on any repair work done
Spring opening pricing starts from $90 for a typical residential 4-6 zone system. We're booking late April through end of May right now — bookings made in early April get the best slot selection.
Book your spring opening.
Across Newmarket, Aurora, King City, Richmond Hill, Vaughan, Markham, Stouffville, East Gwillimbury and Thornhill. Slots fill fast in the first two weeks of May — book now to lock your week.
Book a spring openingThe bottom line
Forget the date. Check the three conditions: forecast above freezing, soil at 10°C, ground thawed deep. If all three are green, go — carefully, slowly, with eyes open. If you'd rather skip the gamble, book a spring opening or call (905) 960-0181. We've pressurized thousands of GTA systems coming out of winter and we know exactly what to listen for.