Spring Sprinkler Startup Checklist

What to do

1. 🛡️Step 1

   Wait until the hard-freeze danger has passed

   Charging the system before the last hard freeze just re-creates the problem you spent the autumn avoiding, with the added irony of doing it deliberately. Use your area's average last spring freeze as the earliest sensible date, and give it a margin.

2. 💧Step 2

   Put the backflow device back together first

   Re-install it if you stored it, close the test cocks, refit the PVB bonnet and poppet, and leave the isolation ball valves at 45° for now — you want them part-open while the line behind them fills so air can escape rather than compress. They go fully open two steps on, once the system is full.

3. 💧Step 3

   Close every drain you opened in the autumn

   If you drained by gravity rather than blowing the system out, the boiler drain downstream of the shut-off and each zone's manual drain valve have been sitting open all winter. Walk the same route you took in the autumn and close them all, refitting any drain caps you removed. Automatic drain valves look after themselves — they reseat once the line has pressure — but a manual drain does not, and it will happily discharge at full mains pressure the moment you open the main.

   ⚠️Check the indoor boiler drain before anything else. It is the one that empties into a basement rather than onto grass.

4. 💧Step 4

   Open the main a quarter turn at a time

   Crack the irrigation shut-off open a quarter turn and listen. Let the mains fill for several minutes before opening it further, and take a few minutes to reach fully open. Once the system is full and quiet, open the backflow device's two isolation ball valves the rest of the way as well — they were left at 45° for the fill, and a system left throttled there runs at low pressure all season and mimics exactly the weak, gurgling zones you are about to go looking for. This single step prevents most startup damage, and it costs nothing but patience.

   ⚠️Never open the main fully on an empty system. Water slamming into empty pipe is what cracks fittings and launches heads.

5. 🛡️Step 5

   Watch it hold pressure before you run anything

   With the system full but no zone running, stand at the backflow device for a minute and watch. Drips at the assembly, weeping valves, or the sound of water moving when nothing is on all point at a winter casualty — and they are far cheaper to find now than in July as a dead zone and a water-bill spike.

6. 💧Step 6

   Run every zone and walk it

   Run each zone for a few minutes and walk it while it sprays: clear clogged nozzles, straighten heads the winter heaved, re-aim anything watering the driveway, and replace cracked heads now rather than in the first heat wave. Check the controller's clock, program and backup battery while you are there.

7. 💧Step 7

   Set the schedule for spring, not for last August

   Whatever the controller was running when you shut it down was tuned for peak summer demand. Spring turf needs far less, and starting the season on August run times wastes water and encourages shallow rooting just as the lawn is establishing its depth for the year.

8. 💧Step 8

   Put the controller back in Run

   You parked it in the off or rain position in the autumn so it would hold its clock and program over winter, and it has been sitting there ever since. Move the dial or mode back to Run/Auto and confirm the next scheduled start time actually appears on the display. Then let one full cycle run on schedule and check it happened — a controller that is programmed but disabled looks completely normal until the lawn starts going off in July.

When is your last freeze?

The steps are the same everywhere — the deadline isn't. Enter your ZIP for the NOAA freeze normals at the station nearest you — free, no signup required.

Frequently asked questions

When should I turn my sprinkler system on in spring?

After the risk of a hard freeze has passed for your area — your average last spring freeze is the earliest sensible anchor, with a margin on top. Turning it on early and then getting a freeze puts you back where you started, deliberately.

Why does my sprinkler system need to be pressurised slowly?

Because water entering empty pipe at full mains pressure creates a shock wave — water hammer — that can crack fittings and blow heads off their risers. A quarter turn at a time over several minutes lets the pipe fill without the spike.

What should I check first at spring startup?

The backflow preventer, while the system is holding pressure but not running. It is the component most likely to have been damaged over winter and the one where damage is visible without digging.