How long should I run my sprinklers?
The clock on the controller is a guess until you measure what each zone actually puts down. Run a catch-can test, enter the average depth, and the tool scales it to the depth you want.
The tuna can test
UF/IFAS Extension walks through the same field test this calculator assumes: place several identical straight-sided containers in one irrigation zone, run the zone for a known number of minutes, measure the depth in each container, and average them. If one can is much lower than the rest, coverage in that zone is uneven and the heads need adjustment before you trust any run time.
- Same zone only — rotor and spray heads apply water at different rates
- Average every can — dry spots and overlap both show up in the spread
- Repeat per zone — set run times separately on the controller
The formula
UF/IFAS Extension gives two equivalent ways to get from your test to a run time:
- Application rate:
inches per hour = average depth × (60 ÷ test minutes) - Run time for a target depth:
minutes = test minutes × (target depth ÷ average depth)
Example. You ran a zone for 15 minutes and averaged ¼ inch in the cans. The rate is ¼ × 4 = 1 inch per hour. To apply ½ inch, run 15 × (0.5 ÷ 0.25) = 30 minutes. To apply a full inch, double that to 60 minutes.
University of Minnesota Extension uses the same precipitation-rate idea when setting controllers: if a zone applies 1.5 inches per hour and you want 0.5 inch in one cycle, set that zone for 20 minutes (0.5 ÷ 1.5 × 60).
Soak and cycle on slow soil
A long single run can puddle and run off before water reaches the roots. Kansas State Research and Extension describes watering in small amounts, switching zones while the first section absorbs, then returning — the soak-and-cycle method. Use the sessions split above to divide your target depth across several shorter runs on the same day.
Questions people actually ask
How long should I run my sprinklers?
There is no one answer — it depends on your heads, your water pressure, and your soil. Run a catch-can test in each zone, measure the average depth, and scale up to the depth you want. A zone that puts down ¼ inch in 15 minutes needs 60 minutes to reach 1 inch.
What is the tuna can test?
Place several straight-sided containers (tuna cans, coffee mugs, or rain gauges) within one sprinkler zone, run that zone for a set time, measure the water depth in each can with a ruler, and average the results. UF/IFAS Extension publishes the math to turn that average into a run time.
How much water does a lawn need per week?
University of Minnesota Extension uses 0.5 inch per irrigation cycle as an example target when setting run times — not a universal weekly total. Your soil, grass type, and weather change the real need. The can test tells you how long your system takes to deliver whatever depth you are aiming for.
Do I test every zone?
Yes. Rotor heads, spray heads, and drip zones all apply water at different rates. Minnesota Extension recommends auditing each zone separately and setting run times zone by zone on the controller.
Why split watering into shorter cycles?
On slow-draining soil, water runs off before it soaks in. Kansas State Research and Extension describes a soak-and-cycle approach: apply a small amount, let it absorb, then repeat — rather than one long run that puddles at the surface.
Sources
- UF/IFAS Extension — How to Calibrate Your Sprinkler System: catch-can placement, 15-minute test, multiplying average depth by 4 for inches per hour, and scaling run time to a target depth.
- University of Minnesota Extension — Auditing Home Lawn Irrigation Systems: test each zone separately, average catch-can depths, calculate precipitation rate, and set run times from a target depth per cycle.
- UC IPM — Determine Your Sprinkler Output: the catch-can test and converting average depth to an hourly application rate.
- K-State Research and Extension — Watering the Lawn: Soak and Cycle: measuring output with cans and splitting irrigation into soak-and-cycle runs on slow-draining soil.