The time it takes to run a sprinkler to apply 1 inch of water depends on the sprinkler's precipitation rate (how many inches of water it applies per hour). Here's how to estimate it:

• Measure how much water your sprinkler applies in a set time (commonly 15 minutes) using catch containers like tuna cans placed around the lawn. For example, if your sprinkler applies 0.5 inches of water in 15 minutes, it will take 30 minutes to apply 1 inch (because 0.5" in 15 min means 1" in 30 min)

• Typical sprinkler application rates vary:
  • Pop-up spray heads: about 1.65 inches per hour
  • Rotor heads: about 0.75 inches per hour
  • Multi-stream heads: about 0.45 inches per hour

Using these rates, you can calculate run time with the formula:

Run Time (minutes)=Desired water depth (inches)×60Precipitation rate (inches/hour)\text{Run Time (minutes)}=\frac{\text{Desired water depth (inches)}\times 60}{\text{Precipitation rate (inches/hour)}}Run Time (minutes)=Precipitation rate (inches/hour)Desired water depth (inches)×60​

For example, with a pop-up spray head running at 1.65 inches/hour, to apply 1 inch:

1×601.65≈36 minutes\frac{1\times 60}{1.65}\approx 36\text{ minutes}1.651×60​≈36 minutes

Similarly, rotor heads at 0.75 inches/hour would take about 80 minutes to apply 1 inch

• In practice, many sprinklers apply about 0.4 to 0.5 inches per hour, so it can take roughly 90 to 120 minutes to deliver 1 inch of water, depending on system design and zone size

• To avoid runoff, watering is often split into shorter cycles with intervals for absorption, especially if the sprinkler applies water faster than the soil can absorb it

Summary:

Sprinkler Type| Typical Precipitation Rate (in/hr)| Approximate Time to Apply 1" of Water
---|---|---
Pop-up spray heads| 1.65| ~36 minutes
Rotor heads| 0.75| ~80 minutes
Multi-stream heads| 0.45| ~133 minutes
Average residential| 0.4 - 0.5| 90 - 120 minutes

To get the most accurate time for your system, perform a "tuna can test" by running the sprinkler for 15 minutes and measuring water depth in cans, then calculate the time needed to reach 1 inch accordingly

. Thus, running a sprinkler for 1 inch of water typically takes between 30 minutes to 2 hours depending on the system and conditions.