Montague Lawn Irrigation System Runtime Calculator

For each station (zone) enter the precipitation rate.  If this is unknown you can estimate spray heads as 1.5-2.0 inches per hour* and rotors as .3-.6 inches per hour*.

* Rainbird 1800 12 head will apply 2.01 inches/hour at 30 psi and 12 foot spacing .   Other popup spray heads are similar.

** Small rotors such as the Rainbird 42SA may apply at rates as low as 1.8"/hr and Hunter PGJ will apply .30 "/hr in typical full circle configuration.   Pressure, nozzle selection, and spacing will affect the precipitation rate.  

Precipitation Rate

The rate at which water is applied by the irrigation system and commonly expressed in inches per hour.   Precipitation rate can be measured by placing a rain gauge in the lawn and watering for a period of time.   Precipitation rates can vary widely by sprinkler system so measurement is encouraged. 

Uniformity

All irrigation systems apply water in an uneven pattern.   The uniformity is commonly measured as Distribution Uniformity (DU).   Well designed sprinkler systems should have values above 75%.    Lower uniformity will require longer runtimes to insure that the dry areas get adequate water.

Days/Week and Starts per Day

Commonly sprinklers are commonly run multiple times per week.  Lawn watering is more effective in short duration as this reduces runoff and watering of turf below the root zone.   Enter 1 to show the total minutes per week.   If you water Monday, Wednesday, and Friday you would enter 3 days/week.  If the sprinklers start multiple times per day enter the number of starts.

Environment

Shaded areas require less water than those in full sun.

Turf Type

Cool season varieties (Ex. Blue Grass) require more water than warm season (ex. Bermuda).