3 different duration recommendations for same zone

I am completely puzzled and need help. I originally created one schedule for my three zones (grass and two drip zones) using flex monthly. Based on my zone configurations, it recommended the following durations which seemed reasonable based on prior watering:

Front Yard (drip): 32 minutes
Back Yard (drip): 47 minutes
Grass (fixed spray): 16 minutes

I am now separating my drip zones into a second schedule. As a first step, I created a schedule that is exactly the same as my original schedule, only change is I removed the grass zone. With no changes to zone configuration or anything else, the durations changed drastically in the new schedule:

Front Yard (drip): 2 hours 29 minutes
Back Yard (drip): 3 hours 43 minutes

And then it gets even more strange - if I remove the front yard drip zone from the new schedule, the back yard drip duration changes:

Back Yard (drip): 4 hours 4 minutes

So for identical zone configurations, I have three different suggestions for my back yard drip zone - 47 minutes, 3 hours 43 minutes, and 4 hours 4 minutes. And my front yard drip zone is either 32 minutes or 2 hours 29 minutes, depending on which of the other two zones are included in the same exact schedule.

Can someone explain this? Thank you!

Flex monthly is best used for similar type crops. It will water at the highest frequency zone and adjust other zone minutes to accommodate.


Thank you franz - your reply led me to an “aha” moment. Previously I assumed a single schedule would water only the zones that needed it. Now if I understand correctly, a schedule will always water all zones within it. And each zone may have different parameters that ultimately dictate how much water it needs to “fill up its bucket”.

So a schedule-per-zone (or per identical/very similar zones) should calculate the optimal duration and frequency for each zone, whereas a schedule with different zones may need to water differently as a compromise to ensure all zones get enough water over time.

In my case, having my grass zone included with drips forced the schedule to run each allowed day (Tuesday, Thursday and Saturday here in Las Vegas) - but since it was watering frequently for grass, the drip duration was shorter. Now that I’ve separated out the drips, the grass schedule still runs frequently but the drips run for several hours but only every week or two.

Flex monthly will “back into” the zones that have been chosen using the lowest common denominator frequency, which will ultimately affect durations. If you group similar type crops with the same characteristics it will land on a consistent frequency. Definitely put different crop types in different flex monthly schedules. Flex daily waters each zone independently so it doesn’t matter which zones are chosen. Think of it more like a container of zones that have the same start time.


That makes sense - unfortunately I’m in Las Vegas where our allowed days per week changes every three months and goes from 6 days per week in summer down to 3 days in fall and spring, and then 1 day in winter. Am I correct that flex daily may not work since most of the year is less than the recommended 4 days?

It “could” work. Maybe try one zone in flex daily and see what results you get?


I didn’t realize Vegas went to restrictions. Are you in LVVWD, Henderson, or NLV?

I live in Henderson but water is LVVWD. Here are our restrictions that I believe applies to the whole valley:

Sep-Oct: 3 days/week (Tue-Thu-Sat for me, days depend on address)
Nov-Feb: 1 day/week (Tue)
Mar-Apr: 3 days/week (Tue-Thu-Sat)
May-Aug: 6 days/week (All except Sun), no watering (even drips) from 11am-7pm