# Minimum runtime greater than zero minutes

I have a zone and it’s pretty tiny (2x herb trugs with drip).

The schedule says it is usually getting zero minutes. How can I ensure I get at least one minute of water each time as an absolute minimum? Surely there should be no combination of settings that schedules zero watering time?

Details on the zone settings
Area 20sq ft
Available water 0.17 in/in
Root depth 8"
Allowed depletion 50%
Efficiency 90%
Crop Coefficient (Dynamic) 82% today
Nozzle inches per hour 3.27

Double check your nozzle inches per hour. 3 inches per hour is a LOT of water. Since you said it’s a drip, that seems really high.

I calculated it using 0.7GPH (measured with a Moen Flo) and the flume from How do I calculate my precipitation rate?

(96.25*.7)/20.6 = 3.27in per hour

OK, so not scientific. I played with my drip emitters for a long time to figure out what worked appropriately. Some was math, and some was just watching what they did. My landscaped areas have mostly 1/2GPH emitters on them, and I ended up going with .2 inches per hour on them.

Play with your system a little bit and see how it reacts. I don’t know if Rachio’s inches are actually Cubic inches – if not, dividing your 3.27in/hour by 9 would bring you down to .3 or .4 inches per hour. That seems really in line with what I had to set up. I would try one of them and see how it responds.

You have your calculations wrong. Q is gallons per minute, and your Moen gave you gallons per hour.

Precipitation rate ( PR ) is a calculation of the flow rate (application rate) over the square footage of the zone. Let’s break down the equation:

PR = (96.25 * Q) / A

96.25 = constant that converts gallons per minute (GPM) to inches per hour. It is derived from 60 minutes per hour divided by 7.48 gallons per cubic foot, times 12 inches per foot.
Q = gallons per minute (GPM)
A = zone square footage (area in ft2)

(96.25*0.011667)/20.6 = .0545"/hr. Seems much closer to what I’d expect from a drip emitter system.

Another option is to check out the excel file that our own @azdavidr created years ago. Makes it REALLY easy!

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Sorry I didn’t check the FLO app carefully. It is showing me 0.7GPM.

I guess you never really mentioned it, but what type of irrigation do you have on this zone. I’m with @Linn and 3.27"/hr seems pretty high. I suppose if you have a mushroom bubbler or something, then that could be accurate.

I use a drip tube, 1/4” dia with pressure regulating drippers every 6”. I use a loop around the stem of each plant, so there’s probably about 15ft total at a guesstimate.

https://www.sprinklerwarehouse.com/catalogsearch/result/?q=ML-106B

Update: woke up early enough to catch a cycle. Even though the app shows 0 minutes, it does still water the zone. It was running for 40s on a zone that shows 0 minutes in the app.

I guess watch and see if that is putting down enough water. I’m still saying that something is off there, I just can’t quite wrap my head around what it is…

I guess the original issue is a UI issue. Using integers to show durations and seemingly always rounding down.

Moving on to my place, I think I’ve decided to close off all my drip manifolds and then turn on the valves. I’ll use the Moen Flo instant flow meter to pressure test the zones for subterranean leaks.

FWIW a couple of the other dripper zones do come in at 0.7~1.2"/hr. This zone being just 20sq ft means 0.7GPM is 3.27"/hr

OK, lets look at it a different way. Lets just assume you have 15’ total of this drip tube for 2 trees. That means 7.5’ per plant? This tube has emitters every 6", so there will be 15 emitters for each tree, pushing .52 gallons/hour each. So each tree is going to get 7.8 gallons per hour. If you flow sensor is picking up .7 gallons per minute, then you have a leak somewhere I think…

Now, if we plug that 7.8 gallons into the drip emitter calculator that @azdavidr created (using my systems figures - gallons of water to be applied and inches of water applied in a flex daily schedule), I come up with .47 in/hr. MUCH closer to what I would expect to see from micro drip irrigation. There is no way that the 1/4" emitter tubing you linked is going to supply enough water to those trees in a 1 minute watering.

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