While Rachio can be a great irrigation controller when set up properly, most of them in the Austin area are set up incorrectly (although that is true for most irrigation controllers), and will cause significant underwatering of the lawn. The main culprits are Rachio’s incorrect default precipitation rates, and smart watering features which often don’t work with once a week watering restrictions.
Precipitation Rates
When you select turf nozzle for your zone in Rachio application, Rachio assigns it a precipitation rate which they claim is based on industry averages, but is in most cases incorrect (even for nozzles they recommend).
The correct precipitation rate requires either a cup test or an accurate irrigation plan, but lacking that, at least you can enter more reasonable values compared to Rachio defaults.
Rotary Nozzle - Rachio’s default is 0.7 in/hour, but most rotary nozzles installed in the last few years in the Austin area are Hunter MP Rotators with 0.4 in/hour in the most common configuration. RainBird rotary nozzles are generally 0.6 in/hour. If you are not sure what type of nozzle you have, 0.4 in/hour is a more reasonable choice.
Rotor Head - Rachio’s default is 1.0 in/hour, which is again much higher than most installed rotor heads, which are in most cases either RainBird 5000 (0.4 in/hour) or Hunter PGP (0.4 in/hour). Again, 0.4 in/hour is a more reasonable default choice.
Fixed Spray Head - Rachio’s default is 1.5 in/hour, which is pretty reasonable, although both Hunter and RainBird spray nozzles are generally around 1.6 in/hour.
You can change precipitation rate in advanced settings for each zone in your Rachio app.
Smart Watering Features
For this section, we assume that Rachio’s evapotranspiration calculations are correct, and assume you are allowed to water once a day per week, for 12 hours (which is the case for most properties in the Austin area). In the Austin area, most irrigation zones with warm season grasses (Bermuda, Zoysia, St. Augustine) should run for 154 minutes/week during summer (fixed spray zones should run a quarter of that) - there is no way to achieve this with only a 12 hour irrigation window, so the task of your irrigation controller changes from saving water to maximizing the water usage in a well distributed way across the zones.
Spring and Fall - we are still getting some rainfall, and evapotranspiration is still not at its maximum, so we recommend enabling all of Rachio’s Weather Intelligence features, but changing the Rain Skip threshold to 1” (this can be done from “Edit Home” menu).
Summer (Jun/Jul/Aug) - we recommend disabling all of Weather Intelligence features. This means your irrigation will run both during high wind, and during active rain event which is suboptimal for water conservation, but your only choices are to play by rules your water company gave you (and use every second of those 12 hours), pay the fines for breaking the rules (and possibly even conserve some water if you are watering during optimal periods), or re-sod your lawn every Spring (or potentially install drip irrigation, or switch to xeriscaping).
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