North Texas has clay soils, slab foundations, a “monsoon” season in the spring, and extreme heat in the summer. This combination leads to expanding soils that quickly retract in the summer, causing foundation settling. Preventative measures involve drip lines around the foundation to keep the soil moist and applying pressure to the foundation year round, holding the foundation in place. Unfortunately, Rachio’s advanced settings are a bit confusing when it comes to drip lines, so I thought I’d share how I set my settings to get a working flex schedule.
The installation and recommended schedule:
The crew that installed the lines used 0.4 GPH, 18" emitter spacing check valve drip lines. They buried 12-18" off the foundation at 4-6" depth. The recommended schedule they provided is twice daily 22 min per drip line, reducing the days you water in the cooler months. They provided a 4’ T rod to push into the soil so you can gauge whether you’re watering too much (gurgles when you pull up) or too little (no soil stuck to the rod).
The Zone Settings:
Spray Head: I set to rotary nozzle to allow for flow measurements. It shouldn’t matter otherwise
Soil type: In most cases where you’ll use these foundation lines, clay will be right but I’d set what you have. The guide listed here can help!
Exposure: I set to mostly shade
Slope: Shouldn’t matter
Area: I measured the length of the hose and multiplied by 3 feet, assuming the drip line would be equally wetting 18" to either side of the line.
Available Water: Set to my soil’s available water, 0.12, determined using the guide at the link above.
Root Depth: I set to 5", assuming I always wanted the soil above the drip line to be moist and the water will work its way down under the foundation over time regardless.
Allowed Depletion: We want the soil to stay moist so this should be pretty low. I have mine set to 5.5% but played with it to get my schedule watering time right.
Efficiency: I set to 100%. Since the lines are buried, all the water is making it to the soil.
Crop Coefficient: I set this to 20%, as low as it could go. We don’t have any plants perspiring that would drive it up and most of our water isn’t making it to the surface to evaporate. It would be handy if we could lower it further but Rachio hard limits us at 20% minimum, unfortunately.
Nozzle Inches per Hour: We can’t use catch cups for underground drip lines so we need to go about this a bit differently than you would for your lawn. I measured the drip zones using my city water meter in cubic feet per minute and converted to cubic inches per hour of water. Convert the square footage you found above to square inches. Divide your cubic inches of water per hour by your square inches and you’ll have the inches per hour for your zone.
Tweaking the Zone Settings to Hit the Schedule:
I created two flex monthly schedules and aimed to hit ~22 minutes run time for my zone on each schedule. Allowed Depletion was adjusted until the duration was correct and Crop Coefficient was tweaked until January scheduled dates were about once or twice a week. This link here tells you how adjusting the parameters effects your schedule.. I set one flex schedule to run in the morning and the other in the evening and turned off wind skips for both.
Hopefully this helps someone else with their foundation watering needs!