This is a pretty neat product for home owner irrigation. I use a couple of tools that measure volumetric water content like the Acclima product, but one is handheld the other is in the soil. The products I use take the guess work out of when to water. Basically your looking for a percentage of volumetric water content that is just before the point that your turf will start to show drought stress. A lot of people use 15 to 20% volumetric water content as the point at which they water. However this number depends on a lot of factors, type of soil, type of turf, height of cut, health of turf, time of year. I would think in the dry west you would want to volumetric water(VMC) content slightly higher, say 25%. Now is the the time to play around with your system I would set the tolerances low, maybe 15%. Watch to see if your lawn starts to wilt at 15%, if it does then set the tolerance to 20% if your lawn wilts at 20% go to 25%. Good luck this system, used correctly it will save you a lot of water.

Here is a link that might be useful: Acclima irrigation.