Normally once the month of July roll around the heat and dry weather starts to set in and the dry spots in the lawn with start to show. The question of how much I should run my irrigation comes up daily and there is not a simple answer.
The first thing to look at is if you have any water restrictions for your area. Most water districts in and around Austin are on once or twice per week watering. They typically will let you know the day you can water by your address number.
Second: Is your property on a slope or hill? The more of a slope that your lawn is on then the less amount of time you can run your system before the water starts to runoff and heads off down the street. The way to solve this is to split your runtimes into different start times. If station #1 needs to run for 20 minutes, but the water starts to runoff before that time you will need to set the controller to run two 10-minute runtimes. This will help the water soak into the soil. The best way to achieve this on the controller is to set multiple start times that will cycle through the entire system, then immediately start over and run through it again. Each controller is slightly different on how to set this up, but it is simple once you learn it.
Third: What type of irrigation system do you have? There are multiple layouts and varieties of nozzles, heads, and drip systems that will determine how long the runtimes will be. If you have the small spray heads, the runtime normally is under 15 minutes due to the amount of water they apply per minute. Rotors and MP type heads will run 20 to 60 minutes since they apply a small amount of water over a large area. You will need to know all the different types on your property since you generally will have a mixture of them.
Fourth: The soil type plays a large role in the amount of water needed. A sandy soil will not hold as much moisture as a clay base soil. The water requirements may not fit with your water restrictions and may have to tolerate some dry spots as we move through the hottest part of summer.
When watering we want to water deeply into the soil. The roots of your turf will chase the moisture down and with a deep healthy root system it can tolerate the heat much better than a shallow root system plant. This may be something that has to be monitored weekly to get the right balance and will need to be adjusted according to the season and current weather. You can’t just set the irrigation controller once and leave it. It needs to be adjusted seasonally and monitored for any issues.