Sprinkler Systems Behaving Badly

Brad Wier

Notice your in-ground sprinklers running unexpectedly? They may be set to water twice a day — effectively doubling your water bill. Luckily there’s an easy fix.

It’s late summer and you’re following all the current watering restrictions. The sprinklers are running only one day a week with the seasonal adjustment at 100 percent to make up for the lack of August rainfall. Your scheduled watering is at peak efficiency and you’re using as little water as possible. Or are you?

Unfortunately, you may be watering 200 percent — even with the seasonal adjust set to 100. How is this possible?

There are two common, yet surprising explanations.

  1. Your sprinklers are set to run morning and evening. While this is a common practice in August, it’s an easy way to take a week’s worth of lawn watering and double it.

    Here’s why: a 20-minute cycle applies at least a half-inch of water on the grass, which is the typical expectation for turfgrass in south central Texas. While running the cycle again later that same evening is allowed under watering restrictions, it’s not necessary.

    If there are landscape beds or shaded areas of the yard, the temperature alone isn’t enough to increase their water needs. Instead of setting the entire irrigation system to run at 7 a.m. and 7 p.m., set it to run only in the morning. In the evening manually run valves in areas that still need more. You could also adjust the run time on the zone that needs it, typically the front-yard grass — adding five minutes for sprays, 10 minutes for rotors.

    This helps avoid doubling a 2,000-gallon sprinkler system and keeps you in control of any additional watering.

  1. Know your controller. Your seasonal adjust may in fact be set to 200 percent. On Rainbird SSTs (pdf) and ESP-RZXs (pdf), the seasonal adjust can range anywhere from -90 percent to +100 percent; the normal base setting is actually zero, not 100 percent as on many controllers. Always check your owner’s manual and watch the screen carefully when adjusting the seasonal percentage. If you see a big plus (+), you’re adding additional time to your intended irrigation cycle. This is a subtle technical detail, but it has big implications when the water is running.

    On a Rainbird SST or an RZX, if your sprinklers are set to 20 minutes, adding +100 percent will run them for 40 minutes, probably not what you’re trying to do (unless you want to double your water bill.)

If you see your sprinklers behaving oddly or running unexpectedly, consider it a red flag to pull out the owner’s manual and remember to check the programming.

For more information on saving water in the landscape, call 210-704-SAVE to schedule a free no-contact irrigation consultation.

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