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Drip isn’t always more efficient

Proper scheduling and maintenance are musts to help drip irrigation use less water — not more.

The ongoing drought has been rough on many landscapes. And while some in-ground sprinkler systems are working overtime, drip irrigation has been working double-and triple-time — and using far more water than traditional irrigation systems.

Under current Stage 2 watering rules, drip can be used eight hours a day, every day of the week. While this is allowed, it doesn’t mean it’s necessary. So, it’s time for a change.

SAWS has proposed an update to San Antonio’s conservation ordinance that would limit drip irrigation to one day a week on the designated watering day like other irrigation, to prevent excessive water waste.

Many drip systems are scheduled to water multiple days a week and often apply far more water than plants need, harming rather than helping them. But with the use of drip growing in San Antonio, at many sites it’s using just as much water as the inefficient irrigation it replaced.

Drip is often sold on the basis that it’s efficient, which can be true but is not an absolute. Drip can apply water directly to the roots right where plants need it, resulting in less evaporation.

But if it’s designed or maintained poorly — particularly when it’s set to run more often than necessary — it can be much less efficient than traditional irrigation methods.

Consider these examples.

  • Mike has a grass lawn. He has a spray zone that delivers 2 inches of water per hour. There are nine sprinkler heads that use 9 gallons of water per minute combined. It’s set to run one day a week per stage 2 rules for 20 minutes. Mike’s spray zone uses 180 gallons of water each week.
  • Janice has long garden beds with native perennials around the edge of her yard. The beds contain a custom point-source drip system with .9 gallons/hour emitters that apply water only where there are plants (not on the blank mulched spaces in between). There are a total of 100 emitters across the beds that use 0.75 gallons per minute combined. She has it set to run once a week for 45 minutes. Janice’s point-source drip zone uses 70 gallons of water each week, and she checks the lines every week to make sure nothing is broken.
  • Tony has converted the lawn to a large garden bed with one drip zone with 12-inch grid- spacing and emitters delivering 0.9 gallon/hour. It applies 1.44 inches of water per hour, comparable to a heavy rainstorm. In total, it contains 400 tiny emitters that use 6 gallons per minute combined. A system using water that quickly should only need to run 21 minutes per week. But Tony schedules it to run three times a week for 40 minutes each (which is allowed under current Stage 2 rules). Tony’s grid drip zone uses 720 gallons of water every week (even more if there’s a broken line).

It’s easy to see that drip is complicated and scheduling it can be confusing. So, what if you already have drip?

  • Keep an eye on it! “Set it and forget it” does not apply to drip. Make a habit of walking your drip lines when they’re operating. Watch and listen for the sound of spraying water — on a drip line this is invariably the sign of an issue. If so, find where it’s coming from.
  • Fix it. Breaks in drip tubing are commonly caused by landscapers, mowers, string trimmers, and visiting animals who relish chewing the wet plastic. These leaks immediately negate its distribution efficiency until you or a licensed irrigator repair it.
  • Schedule an irrigation consultation. Unsure of your settings? SAWS has licensed irrigation experts on staff who can visit your property to evaluate your irrigation system, identify any leaks or problems, and help you reschedule your system for optimal efficiency, as well as Stage 2 compliance.

The proposed changes to drip rules under the city’s conservation ordinance are meant to rein in drip and signal that it, too, is intended to be a tool for water conservation — not water waste. (A drip variance is proposed to allow additional watering for vegetable gardens.)

SAWS has ended its own irrigation rebates for drip conversions, though other irrigation rebates and efficiency upgrades are still available.

Going forward, a period of community discussion has begun. In the coming months, the SAWS Board of Trustees and San Antonio City Council will consider acting on changes to the existing watering rules.

Your opinion matters — we want to hear what you think at wateringrules.com.

Learn more about the proposed updates during a webinar hosted by Karen Guz, vice president of Conservation, Thursday, Sept. 28. Register now to join the discussion.

Brad Wier
Brad Wier
Brad Wier is a SAWS conservation planner. Years in South Texas landscaping and public horticulture gave him a lasting enthusiasm for native plants that don’t die when sprinklers -- and gardeners -- break down. He’d rather save time and water for kayaking and tubing. He is a former kilt model, and hears hummingbirds.
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