This blog has been updated since its original post.
A huge source of water waste lies buried in yards across California and the U.S.: the pop-up sprinklers many homeowners use to irrigate turf grass. Now California's investor-owned energy utilities, led by Pacific Gas & Electric, are proposing new standards for spray sprinkler bodies that could save jaw-dropping amounts of tap water, as well as the energy to pump and treat it.
About half of California's total urban water use occurs outdoors, which is why a state-commissioned report last year aimed its recommendations at slashing landscape use of potable water in half from pre-drought levels. And while the state's most recent drought crisis has receded, the imperative to conserve water resources has not. "The drought emergency is over, but the next drought could be around the corner," Governor Jerry Brown said in April. "Conservation must remain a way of life."
Spray sprinkler bodies tend to fly under the radar—most people probably couldn't name or describe them—yet they're ubiquitous. A sprinkler body is essentially the underground housing for a pop-up sprinkler in an automatic landscape irrigation system. Spray sprinklers are the predominant form of irrigation for residential turf grass, and the useful life of a sprinkler body is a bit less than 10 years. The utilities estimate that over 18 million spray sprinkler bodies are sold every year in California alone, and most of them could be operating far more efficiently.
The standard proposed in September to state regulators at the California Energy Commission would require these products to maintain the sprinkler manufacturer's recommended water pressure, which is most commonly 30 pounds per square inch. That's less than half the average pressure found in water utility service pipes across California, as documented by my colleague Susan Lee here. Operating a sprinkler above its rated water pressure contributes to misting, wind drift, evaporation, and overspray within and beyond the landscaped area—all forms of water waste that will be curtailed by pressure regulation.
The proposed standard would also require spray sprinkler bodies to contain a check valve to prevent water in the irrigation piping from draining out through the lowest sprinklers in a sloped landscape after the system has been shut off.
Taken together, these requirements are estimated to reduce residential spray sprinkler water use by about 20 percent and save a stunning 248,000 acre-feet of water per year statewide, once the installed stock of spray sprinkler bodies fully turns over in 2028. Nearly all of these savings are in the form of treated drinking water, and for comparison, this volume is more than all the water currently used by San Diego, the state’s second-largest city. The present value of these savings to California consumers is estimated at $5.6 billion.
The new rules wouldn't require a heavy lift for manufacturers. All the major sprinkler companies already have products that would meet the standards, but they are currently niche products, with an estimated 10 percent share of the market. Given the product's relatively short lifetime, a transition to the more efficient versions would happen naturally over the next decade as they're replaced.
UPDATE: The Environmental Protection Agency's WaterSense Program—a voluntary water efficiency program President Trump proposed to eliminate in his 2018 budget—has recently finalized a similar specification for sprinkler bodies to earn the WaterSense label. In response to public comments from NRDC and others, EPA clarified and strengthened its initial draft. As published, the new WaterSense specification lacks a requirement to include a check valve to prevent low point drainage, but it calls for pressure regulation (which is where the lion's share of water savings are obtained) with a bit more stringent metric than the standard proposed in California. (California's final rule could incorporate this provision as well.) Importantly, the test procedures that will be used to certify compliance with the California standard and the WaterSense specification appear to be compatible, allowing one test to qualify products under both state and EPA criteria, which is a major benefit to manufacturers.
The EPA estimates that consumers would see a modest increase in price for these products, but would recoup such costs in less than two and a half years. For California’s proposed standard, the estimated payback is even shorter—about 15 months.
California's mandatory standard, together with the specification for the WaterSense label, are likely to influence the market nationwide, and help accelerate the move toward more efficient irrigation. Standards for irrigation controllers—the mechanisms that set watering schedules and shut sprinklers off when it rains—are also in the works at the California Energy Commission, and will achieve additional savings of water and energy. But the bulk of the water savings for residential irrigation will come from the uncontroversial, common-sense changes to spray sprinkler bodies proposed in September.
With new home construction back on the upswing and more automatic sprinkler systems being installed across the state, now is the time for California to adopt this obscure but important standard. And with California’s water managers continuing to debate the location, timing, environmental impacts, and need for expensive new sources of water, these large water savings can’t come a day too soon.