Irrigation 101

At most homes in Southern California, landscape irrigation accounts for 50 percent or more of total water use. Fine tuning your irrigation system can save tens of thousands of gallons of water annually.

Use the Most Efficient Sprinkler

The most efficient sprinkler is the one that delivers the highest percentage of water into the root zone of the plant. Here is the percentage most commonly used for each type of sprinkler. We’ll explain why below.

%

Drip

%

Rotary Nozzle

%

Rotor

%

Spray Nozzle

Drip Irrigation

Drip emitters water in gallons per hour, not gallons per minute. Because they water slowly, water does not build up on top of the soil and runoff or evaporate. And emitters are placed right in a plant’s root zone, reducing water waste even more. Drip irrigation, or soaker hoses, which water at the same rate, should be used on perennials, shrubs, groundcover and trees.

Rotors

Rotors shoot a single stream of water that moves slowly across the lawn or landscape. They cover a greater distance than other sprinklers and are usually used on larger properties. Rotors are less apt to cause runoff because the stream is moving and allows time for water to soak into the soil. Their larger droplets of water are less likely to blow off target in a breeze.

Rotary Nozzles

Rotary nozzles are more efficient than spray nozzles for watering a lawn. They release a larger water droplet into the air which is less apt to blow away in the wind. Rotary nozzles also apply water more slowly than spray nozzles, reducing the likelihood of runoff. To replace a spray nozzle, pull up on the stem, unscrew the nozzle, and screw on a rotary nozzle with the same spray pattern and distance (45, 90, 180 or 360 degrees). Aim the new nozzle and you’re done.

Spray Nozzles

Spray nozzles are the most commonly used sprinkler in home landscapes, and generally the oldest and most inefficient. They spray a fan of small water droplets that are more susceptible to wind and they apply water quickly, faster than most soils can absorb it, increasing the likelihood of runoff. Homeowners should replace spray nozzles on their lawns with rotary nozzles and spray nozzles in their planters with drip irrigation.

Schedule Irrigation Based on ET

Efficient irrigation is when you apply water at the same rate that a plant is losing water through evaporation from the soil (E) and transpiration from its leaves (T) – its ET rate. Water loss, and the need to irrigate, is higher on a hot day and lower on a cool day.  There are two ways to schedule your irrigation based on ET.

Use an Online Calculator

For each of the stations in your irrigation system, enter into the BeWaterWise Landscape Watering Calculator your zip code, the water use level of the plants, whether the soil is clayish, loamy or sandy, and the type of sprinkler. The calculator shows you how many minutes to water each week of the year.

Buy a Smart Controller

A smart irrigation controller automatically adjusts station run times based on ET and can save you water, time and money when compared to standard controllers.  The real value of a smart controller, of course, is that you do not need to remember to reprogram your controller each month. Rebates may be available.

Use the Cycle and Soak Option

Helix’s drought regulations limit irrigation to two days per week and no more than 10 minutes per station each day. But, how do you water for 10 minutes without water running off the landscape? The solution is to divide the 10 minutes into smaller cycles. There are two ways to do this.

Use Multiple Start Times
Some irrigation controllers offer multiple start times on the same day within one program, while other controllers require you to use multiple programs.

On Start Time 1 or Program A:
Schedule the same days and 3:00 minutes at 12:00am

On Start Time 2 or Program B:
Schedule the same days and 3:00 minutes at 2:30am

On Start Time 3 or Program C:
Schedule the same days and 4:00 minutes at 5:00am

Use the Cycle and Soak Option

The cycle and soak option on your controller will automatically divide your 10 minute watering cycle into smaller cycles, preventing runoff and allowing water to infiltrate into the soil before the next cycle begins.

Regulate Your Water Pressure

The numbers below are excerpted from a manufacturer’s performance chart for a spray nozzle. The optimal water pressure for a spray nozzle is 30 psi, but the numbers show how an increase in water pressure—to 40 psi—increases the nozzle’s flow rate by 0.04 gallons per minute.  That’s wasted water. It doesn’t sound like much, but it adds up quickly. Now consider that household water pressure can be up to 70 psi and higher.

Gallons wasted by one sprinkler in 10 minutes

Gallons wasted by 60 sprinklers in 10 minutes

Gallons wasted by 60 sprinklers in one year

Measure

Screw a water pressure gauge on to a hose bib and turn the water all the way on. If your pressure is higher than your sprinklers’ optimal pressure, you can save water by installing pressure regulators. Gauges are available at hardware and irrigation supply stores.

Ask

You can reduce water pressure with regulators that attach to valves, or with sprinklers and drip irrigation parts that have pressure regulators built in.  Ask the experts at an irrigation supply store what is best for you and how to install it.

Install

Installing pressure regulators on your irrigation valves does not involve the digging needed to install pressure regulating sprinklers. Note, too, that manufacturers have how-to videos and  installation guides on their website.

Two More Water Saving Tips

Try Deficit Irrigation

Optimal irrigation is providing the water a plant needs for growth, maximum quality and best appearance. Deficit irrigation is providing just enough water for adequate appearance and little or no growth, and is an option to consider during drought. Reduce your watering times by 20 percent, monitor your plants and provide more water if needed.

Install Check Valves

Check valves prevent water from draining out of the lowest sprinklers in your irrigation system, after the station turns off. Check to see if this is happening. If it is, install sprinklers with built-in check valves.

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