Avoid: 11 common Irrigation Errors

The following issues are usually easy and inexpensive to fix; however, it’s always better to avoid them in the first place when installing a new system. If you already have an automated irrigation system installed and noticed one or more of these issues, you should definitely fix them. You can save 10% to 50% of your current irrigation costs.

1. Don’t mix different types of irrigation heads (rotors, sprays, bubblers, drip etc.) in the same zone, running at the same time.

The difference in application rate of the various types of irrigation heads, measured in inches per hour (IPH), is big enough to cause problems. Rotor heads typically have a rate between 0.10 and 0.25 IPH, while spray heads  usually run between 1.35 and 2.15 IPH. Bubblers have an application rate between 2.50 and 20.00 IPH and drip systems typically run between 0.25 and 1.50 IPH.

Mixing lower IPH heads in a zone with higher IPH heads ultimately means your system needs to run longer to avoid creating dry spots, which wastes water and money. For example, putting a rotor head in the zone with all spray heads creates a dry spot near the rotor head.

2. Don’t use the same run time settings on different types of irrigation heads.

Since the application rate for each type of irrigation head is different, some heads will require shorter run times, while others require longer run times; the higher the IPH, the shorter the run time. Determine the amount of water, in inches, that should be applied per week for healthy landscapes in your area. If you don’t know this number, your local county extension service can help you. Then, take that number and divide it by the IPH of the heads in that zone. You can find this by looking at the manufacturer specifications for your system.

After you’ve divided the amount of water, in inches, required by the IPH of the heads, multiply that number by 60. The resulting number is the total minutes per week that particular irrigation zone needs to run. Next, divide that number by the number of days per week you want your system to run to find your daily run time.

For example, 0.20 IPH divided by 1 inch a week = 5, then take 5 times 60 = 300 minutes. If you want to run the zone four days/week, divide 300 by 4 = 75 minutes/day. Then set your daily run times based on your site, soil, seasonal evaporation and transpiration rates, etc.

3. Don’t install spray and rotor irrigation heads too far apart.

Your system must have head-to-head coverage, which means that each head should overlap every other head. For example, if the manufacturer says the maximum throwing distance for a given nozzle at your working pressure is 10 feet, then 10 feet is the maximum distance you can put between heads in that zone. If you extend beyond that distance, you will have gaps in your irrigation causing dry spots and uneven plant growth.

4. Don’t adjust or reduce the throwing distance of any spray or rotor nozzle by more than 25 percent of the manufacturer’s (Hunter, Toro, Rain Bird, etc.) published/established throwing distance.

If you do this, you void the warranty on your system. Additionally, this adjustment results in uneven application of water which wastes water and costs money.

5. Don’t mismatch rotors with different application rates within the same zone.

System manufacturers (Hunter, Toro, Rain Bird, etc.) make rotor heads with differing gallon per minute (GPM) nozzles. It’s a mistake to assume that every rotor head in the same zone would have the same GPM. You’ll experience water savings of 10% to 40% by proportionally matching the application rates of your rotor nozzles. For example, if you have a rotor nozzle that only covers a 1/3 circle, you should have a nozzle that applies roughly 1/3 of the GPM that a nozzle in a full-circle rotor applies.

6. Don’t install incorrect spray nozzle patterns in zones using spray irrigation.

Make sure the spray pattern and distance of your spray nozzles are correct for the area you’re watering. If they’re not, you’re spending more money in one year than it would take to replace the spray nozzle and body.

7. Don’t include shrubs and flowerbeds in the same programmable zone as your lawn.

Trees, shrubs, and groundcovers have very different root systems than the grass in your lawn. Essentially, they live quite well on roughly half the amount of water your lawn needs. Always put shrubs and flowerbeds on their own programs in your controller.

8. Don’t allow overspray with spray and rotor nozzles.

If your irrigation heads are throwing water outside of your landscaped area, such as on to your neighbor’s property, sidewalks or driveways, change your spray and rotor heads from full-circle to half circle heads. One full-circle head, improperly installed, wastes as much water per year as the average spa tub.

9. Avoid installing spray and rotor heads on PVC vertical risers  within 6 feet of high traffic areas.

You may save a small amount of money by installing spray and rotor heads on risers next to sidewalks, driveways, pools, backyard play areas, and so on. However, this creates a huge legal liability if someone should fall on or trip over a riser and injure themselves.

10. Don’t waste water by running your irrigation system in the rain.

You can install rain shutoff devices on your system for little expense. These devices shut off your irrigation system during periods of rain, or after a certain amount of rainfall. Typically, rain shutoff devices pay for themselves in about a year.

11. Don’t run your automated irrigation system during the wrong part of the day.

Avoid running your system during the daylight hours. Wind patterns during the day interfere with proper watering, causing over-spray in some areas and dry spots in others. Additionally, due to higher water evaporation rates during the day, most of the water you apply doesn’t have enough time to get into the root zone and your plants don’t benefit from it. Nighttime watering presents a different problem; wet plants during the night are more likely to develop fungal problems, diseases, or freeze.
The best time to irrigate your landscape is in the early morning hours. You’ll avoid wind interference, excessive evaporation, and plant loss due to fungal issues, disease, and freezing.