Design and Installing Lawn Irrigation Not As Easy As It Looks

Q. We installed a lawn 18 months ago, but it has a difficult time during summer months. I aerate it, fertilize it and I know the drainage is good because the landscaper installed the system to our HOA requirements. I water twice daily, six days a week around 5 AM and 9 PM. There is a decent amount of shade and the yard faces south. Even the heavily shaded areas have problems. What can I do differently?

Brown patches in lawns during hot summers will quickly show irrigation weaknesses. Notice these patches are also close to the patio where people walk. This area should probably be core aerified annually due to traffic.

A. I looked at your pictures and the lawn looks good in most places except for a few small brown areas. Brown spots during summer months frequently point out weaknesses in the irrigation system. In your case the brown spots are also in front of the patio where there is alot of human traffic. Areas like this should be core aerified annually.

Hollow tine aerifier

            My first suspicion is the irrigation system and was not installed or maintained properly. Let’s cover the basic “must dos” when installing and maintaining an irrigation system.

Water pressure

The operating water pressure MUST be within the operating range of the sprinkler nozzles. Frequently this is 15– 30 psi. Some expensive sprinkler heads have built in pressure regulators, but lesser expensive ones may not. If the water pressure is too high, fogging or misting will occur out of the nozzle. If the sprinkler head is “fogging”, then brown spots will occur in weak areas. If pressure is too high, reduce it with a pressure regulator. If water pressure is too low, remove any pressure regulator, change it for the proper one or install a booster pump to increase the water pressure.

Head to head coverage

Water must be thrown from the nozzle far enough to reach neighboring sprinkler heads. Sprinkler heads must be installed at distances specified by the nozzles. These distances are meaningless if you don’t have the right water pressure.

Sprinkler nozzles

Sprinkler nozzles specify the operating pressure range, allowable spacing between sprinkler heads and precipitation rate in inches per hour among other things. These nozzles must be matched to each other. If someone maintains the irrigation system and replaces a nozzle with the wrong kind, it will produce brown spots in underwatered, weak areas.

            Curved areas and re-curved areas of the lawn are the most difficult to water. There are adjustable nozzles that can be used but it will always be a weak irrigation area subject to brown spots.

•             Never water early at night like at 9 PM. If your lawn is healthy and it has a good irrigation system, one irrigation per day during summer is all that most lawns need IF the sprinkler system was designed and installed correctly. Irrigation should finish just before dawn. If you must water late in the day, apply water so that the grass leaf blades dry before it gets dark.
•             Don’t rake or catch the grass clippings when mowing. Most mowers now are “mulching mowers” with a special blade and deck design. Returning the clippings to the lawn substitutes for one fertilizer application each season.