In-ground irrigation systems, or automatic sprinkler systems, have gained popularity as water resource management has become an issue in our rapidly expanding exurbs. In addition to using native grasses and using mulch rather than chemical fertilizer, these systems can conserve water and keep lawns green through the summer without having to get up in the morning to turn it on and remembering to turn it off before it floats the tulips down the driveway. Installing one of these systems is fairly easy if you plan your strategy carefully. Follow these steps.
Items you will need
Sprinkler spray heads and rotors
Pipe and fittings for supply lines
Saw or cutting tool for pipe
Shovels or trench tools
Hand tools (screwdrivers, wrenches) specified by installation instructions
Work gloves and safety glasses
Make a plan. If you don't have professional help, map out your yard's "zones" considering soil types, planting materials, weather conditions and any "microclimate" considerations like sun, shade and adjoining surfaces that may affect how much water is needed. Lay out zones of areas with similar requirements because, although you may be able to program each zone, you can't alter water flow within a zone. You must design a system that your water service will support. Keep in mind that a supply to the system must maintain a specific water pressure (which varies according to the size and complexity of the system) in order to pop those little heads up to sprinkle. Consult an irrigation contractor if necessary to install a supply line for your system.
Lay out the system before picking up a shovel, checking to make sure that you haven't forgotten obstructions like trees and fences. Dry-fitting will help check your math. Use parts made by one company since different companies make parts that are not necessarily compatible. Read directions that come with the controller, valves and sprinklers, so that if you have questions, you can check online or with your supplier before everyone has gone home. When installing a water supply for your irrigation system, be sure to add a back flow preventer to keep water from the sprinklers from flowing back into the household water supply. Your system will need to maintain a water pressure of 35 to 45 lbs. per square inch (psi) water pressure to operate properly.
Mount the controller in a convenient place inside at about eye height so it will be easy to program. Drop a line to the valve box. Line this box with gravel underneath the valves to keep dirt out of valves and connections, and to make repairs easier and less frequent. Connect the main lines for each zone to the appropriate valve. Dig trenches for main line and laterals, putting your lines down and installing fittings for sprinklers as you go. If you live in an area where winters are cold, you'll want to install traps and waste vents to drain the system in the fall.
Install sprinkler heads. Be sure to put filter screens in spray heads and rotor sprayers to keep impurities from clogging the water channels. Install one zone at a time, including end and waste traps and checking pressure as you go. If heads are slow to pop up, pressure is too low and if the sprayer mists, pressure is too high. Pressure regulators at the beginning of the system can correct these problems. Pressure regulators can be installed on the water supply to boost pressure to the system or on individual zones to boost or lower pressure for zones that are large, small or too far away from the source.
Install and test the complete system before back-filling. Line the trenches with a friable material like sand or pea gravel to provide drainage and protect from freeze-thaw cycles.
Know your yard's "micro climate," including any areas subject to "wind tunnels" near adjoining buildings. Use larger capacity sprinkler heads to treat raised areas or areas that dry out faster than others and aim your sprinklers to use the wind not have to spray in its face.
Surround sprinkler spray heads with turf removed during trenching to keep dirt from clogging openings or getting in the pop-up mechanisms.
Program your in-ground irrigation system to water in the early morning hours just before and after sunrise when the winds are calm. Watering in the evening or cool of the night encourages growth of fungus and mildew and most water that is applied during daylight hours evaporates rather than sinking in.
Mow your grass higher in sunny areas to shade roots--their water demands will be closer to the level used by shady spots.
Installation is the easy part of this project--it's the design that is an advanced activity. One design does not work in every situation, so it is wise to consult a professional if you have any doubts about your own planning skills.