Avoid cut-off or rigid nipple connections. Swing-pipe assemblies should be a minimum of 6 inches long to provide flexibility and a maximum of 18 inches long to avoid high velocities and friction losses. The swing pipe is a support device, not piping for the irrigation system installation.
Install zone valves in a valve box of ample size. This lets you service the valve without having to remove the valve box. You should install a valve box on a crushed stone base to help the box drain and to support the box. The valve box should be set to proper grade. When possible, set valve boxes in a landscaped area where they can be hidden in mulch.
The electric valve needs to have two wires connected to it to operate. The control or power wire is an independent wire installed from the controller to the valve. The other wire is a common wire that is installed from the controller to all the valves. The common and control wires should be different colors to tell them apart. For new installations, common wire is usually white. For renovation projects, yellow is a good common-wire color. Splice and connect wires using waterproof connectors to ensure long life and to prevent corrosion or shorting out of the connection due to moisture.
Install wire connectors in the valve box with the valve and color code the wire. Small wires such as multi-strand #18 AWG have individual colored wires for each valve. On larger systems using #14 AWG wire, the common wire should be one color, turf areas another, landscaped areas a third and extra wires a fourth. This makes troubleshooting and repair easier.
Place controllers in a location convenient for the operator and near 120-volt electrical power. Install the controller so that the display is at eye level. Putting the controller in a convenient location-a garage or the entrance to a house-makes it easier to schedule changes based on weather and seasons. Inconveniently placed controllers encourage a "set it and forget it" attitude.
Controllers installed outside should have internal transformers. Install outdoor controllers in weatherproof enclosures. The controller manufacturer or a third-party vendor can provide enclosures. Any above-ground wire leading to the controllers should be installed in conduit. Power supplies for outdoor controllers should use GFI breakers. Program the controllers for proper operation of the system, and keep in mind the different precipitation rates of the various sprinklers.
The installing contractor needs to train the owner to properly operate the irrigation system and controller. In most cases, lack of training results in over-watering. Proper training should include a discussion on controller operation, precipitation rates, maintenance requirements and how to shut off the water in an emergency.
A properly designed and installed irrigation system will result in a water-efficient system that will last for many years. Selecting appropriate equipment and following industry standards are important aspects of every irrigation system design and installation. There needs to be only one weak link for the irrigation system to break down. Planning is a must, and you must follow through with your design intent during equipment selection and installation.
Brian E. Vinchesi is a design engineer with Irrigation Consulting, Inc., in Pepperell, Mass., and Huntersville, N.C. He is the president of the American Society of Irrigation Consultants anda past member of the Irrigation Association Certification Board and Board of Directors.
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