Watering a rooftop garden presents unique challenges -- you can't just connect a sprinkler to a hose and let it run. But it's possible to create a drip-irrigation system for plants growing a long way above the street. James Murez, manager of the Venice Farmers Market, has set up a customer-tailored drip-irrigation system for his rooftop garden. It's designed to meet the needs of individual plants and containers so the surface of the roof remains dry. The system is on an automatic timer. Because the plants have varying watering requirements, emitters with different flow rates are used to control the delivery of water. Although the whole system may be activated for 1 or 2 hours at a time, each plant receives a precise amount of water, according to its needs. The colors of the emitters indicate their various flow rates (figure A). An attachment connected to the system is used to apply fertilizer in specific amounts. The system is made from a variety of hoses, tubes, filters and emitters that can be snapped together in various ways. A hole-punch tool allows the user to snap adapter fittings onto the tubing (figure B). Emitter heads are placed where needed along the tube. Once the system is in place, end fittings shut off the flow of water. The drip system attaches to an outdoor faucet or water source. If the system is attached to a faucet, a back-flow preventer must be installed to protect the water supply, then a pressure reducer and a filter to remove particles in the water. Emitters are rated in gallons per hour, indicating how much water each delivers to a plant in an hour. Mist heads and in-line emitters may be used for container plants that are set up in rows. Impact heads work like miniature versions of large sprinklers.
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