Dividing an irrigation system into zones can reduce the flow requirement of the irrigation system and reduce the size and cost of the pump used to operate the system. A zone is a section of the irrigation system where the valves, piping system, and spray heads are operated at the same time.
To insure even distribution of wastewater, a single zone must have the same sprinkler heads with the same precipitation rate throughout. Matched precipitation heads are recommended to ensure that wastewater is evenly applied to avoid ponding and surface runoff. Matched precipitation means that sprinkler heads apply the same depth of water regardless of the spray pattern. This can be accomplished by selecting the proper sprinkler head or by swapping the sprinkler nozzle (see Step 5). If a full circle spray head puts out 4 gpm, the 180º spray head should put out 2 gpm and the 90º spray head should put out 1 gpm. All of these spray heads can be located in the same zone and still provide even coverage of the application area.
Zones are created using valves. For wastewater irrigation, electrically actuated diaphragm valves are used. While a variety of manual valves exist and may be appropriate for traditional irrigation systems, they will not work in wastewater applications where water must be irrigated at the same rate that it is generated. The programmable control unit will determine when the valves open and close by sending a 24-volt signal creating a magnetic field that moves a small metal plunger inside the valve.
Diaphragm valves are available as either normally open (NO) or normally closed (NC) models. In NC models, the valve is closed whenever a signal is not being received from the controller. The NC valve is preferred in wastewater irrigation systems to ensure that wastewater is not sprayed during a malfunction of the controller or wiring network.
Selecting the proper size diaphragm valve is essential for the valve to operate correctly. Each model has a minimum flow rate. It is important to consult the manufacturer’s specifications and select a valve that works well at the designed flow rate.
Number of zones created: 2
Valves selected: 3/4 inch 24 volt plastic globe valve with manual shutoff
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