Section 7-10-02-02 - Allowable antisiphon devicesOne of the following antisiphon devices must be installed as required in this section before chemigation in an irrigation system may take place.
1.Check valve with vacuum relief and low pressure drain.A corrosion-resistant check valve must be located between the water supply pump discharge outlet at the point of chemical injection. Location on the suction side of the water pump is not allowed. The check valve must be either spring loaded with a chemically resistant sealing surface or otherwise capable of preventing leakage. The direction of flow must be clearly indicated on the outside of the device. The vacuum relief valve must be installed on top of the irrigation pipe on the inlet side of the check valve. The vacuum relief valve must be a minimum of three-fourths inch [19.05 millimeters] in diameter. The low pressure drain must be located on the inlet side of the check valve at the lowest point. The drain must be mounted in the pipe in such a way that any check valve leakage enters the drain rather than flowing on toward the water supply. The drain must be at least three-fourths inch [19.05 millimeters] in diameter with a closing pressure of at least one pound per square inch [7 kilopascals] and not exceeding five pounds per square inch [35 kilopascals]. If the drain is within twenty feet [6.10 meters] of the water source, the system must provide a means to carry the drainage away or the surface must be graded to assure drainage away from the water source. Manual valves may not be located on the outlet side of the drain.2.Reduced pressure principle device.The reduced pressure principle device must consist of two independently acting check valves, together with a pressure differential relief valve that is located between the two check valves. This device must be located between the pump discharge outlet and the point of chemical injection. The differential relief valve must have a minimum clearance of twelve inches [30.50 centimeters] above the ground level or grade.3.Double check valve.The double check valve assembly must be composed of two single, independently acting check valves. The double check valve must be located between the pump discharge outlet and the point of chemical injection.4.Airgap.An airgap must be a physical separation between the free flowing discharge end of a water pipeline and an open or nonpressurized receiving vessel. To have an acceptable airgap, the end of the discharge pipe must be located a distance of at least twice the diameter of the pipe above the topmost rim of the receiving vessel. In no case can this distance be less than one inch [2.54 centimeters]. The airgap must be located between the pump discharge outlet and the point of chemical injection.5.Other acceptable devices.Other equipment utilizing new technology or other backflow prevention devices as specifically approved in writing by the commissioner of agriculture may be used.N.D. Admin Code 7-10-02-02
Effective October 1, 1988.General Authority: NDCC 4-35.1-03
Law Implemented: NDCC 4-35.1-02, 4-35.1-03