Section 11-21-7 - Irrigation systems(a) The following guidelines relating to backflow prevention devices for irrigation systems shall apply: (1) Atmospheric vacuum breakers shall be installed after the last control valve of each sprinkler circuit and at a minimum of six inches above the highest irrigation head. The atmospheric vacuum breaker shall be installed only on irrigation circuits with heads that will not return any pressure in the circuit when the circuit control valve is closed.(2) Pressure vacuum breakers shall be installed at the beginning of each irrigation circuit and at a minimum of twelve inches above the highest irrigation head on the circuit. Individual irrigation circuits having quick coupling valves or other similar type heads that will permit pressure to be retained in the circuit shall have a pressure vacuum breaker installed as a minimum requirement for each circuit. Irrigation systems using the subsurface drip method shall have a pressure vacuum breaker on each circuit. A pressure vacuum breaker may not be installed where a double check valve assembly, reduced pressure principle backflow prevention device, or air gap separation is required.(3) A double check valve assembly may be installed to serve multiple irrigation circuits in lieu of vacuum breakers on each individual irrigation circuit.(4) A reduced pressure principal backflow preventor or air gap separation shall be required before any piping network in which fertilizers, pesticides and other chemicals or toxic contaminants are injected or siphoned into the irrigation system.[Eff. 12/26/81] (Auth: HRS §§ 340E-2, 340E-9) (Imp: HRS §§ 340E-2, 340E-9)