Ord 2011-006 - Laserfiche WebLink

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(f) Pressure type vacuum breaker or PTVB. This is an assembly containing a single loaded check valve and an air opening which admits air whenever the pressure within the body of the assembly is reduced so that there is a tendency toward back siphonage. The body of the assembly must be equipped with two tight closing shutoff valves, one immediately upstream from the body and one immediately downstream of the body, and two properly located test cocks. It must be designed to operate under pressure for long periods of time without becoming inoperative, making it possible to isolate a lawn sprinkler from the potable system. It must be installed so that it is never subject to backpressure. (g) Reduced pressure backflow prevention assembly or RIP. This is a device consisting of two independently acting approved check valves together with a hydraulically operating, mechanically independent pressure differential relief valve located between the check valves and below the first check valve. These units are located between two tightly closing resilient - seated shutoff valves and are fitted with properly located resilient seated test cocks. Reduced pressure detector backflow assembly or RPDA. This is a specially designed assembly composed of a line sized Reduced Pressure valve assembly with a bvpass containing a specific water meter and an approved Reduced Pressure valve assemblv. The meter in a RPDA must register in units of gallons per minute and must reizister accuratelv for only very low rates of flow (less than three Gallons per minute). It must also measure all rates of flow. This assemblv shall be used to protect against a • health hazard (i.e. contaminant). The RPDA is primarily used for private on -site fire systems. Sec. 86.592. Types of backflow prevention required. (a) The degree of protection and the type of protection deemed necessary to prevent backflow and possible contamination of the city water system are outlined in this section. Cross connections vary widely in degree of contamination hazard. Backflow may occur under many different pressure differentials, varying from vacuum to very high pressures. The protection afforded by a backflow prevention assembly depends upon its type, the circumstances in which it is installed, and on its proper installation, testing and maintenance. (b) Criteria for selection of backflow prevention assemblies. The selection of an appropriate backflow prevention assembly depends upon the degree of hazard involved and will be based on the following criteria: (1) Whether or not the assembly could ever be subject to backpressure due to the customer's internal pumping pressures or elevation differentials. C7 10