The RP-500 Backflow Preventer is designed to supply maximum protection against back flow caused by negative pressure or backpressure. Often required by regional councils to protect contamination of water source. Any backflow may cause infiltration of chemicals, fertilizers and/or other pollutants into potable water systems. The RP-500 is reliable and easily maintained, without the need for special tools. The RP-500 is built with two independent, easily replaceable capsulated spring-loaded check valves. A revolutionary, internal Reduced Pressure Zone, located between the check valves, ensures protection and reliable performance of the relief valve. filtration bore headwork stream river pump extraction irrigation frost protection sprinkler drip stock nursery greenhouse apple kiwifruit blueberry citrus vegetation matter screen seperator pond liner pump water irrigation filter sand iron oxide pipe pressure