AWWA C511-17 pdf download.Reduced-Pressure Principle Backflow Prevention Assembly
Sec. 1.1 Scope
This standard describes the reduced-pressure principle backAow prevention assembly for potable water applications. The assembly shall be capable of with- standing a working water pressure of at least 150 psi (1,034 kPa) without damage to working parts or impairment of function and for operation on hot- or cold-water lines.
This standard describes hot- and cold -water reduced-pressure principle back- Alow prevention assemblies. Assemblies shall be designed to operate, at a minimum, at a temperature range of 33°F to 140°F (1°C to 60°C). Hot-water assemblies shall be designed to operate, at a minimum, in water at a temperature range of 33°F to 180°F (1°C to 82°C).
A complete asembly consists ofa mechanical, independently operating, hydrau- lically dependent relief valve located between two independendly operating, inter- nally loaded check valves that are located between two tightly closing resilient-seated shutoff valves with four properly placed resilient-seated test cocks (see Sec. 4.3.1.3).
4.1.1 Dissimilar metals. In the presence : of an electrolyte, direct contact between metals of dissimilar corrosion resistance may result in galvanic corrosion of the more active, less corrosion-resistant material. When dissimilar metals must be used for internal parts, the rate of corrosion shall be reduced as much as practi- cal through the selection of materials that exhibit similar resistance to corrosion, or by placing a diclecric material between the metals, or by applying a dielectric coating. When contact between dissimilar metals cannot be avoided, the assembly shall be designed so that the resulting corrosion will be minimized and will not adversely affect water quality or result in malfunctioning or premature failure of the assembly.
4.1.2 Protective coatings. Ferrous bodies and parts shall be coated with a polymerized coating. The protective coating shall be composed of materials refer- enced in ANSI/AWWA C550 as deemed acceptable in the Food and Drug Admin- istration (FDA) Document, Title 21, Food and Drugs, Code of Federal Regulations, Sec. 175.300. The manufacturer shall provide documentation verifying compli- ance with this document or NSF/ANSI 61 when requested.AWWA C511-17 pdf download.