Flomatic Valves presents the RPZE and DCVE, unleaded bronze backflow preventers that are designed to protect drinking water from lead contamination and are constructed to comply with the federal and state laws in California. The unleaded material - Enviro Check - has a maximum of 0.05 percent lead content, a tensile strength of 30,000 psi and a yield strength of 17,000 psi. The unleaded backflow preventers come in a variety of sizes and configurations, from 0.5 inches to 8 inches. Flomatic Valves. Card No. 9