The Zurn Wilkins 475STRV Stainless Steel Replacement n-Pattern Reduced Pressure Principle Vertical Assembly (RPV) withstands the corrosive effects of water and allows for installation in systems when inlet and outlet flows up. Â Ideal for new or direct drop-in replacement delivering convenience without compromise. For fire protection applications , with a metered by-pass to detect leaks and other water use. The patented AR spool provides a replacement for Zurn Model 475RPDAV Ductile Iron n-Pattern, as well as unique customer-modified installations.