Arrived at location and found air gap to backflow dry and backflow not weeping / discharging water. Water pressure at this time on the inlet side was 80psi and outlet side building pressure was 70. Model of PRV is 500XL Wilkins. With pressure creeping up above set point, manufacturer recommends cleaning and or rebuilding. Kit number for rebuild is RK212-500XL. Went down to the lower building to see if that backflow is having issues. This system does not have a PRV installed, static water pressure is 76psi and no signs of discharging from relief.