Operating Principles of a Reduced Pressure Principle Backflow Prevention Device Assembly Out of the Box or Dewatered
If there is no water in the RPZ (out of the box), the first and second check valves are closed tight and the relief valve is open. The springs in the first and second check valves are closing the check valves and the spring in the relief valve is keeping the relief valve open. The springs in the check valves are designed and installed to provide proper operation of the RPZ and to close drip tight when there is a small amount of debris on the seat or disk.