Iowa Admin. Code r. 875-91.3
Where pressure-reducing valves are used, one or more relief or safety valves shall be provided on the low-pressure side of the reducing valve when the piping equipment on the low-pressure side does not meet the requirements for the full initial pressure. The relief or safety valves shall be located adjoining or as close as possible to the reducing valve. Proper protection shall be provided to prevent injury or damage caused by the escaping fluid from the discharge of relief or safety valves if vented to the atmosphere. The combined discharge capacity of the relief valves or safety valves shall be such that the pressure rating of the lowest pressure piping or equipment shall not be exceeded in case the reducing valve sticks open. If a bypass around the reducing valves is used, a safety valve is required on the low-pressure side and shall be of sufficient capacity to relieve all the fluid that can pass through the bypass without overpressuring the low-pressure side. A pressure gage shall be installed on the low-pressure side of a reducing valve.
Iowa Admin. Code r. 875-91.3