Aalberts Integrated Piping products at The House Supplier include an air gap fitting for the RP4A reduced pressure backflow preventer in 1-1/4 to 1-1/2 inch sizes. The air gap directs relief valve discharge from the assembly into a drain without a direct connection.
Match the air gap to the exact backflow preventer model and size it serves, and confirm the drain line below it can handle the full relief discharge flow. Check local code and water purveyor requirements for backflow assembly installation, including clearances, test cock access and annual testing by a certified tester.
