The Apollo™ air gap drain (AGD4A) is designed to funnel minor discharges from a reduced pressure backflow preventer's relief valve due to line pressure fluctuations and/or minor check valve fouling, into the drainage system. Drain piping is easily attached to the AGD4A's threaded bottom outlet and have the additional option of using the outlet OD to glue on a coupling using the appropriate cement or the use of a flexible pipe coupling.