Mr. Drain Universal Water Softener Air Gap Drain For 1 1/2&uml; or 2&uml; standpipes Fits 1 1/2 or 2 standpipes. Unit housing length approx. 5 1/2 (13.97 cm). Can be mounted at 3 different levels. Designed to allow soft rubber washer hose or washer metal drain hook to share standpipe with the Air Gap unit. Inlet port fits 1/2 SCH 40 PVC slip fittings or our special couplings. Recommended usage 1 to 7 G.P.M.(3.7 to 26.5 Liters/minute) Tested at 15 G.P.M (56.8 Liters/minute) in lab tests.