Installed transfer pump to move gray water into black water tank. Used a 12Ø volt, Little Giant magnetic drive pump because it was free and has no seals to leak. I put a “T” in the 1½” ABS gray water drain line with a reducer bushing to ½” FNPT. I then drilled and tapped a ½” NPT in the black water vent stack and screwed in a plastic poly flow adaptor with glue. All lines are ½” poly flow tubing. Installed a single gang handy box in service compartment with switch and one outlet for pump. (6/Ø3)