Putty or a silicone type sealant is normal for the tank outlet fitting with a hose clamp. IF there is a hose clamp, then the odds are the tank is NOT a ABS outlet. ABS is hard and a hose clamp will not tighten that plastic. I use a product called SikaFlex and can be purchased at Lowes and Home Depot. Much better than caulk or silicone for these type seals. Doug
If the unit used a hose clamp, then the odds are the tank is NOT ABS and the ABS cement would not adhere to the 2 different plastics, so you did the right thing by not gluing it.