Clack Retention Tank Problem

The inlet port on my retention tank is causing my plastic c-clip to come off when I screw in the pipe connection, thus allowing water to spray back out. Anyone ever have the issue and/or know what might cause it? The pipe connection screws in fine on the outlet side.

Does your tank have the by-pass valves or plain adapters? At any rate you may want to try screwing the pipe into the adapter and then install the adapter and c clip. If that don't work then something is f'd up (technical term) and you probably need to replace the inlet adapter assembly. And remember, it's plastic so don't gorilla the fittings in