2019 Cobia 262 Livewell

[STAPE]

Any idea what type of female threaded pipe is inside the livewell (where the fill elbow screws in)?  Would like to add a shutoff valve in its place to prevent water from coming in when not in use.  I know the seacock valve can be closed but that will also eliminate raw water and render washdown useless.  There is only one seacock valve on the raw water supply line.