[BusNit]

I do not think my coach ever had the sight glass since the ports on the black tank have blank-outs and no threads. (Just flat white melted in circular blanks from new) I do have the flush port and have used it although it's doubtful it will clean much. Now it could be possible someone replaced the tank? There was evidence of toilet paper shreds stuck all over the place in the wetbay from some kind of explosion!