I have this oval cutout on the right side plumbing bay. On the inside there are two clips that appear to have held something like a sight glass. Was there supposed to be such a thing? Can't find where it would have been tapped off the tank(s)
On my '93 there was a vinyl tube for a sight glass on the combined black/grey tank that clipped into that area. Are there hose connections at the top and bottom of your tank?
I disconnected the sight glass line and capped off the holes, seems like Newell worked real hard at making things easy for people and all you have to do is look at the tank and you can see the level, at least I can. Also my tank gauges above the microwave work perfect, just one of the few things that did in my coach.
Like Oliver and Jack said it was a sight guage for the waste tank. Mine still has it. In addition to being a sight guage mine also has a hose fitting plumbed into it for flushing the tank. I use it fairly often.
The tubing on mine has yellowed to the point that I can't see how full the tank is, bot I do like the wash out port.
My waste tank has ports in the top, left, and lower left front side when you open the inner water bay door.
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!
Mine is also dark gray. Kind of like a grey granite tone. Electronic level gauges still work. As I looked at it closely today, it may have been the tank repair that was noted on one of the receipts. They spent something like $2500 on that repair with their tech noting the removal of drilling out 50 or so rivets.
