That looks like it could be a diaphragm pump at the back of the closet with the handle on it, where does that line terminate at the back of the closet?
Could be that the van had a different toilet installed at one point and that was used as a pump or flush out?
Where does the “Y” go to that’s behind the toilet? Anything under the van at that junction-Water tank? Grey water tank? Waste tank?
Could it be a manual water draw fill?
'03 Ford E350 7.3L Diesel
(de)SMB'd Custom RB-50
Quigley 4X4 w/Deavers & Agile Offroad's R.I.P. package
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