Very common problem in Jabsco toilets
made in the last 6-7 years. The wet/dry "valve" is actually just a little gate (they call it a cam) that the lever swings to block or unblock the flow of flush water. Due to either a tooling or mfr'g defect, that little gate tends to hang up in the dry mode. The cure: a new wet/dry valve assembly, which is NOT a part included in the service kit. You can see the drawing for your toilet here: http://www.jabsco.com/prodInfo/overview/29090-2000_ev.pdfJabsco hasn't gone of out business, just moved their customer service to a new location. They did that several years years ago, so your toilet can't be very new. Jabsco toilets are so flimsily built that they aren't worth putting ANY money into...they're "disposable" toilets. You can often find 'em on sale for $99...the service kit is about $60. You can easily spend $400-500 over several years in an effort to keep a $100 working.My advice: replace it. Your best "bang for the buck" in a manual toilet is the Raritan PH II (or the PHC, which is the same pump on a compact base, to fit in tighter space)...about $250...rated the best toilet under $500 for decades. Keep it well lubricated, rebuild it every 5-6 years, and it'll give you at least 20 years of trouble-free service. Quite a few people here have PH II toilets and love 'em. YOu can read all about here: http://www.raritaneng.com/products/toilets/manual/ph_2.html