Use this page to download the 07 Que brochure:
http://www.sunlineclub.com/brochures.html
Page 4 lists the water capacities: 13 gal. black, 25 gal. grey, etc.
I'm not familiar with the Que so I'm sure someone else will help out too. The bigger Sunlines have a control panel on the wall with indicator lights for battery and tanks. If you don't have that, the best you can do is look down the toilet while flushing; if you can see water it's time to dump. For 2 people, 13 gal. black water will last you 2 days, 3 at the most.
Henry
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