holding tank help

[wlbsr]

Need to install a holding tank that will be used very little if any. My thoughts were to use a stock 3 or 5 gal todd or comparable rectangular tank with a 1 inch inlet for the hose coming from the y valve. I will also have a 1/2 or smaller inlet for the vent and an additional 1.5 - 2.0 inch inlet with a cap. My idea is to have some type of quick connect on the 1 inch waste line that would seal off both ends when disconnected (like hydrolic fittings). the vent line would be unscrewed and a cap screwed on. the whole tank could be taken out of the boat to a toilet, a 1.5-2.0 inch spout screwed on the inlet that had the cap, the vent cap uncrewed, and dumped. Once again, I plan to lock the bathroom within 3 miles and go overboard outside of 3 miles so the idea is this tank would probably only be used by accident and i would like a way to rinse it out and start fresh if it did happen to get used. Any general thoughts on this idea and ideas on a type of 1 inch quick connect fitting that would shut off both sides when disconnected? thanks for your help.