We cleaned the water tank on our 54 shortly after purchase. We know Amel did not build all boats the same but I cannot believe they would make a significant change such as going from one to three tanks. To verify open the port you show in front of the galley refrigerator and get rough dimensions on the tank, convert to cubic feet, then to gallons - 1 cu ft equals 7.48 gallons. The tank extends forward and aft under the chest refrig/freezer & galley refrig. We have one tank on this boat. Removing the under seat freezer would be difficult (understatement). -- Mark Mueller Brass Ring A54
