3725 Water Pump

[JandC]

Has anyone with a 3725 done anything with their fresh water pump? We always use direct water hook up but I have been adding a little to the fresh water tank so that we can use the toilet when traveling during the day. The last several days I put in about 10 gallons or so and by the end of the day (one or two flushes) the pump is sucking air. We always turn pump off when not in immediate use. I unscrewed drain under back of Montana yesterday and sure enough tank only had about a gallon of water in it. I can't see anywhere it seems to be leaking out. Where is the fresh water pump located?