Fresh water tank not totally draining
I have added a hatch to visually see my tank level with markings. I drained it to add fresh water for our trip tomorrow. For some unknown reason, the water level dropped to only my first marking which is 3.5 gallons. 3 days ago when I drained the tank it was empty visually. Could the drain be blocked by a piece plastic hole cutout for the filler, air vent or drain fittings?
I understand that all the water can't be drained out, but how do you folks that winterize deal with residual water left in the FW tank?
2004 Winnebago Minnie 22e(went to a nice family Oct 3, 2015)
2016 Forester 2701DS (Aug 31, 2015)
2017 Camping 12 trips 38 nights
2018 Camping 10 trips 38 nights
2019 Camping 6 trips 19 nights
2020 Camping 0 trips Cancellations 4