I have not ever had this happen but 2 things come to mind. The first is the by-pass valve used when you winterize your coach, Try in in the bypass position and see if your flow improves. You will not get any hot water. If you have good flow reposition the valve for normal use. If the valve appears to be OK than my next guess would be a failed check valve on the input or output of the water heater. I have seen some posts in the Winnebago Forum about failed check valves. Perhaps if you did a search in the Winnebago Forum you may find some info there. Good luck and report back the solution to your problem. We all learn from each other and that is what makes iRV2 such a valuable resource.
Don & Bev Morgan Weyauwega WI, 05 Itasca Horizon 40KD, 400 HP Cummins, Adopted by a great couple, Toad 07 Saturn Vue AWD, Air Force One, TST 510 TPMS, Mayor of Weyauwega 2007 - 2013, Waupaca Co Board Supervisor 2010 - 2014