We have a 2015 Minnie 22R. Most all RVs have a low level drain. One on the hot and one on the cold water lines. Plus there's a drain for the fresh water tank. Location of these will vary according the model. As pointed out above the water system diagram should show where these are located. It's a good document to have as a reference. Same for the electrical system.
Part of winterizing is open those drains. From there it depends how the system was winterized. Some people only use these drains, others will blow compressed air through the system, I think most will pump RV antifreeze through the system. You did not say how it was done.
It is possible that the hot and/or cold drains was left open over the winter. Thus accounting for your observation. Make sure you know where all the drains are located and they are closed.
Report back what you find.
Fred & Denise (RVM157) New Mexico
2007 Excel Classic 30RSO & 2015 Mini Winnie 22R
2007 RAM 3500, Diesel, 6Spd Auto, SWD, 4x4, CC & LB