Also directly below the fresh water tank you should see a blue pex tube sticking out of the black poly sheeting. This will be the fresh water tank drain, it to should have a cap on it just as should the two low point (red & blue) pex tube drains. I installed shut off valves on all of mine to make things easier. I hope this helps.
Scott & Julie
2017 Sunset Trail 250RB
2015 F150 Supercrew w/3.5L EcoBoost/Max tow, w/
157” wheel base.