Let’s get your model figured out. You said it’s a Minnie Winnie Plus 28RSS? There is no such model. There is a Minnie Plus 28RSS, it’s a 5th wheel. See, a Minnie Winnie Would be a Class C motorhome. Lots of Minnie owners put the world “Winnie” in their model name and it gets things confused.
If you have a 5th Wheel towable then you will need to contact Winnebago and ask them to email you a PDF of your plumbing diagram. Only Winnebago motorhomes have online resources like you’re looking for.
Also, I t is always helpful to mention your model year along with the correct model name.
2017 Winnebago Adventurer 37F
2016 Lincoln MKX Toad