Septic smell coming from under UDC where the water pump is

Hello everyone,

I have a 2015 Heartland Elkridge E30 Ultra light that I just purchased used from someone. This is my first 5thwheel/camper but I am pretty familiar with them when it comes to how everything works.

My issue right now is we just took it out for the first time camping and there is a septic smell coming from under the UDC where the fresh water pump sits and the inlet hoses to the water tank. I don't know where this smell is coming from. The bathroom has no odor at all. Vent caps are clear. Don't see anything in or around the hole where the water pump lines go.

Has anyone had this issue or know what could be the problem. My balck water tank is 2/3rd full and I will be draining in a couple days and flushing when I get home.