Started to fill up my fresh water tank and noticed water dripping from under bottom of trailer. I went inside to check the tank under bunk bed and saw a water leak. It is coming from a hose about 5 in. long that has a plastic knob on it about the diameter of a silver dollar. It looks like a strainer in the center of this knob looking thing and this is where it it leaking. It is beside the drain hose for the water tank. Anyone know what this is and why it would be leaking?