Are you sure? Sounds like you are looking at the Grey water tank drain not fresh water. Not sure about yours but some have more than 1 grey tank. Regardless, remove the 4 bolts around the flange of the valve and slide the valve out. This will allow you some room to work on the piping. Remove the piping fitting etc back to where the leak is, clean everything real good and re-glue check with your RV supply store for the correct glue probably Black Drisco pipe glue but better to check and be sure so you only do this once.
Also Welcome to the forum from mid California
Dale & Terri, Lulu & Tiki (our Chihuahua's), New rescue puppy Prince - Pom/Pug mix.
2013 Tundra, Double Cab, 5.7, TRD Off-Road, 4X4, Full Tow Package
2013 Wildwood T26TBSS - Sold
2000 Gulf Stream Sun Voyager M-8357 MH, Ford Trident V10 Gasser, 35 foot.