[wingnut60]

Last name I had for the old Trailertiresandwheels.com is "TrailerSetGo.com" and that is a valid tire/wheel website. Duane had the name of the original business in OH, but they sold/moved back to/toward Elkhart if I remember correctly. They were sure great in sending out tire/wheel packages if changing from 16" to 17.5" on the Doubletrees. Bet you can use Duanes info to find them.

As to working on the black tank valve--remove the water filter/housing, will be much easier to reach area behind. As shown in the pics, you can see the 3" black tank drain angling at 45d downward. Valve is just out of sight, can see it easily if remove the water filter. Not too hard to work on it, just tedious due to all the plumbing. If going to work on it, drain the tank and rinse it well--then raise trailer on the drive side to keep any fluid left inside the tank. Then it is just a matter of long arms, 4 bolts removal. On mine, when I pulled the bolts, the drain line dropped downward giving me room to work. One tip--use plumbers grease to hold the gaskets in place when replacing the valve, otherwise you might pinch them when sliding the valve body in place.