OK, I didn't do this today, I did it a while back but it might save someone else from the same problem and there is an added benefit.
I added a slide valve on the dump manifold. Why? well seems that the way the valves are laid out, when I pulled out the electric cord it looped up and pulled the Black water valve. Thankfully the cap was on and had a good seal. So after getting back to the starting point by emptying the pipe between the valve and the cap, I added a simple twist on slide valve as a safety. I also added a 45 degree clear section so I can monitor how clean the tank flow really is. Not a biggie, but it could save someone a really messy time.
Now the extra bonus. When dumping the tanks I have a slightly modified routine. Dump the black, close the outer or safety valve and then open the grey, it flushes up into the black tank, as the levels equalize, close the grey tank valve and open the outer valve, repeat the process until the tanks are empty. I was greatly surprised at the amount of additional 'black' I got out doing this.
Really a simple and inexpensive project that made a big difference.
2016 Tiffin Allegro Red 38QBA
2008 Jeep Liberty (aka FireToad)