Unfortunately, we still have people agitated by this. It’s an inexpensive, easy-to-use, safety, back-up system for special circumstances.
Gray tanks fill much faster than black, so black to gray movement can be minimized.
In our case, we generated a ton of dirty dishes and got full one day too soon…at 7:00 PM, and 5 min of effort the problem was solved.
This would also be handy to extend your time by a few days if camping without a sewer hook up.
And a backup system in case a “permanent” valve screws up.
Planning and common sense kept ours in the storage bay for 20 years. Planning and common sense provided an excellent, easy solution when plans changed. It’s also a viable option for week-long; sewer-less trips.
It’s now been 7 days and the gray tank still hasn’t disintegrated :)