[VAC] Blue Holding Tank

[Ray Plumlee <hrp41@xxxxxxxxx>]

Does anyone out there have any ideas on telling how "full" one of those
blue, wheeled holding tanks is before it gets "too full" - i don't have
any holding tanks on my 55 a/s and planned to use a blue tank for
brown/gray water when no hookup is available - after all the recent
posts to the list about holding tanks i got to thinking about how to
avoid creating myself one helluva mess by overfilling one of those
things then having to "unhook" it to install the cap for transport -
the more i sit here and think about this i'm beginning to think that i
came up with a pretty "crappy" solution - any "flashes of brillance"
about this would surely be appreciated -  Ray P