Byron,

As pointed out, the tank drains better when at least 2/3rd full. (Don't forget the appropriate rv chemicals).

On our '97 Safari, there seems to be a little "slack" in the indications on the grey/black guages. Generally speaking, the guages read somewhere between 5-10 gals high. When I was a boy back in the olden days, the guage for the black water tank in my folks '62 Bambi consisted of one eyeball, a flashlight and the open flapper on the toilet.

I don't know how the arrangement on your Bambi is, but on the Safari if you open the flapper on the commode (turning the supply valve to the toilet helps here) and look down, there is a straight down drop to a slanted surface into the BW tank. When the liquid is just visible on the slanted surface, there is about 5-8 gallons of capacity left. (This I determined by the water addition method). Our tanks are the 30 gal. variety.

I hope this gives you an alternate idea for monitoring tank capacity. Also, the more experienced 'streamers suggest avoiding towing full BW & GW tanks and leaving with full water tanks. Various reasons include: 1.You don't know when your tanks will be emptied at the rally: 2. Reduces weight: 3. You have not a clue when the water will be hooked up. Which all make sense.

I am glad things are moving along for you.

Jerry KJ4IT