Black water tank

[Ranman68]

We just returned from a camping trip and had a question. Just out of curiosity, how big is the black water tank? We've got an '03 3023. We haven't been camping for more than a few days yet, but according to the gauge, the tank gets about half way full or a little fuller. Is the black water tank big enough to be able to open the lever on the toilet into the black water tank and then recharge the toilet, or is it a 1 time only deal?
I'm thinking when we go for a week, this may be an issue?
Thanks for your help.