...De Niro and Stiller) is (are) having problems with, then?
The stuff can't be supposed to sit in that tank for ever either, can it? (What would you do when it gets full; buy another one just like it and bury it next to the old one...?) Naah, AFAIK, the guys with the big suction hose come and slurp it up into their tank every now and then. (Wasn't it them that[*] Crazy CIA Dad [De Niro] spent most of the second half of the first movie frantically calling for?)
Peridocal emptying... JUST like the tank(s) on your RV.
[*]: Originally, I had written "Weren't they whom...", and while I still think that's not actually gramatically *wrong*, it doesn't look quite right either.