This is a point I was thinking of while reading this thread.
Originally Posted by RPC
Most (note, "most") developers are more innocuous than many of the household things people put down drains. Stop bath? Was someone really serious in including stop bath? Would you put salad dressing down the drain? If you would, then stop bath is even safer - the fats in the oil in the dressing are more likely to clog your pipes, and the vinegar is about the same concentration as stop bath.
Fixer, yeah, I'd recover or at least remove the silver ion too before pour it into a septic system, but there are ways to do that like the silver magnet to recover it, and it's even easier if you don't want it in recoverable form (steel wool or aluminum foil.)