regarding the legalities of dumping chemicals down the drain with silver or heavy metal content DON'T DO IT no matter what the laws in your, city/ town/province/state/country say.
Three years ago I was visited by Toronto Chemical Management officers. They showed up unannounced with their testing devices and demanded to sample the waste BEHIND the flow of the Silver Recovery at the point where the hoses entered the floor drain leaving our building.
I was very proud of the fact that Elevator passed the examination with flying colours. The penalty would have been an immediate shut down of my operation until I was able to comply. This would have meant temporary financial disaster for our company.
I urge all home darkroom users where ever you are located , to consider the risks associated with dumping spent fix. You local plumber has absolutely no idea the implications as well as your local community leaders. Even small usage is no excuse for dumping, and for those who think it is ok , I would suggest rethinking this practice and do not move to Toronto.
We are offering workshops off site that require Jobo processing, included in our kit for making this possible are 2- 50 litre containers to capture spend dev, stop , and fix, which we bring back to Toronto to go in our SRU.
I have two dogs and I practice safe poop and scoop/disposal, which I think in some locals this policy would be silly but to that point I make sure we put fixer through a device that removes the heavy metal before it drains into the City's system.
If the laws become tougher and there are devices that will turn my spent chems into pure water, I can assure you I will do my best to do so.
PRACTICE SAFE DUMPING even if you are not legally bound to do so.