I have the same concerns and have been developing film and printing. I think the above advice sounds reasonable, and I notice Dan is putting first rinse into his silver magnet, so he's erring at about the same level of caution that I am. Here's what I'm doing: HC-110 ( I use 1-shot ) and Dektol go into a jug after use. For film, I've been reusing the stop bath but when I use plain water as stop ( for Adox CHS 50 ) it also goes into the jug. When I'm through with the stop it will go into the jug. Fixer also reused and into a different jug when it's used up. For film I'm using Illford wash ( but extended: 10-20-40 inversions, then two good soaks, then a soak in photoflo ) the first 2 go into the jug. For paper I do a long first wash and it goes into the jug. After that I let the wash water go down the sink into the septic.

This subject has come up previously here and I intend to follow good advice from PE and buy resitual hypo and residual silver test kits and actually test to see if I can detect any silver at the point where I'm allowing it to go into the septic or residual hypo on the film after my wash method. I doubt I'll be able to because the dilution ought to be great at that point.

What to do with the jugs is an interesting question. I'm using 5 quart containers that I buy the oil for my truck in. All that's in the main ones is used developer, stop, and rinse water. I seem to be averaging about 10 quarts per month. I think it will be okay to take those to a place where they can go through the municipal sewer treatment. The used up fixer is separate and I will take that to the hazardous waste disposal site once it is full. I asked around and there is no way to recycle it any more in my area.

Anyway, that's what I'm doing and I don't know for certain if it's okay, but it seems like a fairly prudent and cautious approach. We've been on our septic for 12 years with no problems ( I've had it pumped once, as a matter of course and not for any specific reason. ) I just started developing a few months ago so there hasn't been enough time to notice a problem if it's wrong. I'm thinking about using a microbe enhancer just in case some extremely tiny amount of silver is getting in there and causing any problems, but that might be a good idea anyway and can't hurt. I think that my volume could easily go up to 20 quarts per month, now that I'm printing more and also I've started using dektol at 1:4, but really it's that first wash water that is the largest volume for both paper and film. I make an attempt to really drain all the fixer for both film and paper before it goes into the water bath, so the total amount of fixer with dissolved silver is what sticks to the paper or film. For paper, I've been using batches of 250ml and it's not noticeable that the level in the bottle goes down before the fixer is exhausted, so the amount of carry over must be very small, and by the time it gets to second wash it must be very dilute.

Good luck and have fun!!