"Indirect" plumbing connections

[rfesk]

A floor drain (with trap) is the same as the drain from your sink if they both drain into the sewer system - just lower.

[Drew Wiley]

I certainly don't classify any darkroom effluent as "gray water" useful for watering plants outside. Pets can be affected, or perhaps yourself working in the garden. Maybe final relatively clean washing water from a slot washer or something like that could be reused. But anything with real chemical content would give me cause for alarm. If you want to make serious money, don't be a photographer, but a Vet who charges a thousand dollars for tests which still can't identify what is slowly killing your puppy or kitty.

I do toss out the daily water jacket tempering liquid around the fruit trees. But that's just plain water.

[willwilson]

The air gap for some commercial (mostly restaurants) between a drain and a floor drain is to break the vacuum. This prevents a drain backup from coming up in to your sink and contaminating the washing area. Same idea as a back flow preventer or air gap for a soap/chemical dispenser in foodservice. Sanitary sewer is sanitary sewer whether plumbed PVC or in to a floor drain with an air gap.

Chemicals down the drain sucks. It all goes back to a body of water (in TN where I live rivers/lakes ). That said, we photogs are not the problem. It's the big industrial users. Be nice to the planet though.