a few ideas
1. Collect the necessary water over time to minimize the impact on your water supply, and do larger batches, less frequently.
2. Depending on your workflow, washing aids or archival rinses can reduce the amount of water required for washing.
3. For manual tank developing of film, the Ilford wash method uses minimal water:
"fill the spiral tank with water at the
same temperature, +/ 5ºC (9ºF), as the
processing solutions and invert it five times. Drain
the water away and refill. Invert the tank ten times.
Once more drain the water away and refill.
Finally, invert the tank twenty times and drain the
water away."
It's not as convenient as leaving the water running and walking away, but it is effective, and overall faster.
4. Not many hobbyists use drums or tubes to process prints, but you may want to look into it as a way of conserving water and/or solutions (which are after all mostly water).
5. See #1 -- your biggest gains will likely come from workflow management: consider your options re methods and equipment, and organize your sessions and workflow to use water most efficiently. For example, consider one-shot chemistry vs mixing large batches that may expire before they are used up, or replenishable chemistry that can be revived for longer term use.
I use diafine to develop B&W negatives. Diafine working solution lasts forever and can be reused many times. I expect the two quarts I mixed up last month to be viable for at least a year. However, it is a peculiar developer that works differently than most, and it's not for everyone.
Previously, I used HC110, which does act like more common developers, but it is a long-lasting syrup that can be used one-shot, and I mixed up only as much as I needed when I needed it. There is a companion replenisher, as well.
Enjoy!