You cannot waste water - it will always flow to the sea unless evaporated into the atmosphere. What you can do is send it through your darkroom before it makes its way. A five minute rinse in the Jobo tank and then in distilled water with a wetting agent for roll films. Equivalent for sheet films in their trays. Prints: fill the bathtub one third and put your prints in. Shuffle them from time to time. I do this over a couple of hours -- but I don't hang around the bathroom -- just check in and shuffle from time to time. I've fiber based prints made over 20 years ago and they've held up just fine.