For me too the sound of water constantly running in the darkroom, I admit I've run my share of water down the drain. Where I live we have a mix of water meters and no water meters, anyone applying for a building or remodeling permit is first sent to the water department to get metered. I don't have a meter but wasting a lot of water isn't right. I contacted Hass manufacturing and got nice reply from Bill Hass. I asked if the water could be turned off when not needed as opposed to my Kodak unit which has to run to be tempered. He said the unit stabilizes in 3 to 5 seconds. It would be close to tempered water on demand.
Another thing I keep hearing is the need for shorter wash times with new films and the use of TF-4 fixer. I don't wash 120 film like I used to but give it multiple changes of water and not water constantly flowing over it.