I'm in Adelaide too, and like you concerned and make an effort to save water.
I am just doing film at the moment, 135, 120 and 4x5 format. I develop in a rolling drum with motor...I like it because I can develop without shaking the damn tank, and I can roll for a long time at low temps around 13 degrees C. I used to hate the stress of exact number of inversions x exact time x exact temperature. That used to always get me uneven negs. Now I do it all with a cup of coffee watching the roller do the work.
So I wash in the roller too. First lot of water (300 ml) roll for about a minute, tip out. Next lot 5 mins (300ml) tip out, next lot again just 300ml roll for 5-10 mins, tip out. Take tank off roller and add demin water+photoflow, smooth of any bubbles. Let soak for couple mins. Lift out negs...usually couple rolls of 120, or 4 sheets of 4x5, and hang. I use a car wiper rubber to get the water off so they dry faster. I reuse the final water+photoflow a couple of times before discarding. I get perfect even negs which don't go brown with hypo stain.
Advantages...very little water used, and a final rinse in demin water (from the supermarket) avoids the problem of Adelaide's very salty town water.
Rollers and large diam plastic tanks can easily be made. I got an electric old roller from eBay for $50. It's really a dream not having to do the rattle n' roll by hand.