Use just 1 gallon to wash dishes = 1
I just don't see how. I have far too many disgusting dishes to pull that off.
Yeah, I thought about using 3 gallons for that number. But here is how -- Assuming one person.
Breakfast -- two eggs - Rinse plate immediately for 1 second. Rub scrub sponge around plate with a dab of soap. Rinse 3 seconds. You could soak it all day as I do.
Dinner - Using the same nonstick deep pan still there from breakfast. I merely ran a paper towel around it and added olive oil. (no water needed) 1 chicken breast, stir fry veggies (same pan), boiled 1/2 gallon water in non stick pan for rice.
Clean up -- discard anything in trash from plates and pan using paper towels that were used for dinner. Use hot water from rice pot to soak pan and plate with a little soap while I relax. 1 hour later gently rub pan, pot and plate, fork, knife. with sponge. Rinse for 9 seconds. (.45 gallons)
Total gallons = 1. If you have 2,3,4 people you could actually do this more efficiently by stacking the dishes in 2 inches of the soapy rice water.
YMMV
(why is there water left over from rice? I use the French method. put some hot water (5 or 6 times the rice volumn) in a pot. boil rice 10 minutes. strain rice in colander. comes out perfect every time. In my case I discard the rice water as I'm on a well and don't give a hoot. But the rice water is hot and perfect for rinsing/soaking if you care to trouble.