Such a mundane but essential thing. You probably had a shower recently, you probably didn’t even think about it much until you read this.
How long were you in the shower?
How long did it take to get get clean and how long was just being a little self indulgent?
How much water do you think you used?
Consider yourself in a water and water heating limited situation.
How fast could you get yourself clean and what’s the least amount of water you could use?
Could you do it in 2 minutes?
Could you do it with less than 20 /10/ 5 liters of water?
What are you going to do with all the black(?) water you just created?
Have you tested your own home made soaps?