I have a cabin on a remote lake in central British Columbia, Canada.
No power, though we have propane lighting in the cabin, and a combination wood/propane stove for cooking and heating.
For our shower, we use those Solar Shower bags. They work great!
Too great, if you leave them in the Sun too long. Then, you have to cool the shower water with a bit of cold lake water.
Same principle as yours, but yours is a much larger scale.
I'm still thinking of getting a metal garbage can, putting an H-shaped propane burner from a barbecue under it, and heating water that way. Also thinking of making the H-shaped burner quickly removable, inside a larger barrel that can double as a firebox.
We have a separate water tower for gravity fed water to the sink. Gas pump fills the 40-gallon tank directly from the lake. We drink straight from the lake. Everyone does. Never had a problem with purity.
Yours looks like a great system.
It's amazing how quickly water will heat in a black container. Met a family camping years ago that had a black plastic 5-gallon bucket they'd fill with water, then hoist up over a limb with block and tackle. This gave them hot water for washing dishes and hands. A length of garden hose led to the little table they used.
Good system. Not so good in the morning, after it's cooled at night. Perhaps an insulated jacket around the bucket after sundown would have saved some of the warmth for morning. I don't know.
One thing people tend to forget, though: water is very heavy. A gallon of water weighs about 8 pounds.
You fill a 55-gallon drum with water, and you've got 440 pounds to wrestle with. That's why we used a 40-gallon tank in our water tower. Filling directly from the lake is easy, and 40 gallons lasts the two of us a few days.
And occasionally we get "protein" at the tap: a tiny freshwater shrimp!