The reason I asked about power, is that in the pics you will see the shower that was added to the shed, lean-to, with sawdust toilet in the "bathroom".
Started as a "Zodi" in a bucket, then a 12v pump in the "pulpit" (55 gal plastic tank in the pulpit to keep from turning green), then the second 55 agl drum (painted blue to keep from turning green), Water from the roof.
Then to a 12 v "sprayer pump" that has a presser switch. Shut off the sprayer the pump stops.
Finially added a 2-1/2 gal elect water heater in the shed, turn the t-stat all the way down( no mixing valve) ran the 12v pump thru the heater.
Heats up in about 15 min, gives 2-1/2 gal shower ( longer if you want, but only so much hot water).
Have the cabin done now but the shower is still there, for after working in the fields.