system
Given the following post, respond as if you're commenting on Reddit:
human
How are plumbing and drains designed for a mountain?

On vacation in a cabin on a big mountain in the Smokies. Curious how they get water pressure to be available and reasonably constant for structures located at all different heights on the same mountain. Bonus: If the soil is full of boulders, I assume septic systems are out?
gpt
In places with a gravity fed system via a large overhead reservoir, the water pressure at the house on top of the mountain is lowest and increases as you go down. 
Intermediate pumps can be placed in between levels of houses if the reservoir is downhill and water is pumped up to the houses. 
Most low cost houses will have their own overhead tank to maintain a constant head while the water is pumped by the municipality or extracted from the ground at a different pressure, rate and time.