Magically powered showers perhaps? But yeah, that confused me a little too when I was doing my first playthrough.
Magic showers 
I briefly looked into the plumbing situation of the wild west and saw that like even in major metropolitan areas indoor bathrooms with plumbing werenāt really a thing til like the 1920s. Itās something thatās a little handwavey I will say, but Iām also not really trying to entirely historically accurate anyway lol
Thereās just magic in those pipes somewhere
You could always just use the off-the-grid shower thatās practically just a bucket with a faucet and watering can head and works solely with gravity, although thatād still need a little plumbing for the water to go somewhere.