In case anyone's confused:
You're supposed to plug the basin and run both facets to fill the basin to the desired height and temp and then use that mixed water for whatever purpose. Then you when you're done, you drain.
Why would you do that? Because:
You mixed those two buckets of water in a basin in your bedroom and then used that warm water to clean your face and pits everyday. You sure as shit didn't take a full bath or shower everyday, because that's a lot of fucking water to draw/pump form the well and then heat on the stove and that's hard work. So you bathed about once a week.
So later on some lazy faggot says he's going to run his water pump inside his house because he's getting real tired of your shit with the carrying heavy water into the house. Splendid idea. So you run the water into two main places: one to your basin next to your bed, and one above your stove so you can heat that shit. You will see this popular with old rich snooty ladies on TV that are house shopping and have loose flaps of bacon hanging under their jowls. "Horray! this kitchen has a pot filler!" No, you dumb hag, that's not there because cooking spaghetti is too fucking difficult, it's because that's where you would make hot water, traditionally.
Now, a little latter on some lazy bastard gets tired of carry hot water around the house from the kitchen, so he invents a water heater, (which was originally pretty much a large pot of water permanently sitting on a permanently burning stove) and plumbing to move that water around the house. Well, those new hot water pipes are just going to pour into the basin from the other side, using the exact same hardware that already exists because--fuck it--why invent something new? Washing your face in the basin still works well enough.
So that's what people did before mixer taps. Any fuck who claims double taps "are better" is obviously Thatcher-level autistic. If this was any other time in human history, society would make that fucker a pig farmer.