Interesting house that only has one sink.
If for some reason my kitchen sink was out of order and I couldn't immediately fix it I would use one of the others. They really do get their water from the same source. Yes, you can drink the water from the bathroom sink or even the tap outside the house.
You're forgetting the mindset of the primitives, sir.
I first noticed this with the cooking and baking primitives.
Primitives can't grasp the concept that something can have more than one use.
The typical cooking and baking primitive, for example, has one 2-quart pot for boiling peas, another 2-quart pot for boiling corn, a third 2-quart pot for boiling rice, a fourth 2-quart pot for boiling beans, a fifth 2-quart pot for boiling eggs, a sixth 2-quart pot for boiling potatoes, a seventh 2-quart pot for boiling gravy, and so on.
It just doesn't occur to the primitives that a pot can have more than one use.
And this would be even a further stretch, a primitive figuring out that he can wash the dishes in any place other than the kitchen sink.
Imagination and adaptation are too far beyond the primitive mind to grasp.