You are the only one in a public sauna. After finishing, you leave the empty water bucket in the steam room. You are being inconsiderate.
If you take the bucket out and leave it next to the faucet, you are not being particularly considerate, but I wouldn’t call you inconsiderate either. At least the next person can see the bucket and fill it up before going in.
When you refill the bucket and leave it ready for the next person who uses the sauna, you are being considerate. Bravo!
For those unfamiliar with the Finnish sauna, there is always a furnace with hot rocks on top. You throw water on the rocks to generate hot and humid air that fills the room, makes you sweat and purifies the soul.