Experiment a bit. If you tilt the water chamber the right direction at about 45 degrees, it breaks the "air lock" and you can pour fast. Be sure not to overfill, or water may pour back out the air inlet and damage the blower unit once you put it back into the machine.
If you try to overfill it, then sit it on a level surface, water will pour out, but don't rely on that to set the water level. If it's that full, let it drain, then pour out a little more.
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If it's midnight and a DME tells you it's dark outside, go and check it yourself.
I also had this same problem. I didn't realize there was an "air lock" that stopped the water from directly going into the tank. I've watered my nightstand many evenings. I started separating the tank to fill it. I thought it was a pain at first but now it doesn't bother me. It's just part of the routine.