I filled up the base with water first. I used plain old tap water. Once I found there were no leaks whatsoever, I rinsed the old girl out with RO water. I have a Zero TDS unit under my sink because I need distilled water for my marine tank, and needed it to make beads. I get a lot of use out of it, so it made it very worthwhile.
Someone will ask, "Won't the water ruin the humidor?" or "Shouldn't you use distilled water for everything?" The best I can answer is no and no. It's just cheap wood.
Water won't hurt any wood, so long as it's preconditioned. In the shop I use a spray bottle with distilled water to wet my wood, that way it won't stain. Then I can use all the regular water I want and it won't leave a mark.
A guy just has to think a bit, ya know?
If you use dirty water when the wood is dry, the wood will suck in the dirt. Use clean water first, then the wood can't suck dirt cause it's already wet.
Not a single drop leaked from the base, despite some large seams and lots of patching.
I only half filled the unit once the top was on. I didn't want the weight of the water to cause me to break the glass. With the humi 1/4 full, I turned it up on all sides to check for leaks. Nothing. It's 100% leak-free.
All emptied out and ready to get dried.
Sitting in front of the barrel fan to dry so it doesn't warp. I should mention here that the water should only be in the humi for a very short time. Otherwise it will warp.
I should also mention that I taped off the holes in the hygrometer, and I had sealed it with silicone a long time ago. I also sealed the handles, they were really bad.
The light in this last pic looks really blue. It's from the lights in the kid's lizard tank. I'm too lazy to fix the pic.
And the last of it all...