I'm still kind of a newby, but if it helps, here's what I did. I drilled a hole in mine (carefully, away from all the wiring) and inserted a piece of 1/2" pvc at an angle. I put a 45 degree angle on the bottom aimed down into my reservoir and a threaded male fitting and cap on the top (outside the bator). Now I can unscrew the cap, add warm water with a funnel, then put the cap back on. The great thing is it gives me an extra ventilation source for that critical "lockdown" period. After loosing some chicks in my first hatch that had internally pipped but didn't hatch, I did some research and found that people sometimes make the mistake of DECREASING ventilation to increase humidity, and this can actually suffocate the chicks since not only do they use the air pocket, but the shells are also porous and allow air to pass through. Reduce the air flow and you force the chicks to use up the air stored in the bubble without any way to replenish it. Next hatch, I had the pipe in place and swapped out my reservoir for one half again as large right at lockdown. Humidity stayed up even with the pvc cap off, and all my pips successfully hatched. Since then, I've had two more hatches (different bator but same design) and I currently have 30 eggs on day 5 of another hatch.
Edited by spiritdance - 1/20/11 at 10:03pm