We have found those "drippers" to be frustrating too. We bought some when we had only a few chams - and ended up returning them to the store. Then we went to margarine cups with a small pinhole in the bottom edge. These proved reliable to drip, as long as you kept them cleaned out weekly (mineral buildup at the pinhole). Now that we have hundreds of chams, hubby designed a timed drip system that works off of a R/O unit and a 55 gal tank.
I have suggested a IV drip unit for folks with a single cham. If you poke the base into a bucket (seal with silicone), then place the dial (for speed of drip) and dripper over the proper place, it will drip continuously until it empties the bucket. The catch is gravity - the water has to flow down! The bucket needs to be higher than the dripper and tubing.
Nursing homes and clinics, etc., must toss out IV units all the time when they have gone past the expiration date on the unit. Yes, they have a shelf-life, for medical reasons. We get our IV units free from these sources. You can shorten the tubing, if necessary, with a bit of ingenuity.
If you have no one to check in on your cham while you are gone - have you considered taking the cham with you? We know several folks that have done this - but of course, they were traveling by car.
The only other thing we can suggest, is to place the cage in your shower. Turn on the shower (barely dripping) over one corner of the cage so that the water falls on some leaves. Depending on your cage - you can sit it up off the floor of the shower for water drainage. Even though we prefer not to use tap water - it is certainly far better than having no water for the animal.
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