Sounds like you are watering the poor tree to death. There is no way your Japanese maple needs that much water unless it is planted in pure sand. I live in the South where we have extended spells with temperatures above 90 and dry weather, and I seldom water my J. maples -- perhaps once a week during very dry weather. Wetting the leaves should be fine when you water as long as it's morning or early afternoon and the tree has a chance to dry before night.

Based on your description, it's a bit hard to say exactly what the problem is. Generally, daily watering of an established Japanese maple is unnecessary, but there's watering and then there's watering. Overhead sprinkling everyday may not be supplying enough water to the root zone and the tree is simply displaying the signs of drought stress. Or conversely, you ARE overdoing it and both too much water as well as constant wetting of the foliage is causing problems. Too much water as well as insufficient water will provide very similar symptoms. Unless as a remedy to wilt of newly planted trees, hosing down the foliage is not recommended and Japanese maples often tend to have very delicate foliage which can be damaged by water on the foliage in hot and sunny conditions.

In general, a deep soaking at the root zone weekly should be sufficient in all but the hottest and driest weather. If the plants surrounding the maple require more frequent watering, address them individually or move to a better location. Tickling the plants with water daily is just a waste of water and often results in wasted plants as well :-)

Thanks you both.
The plants around it are in various containers including bonsai pots.
I'll have to move them or the tree.
If that doesn't work it may be a fungus or wilt.
If there are other reasons for what's happening I'll appreciate advise on how to handle it.
Paul