Kim Farlow
Depending upon the diet and environmental temperature and the work load put on your horse his water consumption could be normal but not likely. The extra water has to be going somewhere. If the 'wet spot' in his stall has not increased and he is not sweating more then something is wrong. He my have a case of psychogenic water consumption. You will need to get your vet involved in this and see if the two of you can bring this puzzle together. I would also suggest they check his kidney function.
Thanks, Dr. Lowder