Ok here is the quick version. Large pond install last year, consistent water loss complaints. Pond has a two tier waterfall approx 15 ft high. Customer turns pond off frequently to save electricity, thus allowing waterfalls to drain down. We have turned off plumbing and monitored water level for 3 days, no loss. We have makred level and let pond run for 3 days, no water loss. Customer says he sometimes losses a couple inches in a night. Any ideas other than a thirsty bear???