had a pondless waterfall installed last fall. I love it, except that
it does have a leak and I suspect a large one. Loose several inches of
water a day and will empty out completely in course of about a week.

It has been my experience that leaks (or water loss) are usually the result of
excess waterfall splashing outside the contained area, overflow from the liners
edges and/or capillary action or seapage at liner overlap joints. I'd check
those areas again before replacing the liner itself. I hope this helps. Good
luck.
-Pat Rolland