Water loss may come from evaporation, splash-out, an overflowing edge, plumbing, or a damaged liner. A water-level record is more useful than guessing from a single low reading.
Start with observations, not sealant
Mark the normal operating level at a fixed point and record it at the same time each day. Note rain, wind, top-ups, and pump operation. If an automatic refill is hiding the loss, have a professional explain how to monitor it safely without leaving the pump or fish short of water.
Check where moving water goes
From a safe position, look along the waterfall and stream for water diverted outside the lined area. Plant growth, debris, and a low edge can change the path. Wet ground is a clue, but irrigation and rainfall can also explain it.
When testing needs professional help
A controlled comparison with a waterfall on and off can narrow the search. For a stocked pond, arrange suitable independent aeration and a safe plan first. Do not leave a pump off for a fixed period simply because a generic checklist says to do so.
What the pattern can tell you
Loss associated with pump operation points attention toward the circulating system; loss while the system is safely isolated warrants attention to the basin and its fittings. Neither pattern proves the exact fault. Groundwater beneath a liner can also complicate diagnosis.
Prepare for an assessment
Share the water-level record, whole-pond photographs, recent landscaping changes, and photos of wet areas. Ask the professional how they will isolate the source, which material they intend to repair, and how the repair will be verified.
Explore pond leak repair or check referral availability. This guide is general homeowner education, not an on-site diagnosis or emergency service.
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