Pond Leak Diagnosis: Liner vs. Waterfall vs. Splash Loss

Water dropping overnight with no visible liner leak means the water is going somewhere — and there are only three real possibilities.

The Three Leak Categories

1. Main liner leak: Water drops even with pump off. Check: wet spots outside liner, soft soil, muskrat holes, root punctures.
2. Waterfall/stream leak: Water drops only when pump runs. Check: shifted rocks, liner flap under rock, splashing outside liner, cracked plumbing.
3. Splash/evaporation loss: Excessive waterfall splash, wind drift, or hot/dry weather evaporation (can be 1–2"/day in summer).

Definitive Test Protocol

1. Turn off pump completely. Mark water level. Wait 24 hrs.
2. If level drops: Main liner leak. Proceed to liner inspection.
3. If level holds: Turn pump on. Mark level. Wait 24 hrs.
4. If drops now: Waterfall/stream/plumbing leak.
5. If holds with pump on: It was evaporation/splash — or intermittent leak.

Liner Leak Fixes

• Small puncture: EPDM patch kit (clean, prime, patch, roller).
• Large tear/age: New liner. Use geotextile underlayment.
• Water under liner: Install drain pipe (perforated, daylighted) under liner at low point — suck/siphon to remove.

Waterfall Leak Fixes

• Re-stack rocks with liner flaps over next rock down (shingle principle).
• Use waterfall foam (black expanding) to seal gaps and direct flow.
• Check pump hose connections — barbed fittings + clamps.

Water doesn't vanish. The 24-hr pump-off test tells you exactly where to look. Stop guessing — start testing.