A dropping pond water level does not always mean the liner is leaking. Water loss may be caused by evaporation, splashing, low liner edges, plumbing leaks, or damage to the pond liner.
The best way to determine whether your pond liner is leaking is to turn off the waterfall pump and monitor the pond's water level for 24 hours.
Step 1: Check for other causes of water loss
Before assuming the pond liner is damaged, inspect the following:
- Evaporation: Some water loss is normal, especially during hot, dry, or windy weather.
- Low liner edges: Settled soil may allow water to escape over the edge of the pond liner.
- Waterfall or stream: Splashing, displaced rocks, or excessive plant growth may redirect water outside the liner.
- Plumbing connections: Leaking pipes, fittings, or pump connections may cause water loss while the pump operates.
Step 2: Perform a 24-hour water level test
- Fill the pond to its normal operating water level.
- Turn off and unplug the waterfall pump.
- Mark the water level on a rock or other stationary surface.
- Leave the waterfall pump off for 24 hours and monitor the water level.
- Compare the water level with the original mark.
Important: If fish are present, maintain adequate aeration and oxygen levels during the test.
Step 3: Evaluate the results
If the water level continues dropping with the pump off:
- The leak is likely within the pond itself.
- Allow the water level to continue dropping while monitoring the pond.
- When the water level stabilizes, inspect the liner around that elevation for punctures, tears, or other damage.
- Also inspect the skimmer faceplate or other penetrations near that water level.
If the water level remains stable with the pump off:
- The pond liner is less likely to be the source of the leak.
- Inspect the waterfall, stream, plumbing, and filtration connections.
- Look for water escaping over low edges or splashing outside the liner when the pump operates.
Step 4: Inspect the pond liner
If the water level test indicates a possible liner leak:
- Identify the approximate area where the water level stopped dropping.
- Carefully move rocks or gravel covering the suspected section of liner.
- Inspect the exposed liner for holes, punctures, tears, or damaged seams.
- Check nearby areas for wet soil or other signs of escaping water.
Important: Avoid using sharp tools when moving rocks or inspecting the liner. If the pond contains fish, do not allow the water level to drop to an unsafe depth.
Once the damaged area is identified, an appropriate EPDM liner repair patch may be used to repair compatible EPDM pond liner.
For additional information, see Aquascape's guide to identifying and fixing pond leaks.