Water Under Pond Liner: Causes and Solutions for a Floating Liner

Why Water Gets Under the Liner

Groundwater pressure (hydrostatic pressure) pushes up on the liner when the surrounding soil is saturated. This is common in spring after heavy rain, especially if the pond is in a low spot or near a high water table. It can also come from a leak in the waterfall, stream, or plumbing that tracks under the liner.

Diagnose the Source

• Turn off the pump for 24 hours. If the liner settles, the leak is in your circulation system.
• Check the waterfall/stream: Look for wet spots along the edges, especially at seams.
• Inspect the liner edge: Is the capillary barrier (liner folded up behind edging stone) intact? Water can wick over the edge.

Solutions

1. Install a drain pipe under the liner: A perforated pipe in gravel, leading to a lower discharge point or sump pump, relieves groundwater pressure. Best done during installation, but can be retrofitted at one edge.
2. Build a berm: Redirect surface runoff away from the pond perimeter.
3. Weight the liner: Add more rock/gravel on the shelf areas (not the bottom drain area) to hold it down.
4. Fix any plumbing leaks.

If the pond is in a natural low point with a high water table, a drain system is the only permanent fix. Consult a pond builder for site-specific design.