Pond Liner Floating? High Water Table Solutions

After heavy rain, your new pond liner bulges upward, pump runs dry. No holes found. The culprit: groundwater pressure.

Why It Happens

• Saturated soil raises the water table above the pond bottom.
• Water exerts upward buoyant force on the liner (Archimedes’ principle).
• Liner acts like a balloon—floats on trapped groundwater.

Fixes (Least to Most Invasive)

1. Perimeter Berm: Build a 6–12 inch soil berm around the pond edge, especially on the patio side. Directs surface runoff away and adds weight.
2. French Drain: Trench 12–18 inches deep around pond, line with fabric, fill with gravel + perforated pipe to daylight or dry well. Lowers local water table.
3. Under-Liner Drain: If rebuilding, lay perforated pipe in gravel *under* the liner, connected to a sump pump or gravity outlet.
4. Raise the Pond: Convert to above-ground using retaining blocks or timber. Eliminates buoyancy issue entirely.

Immediate Triage

• Weight the liner temporarily with sandbags or smooth rocks.
• Run pump to lower internal water level *slowly*—rapid drawdown increases pressure differential.
• Do not cut the liner to "let water out"—creates a permanent leak path.

The patio slope toward the pond likely channels runoff underneath. Concrete collar (as sketched) on that side seals the edge and diverts water.