What should be placed over a drain tile prior to installing a pond liner?

• A. 2 inches of sand
• B. Metal grate
• C. 4 inches of gravel
• D. Clean soil

Answer: (C)

When installing a pond liner, you want a protective, well-draining layer over the drain tile so the liner isn’t punctured and water can reach the tile effectively. Four inches of gravel provides a sturdy cushion that shields the liner from sharp edges or rocks, distributes weight evenly, and maintains an open, permeable path for water to flow into the drain tile.

Two inches of sand isn’t ideal because sand can shift, settle, and migrate, which can clog drainage paths and compromise the liner protection. A metal grate isn’t necessary here and can interfere with proper liner placement or create points of pressure on the liner. Clean soil would compact and fail to protect or facilitate drainage, making the system less stable.

So, the best choice is four inches of gravel.