What should be provided as a cover for the drain tile before installing the pond liner where a subdrain is used?

• A. 4 inches of pea gravel
• B. A pool grate
• C. Screen with a 1/4 inch mesh
• D. 8 inches of medium sized rock

Answer: (A)

Covering the drain tile with a layer of small, rounded gravel before the liner is laid protects the liner and keeps the drainage system functioning. A four-inch bed of pea gravel provides a forgiving cushion that won’t abrade the liner, allows water to reach the subdrain, and helps keep soil fines from entering the drain. This depth is deep enough to shield the liner and ensure proper flow, without creating a bulky layer that could interfere with seating the liner. Options like a pool grate are too rigid and can complicate installation; a fine screen tends to clog over time with sediment; and eight inches of larger rock is heavy, harder to place, and can impede proper drainage and liner fit.