Pond Liner and Underlayment

Pond Liners – EPDM, RPE, and Box-Welded Options

A quality pond liner is the foundation of every water garden and koi pond. Play It Koi carries pond liners in all major materials — EPDM rubber, RPE (reinforced polyethylene), and custom box-welded liners — plus underlayment, seam tape, and liner repair supplies. Whether building a small backyard water garden or a large-scale koi facility, the right liner ensures decades of leak-free performance.

EPDM vs. RPE Pond Liners

EPDM (ethylene propylene diene monomer) is the most popular pond liner material. It's flexible, UV-resistant, fish-safe, and conforms easily to irregular shapes. Standard thickness is 45 mil for most residential ponds. RPE liners are lighter, puncture-resistant, and available in thinner gauges that perform comparably to thicker EPDM. RPE is an excellent choice for large ponds where weight and shipping cost matter.

Box-Welded Pond Liners

For formal rectangular or square ponds, box-welded liners provide a clean, wrinkle-free installation. These liners are factory-welded to your exact dimensions and drop directly into the excavation. They're especially popular for above-ground koi ponds, quarantine tanks, and Japanese-style garden ponds.

Liner Sizing and Underlayment

Calculate liner size using: Length + (2 × Depth) + 2 feet overlap × Width + (2 × Depth) + 2 feet overlap. Always install geotextile underlayment beneath your liner to protect against rocks, roots, and ground movement. Pro tip: in rocky soil, use a double layer of underlayment or a sand bed for extra protection.

Liner Care and Repair

EPDM liners last 20+ years with proper installation. Small punctures are easily repaired with EPDM patch kits and seam primer. For pond construction, pair your liner with proper edging materials to create a professional finish. Quality plumbing fittings with bulkhead adapters create watertight pipe penetrations through the liner.

Pond liner and some underlayment ship at their own rates, shown at checkout, and aren't covered by free shipping over $99. Contact our team for custom liner sizing assistance.

Related Categories

Construction Supplies · Pond Kits · Plumbing & Fittings · Pond Pumps · Pond Filtration