Serious UV rot (degradation) is most common in cheap, unreinforced materials that lose their flexibility when exposed to the sun. To prevent this, professional-grade manufacturers use carbon black, a powerful additive that acts as a permanent, molecular-level sunscreen for the liner.
BTL's RPE liners maintain a 3.0% concentration of carbon black, matching the industry standard for high-performance, UV-stabilized geomembranes. To get a liner rated to last 20+ years at the waterline, you need to look beyond the retail stores and buy from a source that provides this level of verified chemical protection.
