From the GMA Techline
Subject: HDPE and PVC — I am looking for reference material that indicates that HDPE liner and pipes, PVC pipes used in a landfill, are physically and chemically resistant to attack by solid waste and leachate. (Barbara, El Salvador)
Reply: You ask a very general question that depends on the characteristics of the waste and leachate. There are ASTM tests to address the situation, based on the specific materials and the specific leachate. They are immersion, according to ASTM D5322, and geomembrane testing, according to ASTM D5747. There is no direct test protocol for pipes.
That said, HDPE and PVC pipes and HDPE geomembranes are the most-resistant polymers to a wide range of leachates, and for this reason these materials are commonly used for landfill liner systems. Unless your leachate contains high levels of organic solvents, I think there is no great concern regarding chemical degradation.