GFS Leachate Tanks: Why Landfill Leachate Defeats Most Coatings Landfill leachate is not one liquid, and that is the core of the problem. It is a variable, concentrated mixture whose composition shifts with the age of the landfill, the weather and the waste stream that produced it. A coating chosen against a single analysis of a young leachate can be badly wrong five years later, and by then the tank is full, the site is operating, and replacing the vessel is an emergency