Dualline™ Double Wall Tank’s strong, durable, quality construction is designed for the containment of all chemicals rated for contact with polyethylene. Dualline™ tanks are freestanding double wall vertical tanks with a flat bottom for indoor or outdoor stationary applications. Double wall construction provides containment in the event the inner or primary tank is compromised. AN EPDM elastic seal is standard and seals the primary tank to the secondary tank to prevent dirt and moisture from entering the containment space between tanks.