Taco flow-through expansion tanks are designed to help reduce the environmental conditions that help bacteria flourish in domestic hot water systems. Precise flow channeling technology controls the flow within the tank, minimizing erosion potential and promoting turbulence. The full-acceptance Captive Air design provides separation of air and water for optimal efficiency. All models are designed and constructed per ASME Section VIII, Div. 1, and are NSF/ ANSI 61-G certified.