Cooling Water Storage Tanks: Closed-Loop vs Open-Loop and Treatment Data center cooling water lives in two worlds: a closed chilled loop that must stay clean, and an open condenser or cooling-tower loop exposed to air, evaporation, and treatment chemicals. The storage tank design and lining differ between them, and so does the failure mode. This article covers the tank through the lens of loop type and water treatment. A cooling water storage tank for a data center must match