Green Plumbing

Answer: B - The terms “open and closed” have been redefined as “direct and indirect.” In solar water heating systems, “open” and “direct” mean that the system has potable water circulating directly through collectors prior to delivery to the hot water fixture. “Closed” and “indirect” mean that the system employs a heat exchanger to heat the potable water prior to delivery to the hot water fixture, through the use of a collector medium.