What type of valve is used when two storage tanks serving the same area have different overflow elevations?

An altitude valve is specifically designed to manage the water levels in tanks with varying elevations, ensuring that overflow does not occur at inappropriate times. In the context of two storage tanks serving the same area with different overflow elevations, the altitude valve plays a crucial role in regulating the flow between these tanks based on the water levels. When the water level in the higher tank rises to a predetermined level, the altitude valve will close, preventing any further inflow, while allowing the lower tank to fill to its own designated level. This helps maintain efficient operation and prevents possible overflow from the tanks.

The other options represent different functions and are not suitable for this scenario. A relief valve is used to relieve excess pressure, a pneumatic valve operates based on air pressure for controlling flow, and a pressure relief valve is focused on dropping pressure in a system. Thus, the altitude valve is the most appropriate choice for managing the overflow from tanks with different elevations.