What maintenance action is critical for ensuring the proper function of surge tanks?

Maintaining adequate air space in surge tanks is essential for their proper function. Surge tanks are designed to absorb sudden changes in water pressure within a distribution system. The air space allows for the expansion and contraction of water, effectively mitigating pressure surges that can occur due to rapid changes in flow, such as valve operations or pump starts and stops.

When the air space is adequate, it provides the necessary cushion that prevents water hammer and protects the integrity of the piping system and other equipment from the stress of pressure fluctuations. If the air space is too low, the tank may not function properly, leading to potential system instability, equipment damage, or even failures in the water distribution system.

While the other choices like chemical testing, rust inspection, and flushing are important aspects of general water tank maintenance, they do not specifically address the function of surge tanks in pressure management. Maintaining the correct air space directly supports the operational efficiency and safety of the water distribution network.