Question 427General Subjects - Assistant Engineer

The correct answer is A) The hydro-pneumatic expansion tank is operating with an insufficient air charge. A hydro-pneumatic expansion tank is used to maintain consistent water pressure in a plumbing system by compressing air above the water level. If the air charge is insufficient, the tank will not be able to properly absorb pressure fluctuations, causing the pump to short cycle (rapidly turn on and off) to try to maintain the desired pressure. This is the most likely cause of the issue described in the illustration. The other options are incorrect because a low water level in the potable water storage tank (C) or in the hydro-pneumatic tank (B) would not directly cause pump short cycling, and excessive clearance in the pump wearing rings (D) would not be the primary cause of the problem.