As shown in figure "A" and "B" of the illustration, the potable water pump is short cycling by the action of the pressure switch as a result of an unusually high level in the potable water hydro pneumatic header tank. What is most likely the cause? Illustration EL-0043

Correct Answer: Option D — The potable water hydro-pneumatic header tank is in need of recharging with compressed air due to absorption of air into the water over time.

Hydro-pneumatic tanks naturally lose compressed air over time as oxygen and nitrogen are absorbed into the water. Without a sufficient air cushion, pressure fluctuates rapidly under minimal pump delivery, causing short cycling as regulated by marine water system standards.