A pump connected to a hydro pneumatic storage tank that cycles on and off is a result of:

• A. Not enough air in tank
• B. Too much air in the tank
• C. A high pressure limit that is too high
• D. A low pressure limit that is too low

Answer: (A)

The pump cycling on and off is usually caused by not enough air in the tank. The stored air acts as a cushion that absorbs the water volume as the system pressure changes. When there isn’t enough air, there’s little room for the water to be stored under pressure, so pressure in the tank drops to the lower cut‑in quickly, the pump starts, the tank fills, pressure climbs to the upper cut‑out, and then the cycle repeats rapidly. In short, the air cushion is too small, so the system can’t sustain a steady pressure and keeps turning the pump on and off.

To fix it, restore the proper air charge in the tank to the manufacturer’s recommendation and check for leaks or a failing bladder—these issues can lead to a loss of air and the same cycling symptom. The other options don’t explain the rapid on/off behavior as directly: they alter switch timing but don’t address the essential cushion that prevents short cycling.