Water levels in a pressure tank rise due to which of the following factors?

• A. Air leaks in the tank
• B. Absorption of air by the water
• C. Both A and B
• D. Temperature changes

Answer: (C)

The main idea is that a pressure tank’s water height is controlled by the air cushion at the top and how much air is in that cushion. The air in that space acts like a spring that balances the water pressure. If air leaks into the tank, more air gets trapped in the cushion, changing the balance and allowing more water to fill the tank during cycling, which shows up as a rise in the water level. At the same time, some of the air can dissolve into the water under pressure; as that air leaves the cushion, the space for air shrinks and water occupies more of the tank, raising the water level. Because either increasing the air in the cushion or removing air from it shifts the air–water balance, both processes can cause the water level to rise. Regular checks of seals to stop leaks and maintaining the proper air charge help keep the level stable.