A standpipe is considered ground storage unless it exceeds ___ feet above the highest service connection.

• A. 60 ft
• B. 80 ft
• C. 100 ft
• D. 120 ft

Answer: (B)

The concept being tested is how water pressure from a standpipe is provided by gravity and how height affects whether it can be treated as ground storage. Water stored in a standpipe that is at or below a certain height above the highest service connection can rely mainly on gravity to deliver pressure to the outlets, so it’s considered ground storage. When the height exceeds that threshold, gravity alone won’t maintain adequate pressure at the topmost connections, so pumping or other pressure-boosting measures are needed and it’s no longer treated as ground storage.

That threshold is eighty feet above the highest service connection. Beyond this height, the static head from gravity is not sufficient to meet firefighting pressures, necessitating alternative means to maintain the required pressure.