If you notice a sudden drop in pressure in a force main, what is the likely cause?

• A. Air in line
• B. Broken force main
• C. Plugged force main
• D. Change in typography

Answer: (B)

A sudden drop in pressure in a force main almost always means a breach in the pipe. Force mains are pressurized by the pump, so when the line ruptures, wastewater escapes and the system can’t maintain pressure, causing a rapid decrease downstream. You may also see signs like wet ground, visible leakage, or unusual flow indicators near the break.

Air in the line can cause pressure fluctuations or pockets, but it doesn’t typically produce a sustained, system-wide pressure drop. A plugged main tends to cause high pressure upstream and restricted flow, not an immediate drop. The option about typography isn’t related to the hydraulic issue at all.