What would 2 pipes coming from a piece of building equipment be?

• A. Expansion Tank
• B. Storage Tank
• C. Drain Line
• D. Vent Stack

Answer: (B)

Two pipes coming from a piece of building equipment usually signal a storage function—the device holds a quantity of liquid and needs a way to fill it and a way to deliver it. A storage tank is designed to store water or other fluid and must have an inlet and an outlet, which is why you’d see two pipes exiting it. Other options serve different roles: an expansion tank helps absorb pressure changes in a line, and while it can be connected with more than one pipe, its job is not to store but to protect the system; a drain line carries wastewater away and is generally a single discharge path; a vent stack is part of the drainage vent system and runs vertically, not providing a feed from the equipment. Therefore, two pipes from the equipment best indicate a storage tank.