A hot water boiler will have gravity circulation within the system unless a _________ is installed

A hot water boiler will have gravity circulation within the system unless a _________ is installed

• A. Pump
• B. Vent
• C. Flow check
• D. Circulator

Answer: (C)

Gravity circulation happens when hot water rises and cold water sinks, creating a natural loop in the system when the boiler isn’t actively circulating. Installing a flow check valve in the line from the boiler provides a one-way flow path: it lets water leave the boiler when the pump is running, but blocks reverse flow due to gravity when the system would circulate on its own. This prevents unintended gravity circulation. A pump or circulator would actually cause circulation, not prevent it, and a vent just releases air without stopping the flow.

Gravity circulation happens when hot water rises and cold water sinks, creating a natural loop in the system when the boiler isn’t actively circulating. Installing a flow check valve in the line from the boiler provides a one-way flow path: it lets water leave the boiler when the pump is running, but blocks reverse flow due to gravity when the system would circulate on its own. This prevents unintended gravity circulation. A pump or circulator would actually cause circulation, not prevent it, and a vent just releases air without stopping the flow.