What type of valve acts as a one-way check valve?

A backflow valve functions as a one-way check valve, designed to prevent the reverse flow of fluids in a piping system. This is critically important in plumbing and fire protection systems to ensure that contaminated water does not flow back into the clean water supply. When fluid is flowing in the intended direction, the valve remains open, allowing for normal passage. However, if there is a reversal in flow due to pressure changes or back siphonage, the valve closes, thereby protecting the system from potential contamination. This mechanism is key in maintaining the integrity and safety of water supply systems.

In contrast, a butterfly valve is primarily used for regulating flow rather than functioning solely as a check valve, while a gate valve is utilized for on/off service and does not prevent backflow on its own. A pressure relief valve is designed to release excess pressure but does not restrict reverse flow like a backflow valve does. Thus, the backflow valve is uniquely suited for the specific function of ensuring unidirectional flow within a system.