Which type of valve permits flow in only one direction and prevents backflow?

The check valve is specifically designed to allow flow in only one direction while preventing backflow. This function is crucial in systems such as fire service mains, where backflow could lead to contamination of the water supply or detrimental operational impacts. Check valves work by using a disc or flap that opens when fluid flows in the desired direction and closes when there is a reversal of flow or back pressure, effectively blocking reverse flow.

Other valve types do not have this specific feature:

• A gate valve is used to start or stop the flow of water but does not prevent backflow once opened.

• A ball valve can provide a tight seal and shut off flow when closed, but it is not inherently designed to prevent backflow in the way a check valve does.

• A butterfly valve is also used in regulating flow but lacks the backflow prevention mechanism seen in check valves.

Understanding the function of a check valve in a private fire service main system is crucial for ensuring the integrity and safety of the water supply being used for fire protection.