How are sprinkler valves typically kept in the open positions?

Sprinkler valves are typically kept in the open position by a locked chain. This method ensures that the valves remain open until manually closed for maintenance or other purposes. The locked chain serves as a physical barrier that prevents accidental closure, thereby ensuring the sprinkler system is ready to operate in case of a fire.

Using a locked chain is particularly important because it provides a secure way to maintain the system in an operational state, which is critical for fire safety. It ensures that personnel can check the status of the system visually, and the chain can often be inspected to confirm that the valve is indeed open.

In contrast, a manual lever could be used to open or close a valve, but it doesn't inherently provide a safeguard against accidental closure. A pressure gauge serves a different purpose, primarily to monitor the system's pressure rather than to keep a valve in an open position. Similarly, a temperature sensor is designed to detect conditions that might trigger the system but does not influence the valve's position directly. Hence, the use of a locked chain is the most effective method for maintaining the open status of sprinkler valves.