What is required between a check valve and the boiler in regards to feed valves?

In hydronic systems, a manual shutoff valve is required between a check valve and the boiler to control the flow of the water or fluid in the system. This configuration ensures that maintenance or service can be performed safely without draining the entire system or disrupting the operation of other components.

The manual shutoff valve provides the ability to isolate the boiler from the rest of the system, allowing technicians to work on the boiler or check valve without affecting system pressure or flow elsewhere. This isolation is critical for safety reasons, as it helps prevent accidents during maintenance tasks where water or steam could be released unexpectedly.

In contrast, while a pressure gauge is useful for monitoring system performance, it does not provide isolation. Similarly, a drain connection and a vent valve serve different functions related to maintaining fluid levels and removing air, rather than isolating components for maintenance. Therefore, the manual shutoff valve serves a unique and essential purpose in the operational integrity and safety of the hydronic systems.