How should manual shut-off valves be installed to ensure accessibility?

For the proper installation of manual shut-off valves, ensuring they are readily accessible is crucial for safety and efficient operation. Valves should be positioned in a manner that allows quick access in emergencies or maintenance situations. This means they should be located where they can be easily reached by anyone who may need to operate them, particularly during urgent circumstances.

The idea of them being concealed is not suitable if it compromises access. Concealing a shut-off valve could lead to difficulties in locating and operating it when necessary, which can have serious implications during emergencies. Therefore, the emphasis on accessibility ensures that anyone can quickly turn the valve on or off if needed.

The other options do not meet the necessary criteria for effectively ensuring safety and accessibility, as they either suggest unwanted concealment or restrict access to professionals only, which is not in line with best practices for installation and safety management.