What action should be taken after setting the bypass valve to the service position?

After setting the bypass valve to the service position, starting the system is the appropriate action. This step is critical because the system must be activated to assess the effectiveness of the service performed and to ensure that water is flowing correctly through the system components after maintenance or repairs. Starting the system allows for the detection of any potential issues that may arise during operation.

It's essential to follow the correct sequence of actions when servicing water treatment systems. Opening another faucet does not verify the function of the system itself, and checking for leaks is typically done after the system has been started to confirm that the connections hold under pressure. Connecting the power supply is also a necessary step, but it precedes starting the system and does not assess the system's operational status. Thus, beginning the system operation is the required next step after altering the bypass valve position.