What is the first step in troubleshooting a system that won't start?

The first step in troubleshooting a system that won't start is to check the power supply and controller settings. This is crucial because if the system lacks power or if the controller is not set correctly, the entire irrigation system will be unable to function. Ensuring that the power source is operational and that the settings reflect the desired schedule is fundamental to diagnosing any issues further down the line.

Once the power supply and controller settings are confirmed to be functioning properly, you can then move on to other potential issues such as checking for clogs in the sprinkler heads or inspecting the pipes for leaks. While these factors are important to address, they are secondary to ensuring that the fundamental elements of power supply and control are operational. If the system will not start, focusing on the power and control first is the most logical approach.