What is a rainwater diverter and where can I buy them? 

A rainwater diverter helps disperse heavier flows of rainwater over a wider space of your gutter to lessen the chance of the water running over your gutter. A typical location of where you would install a rainwater diverter would be on your inside miter gutter (roof valley intersection). It does this by keeping most of the organic debris from piling up on top of the stainless-steel mesh.