We often get asked if downspout strainers will work to help keep leaves and other debris out of the downspout. The answer in most cases is yes they do work. There are many different types of downspout strainers, this model happens to be a plastic material. Gutters still need to be cleaned out at least once a year. While the strainer may help to keep debris from clogging the downspout it can also keep water from properly draining all the way out of the gutter. This creates a slime in the springtime that can coat the strainer and cause clogging issues.
Strainers for the most part do a good job of straining large debris from getting caught in the downspout tube, or even worse in the underground pipes. But they are not a substitute for regular maintenance. Gutters are meant to channel water, not hold a bunch of debris. Over time this will cause damage to the home. If you have strainers installed think of them as extra protection for the downspouts, not as a solution to keep the gutters from overflowing.