In the case of the Care-Free type of gutter cover clogged louvers can be cleaned with a telescopic pole and brush from the ground, but the bigger problem is the excessive amount of decaying debris that gets into the cistern.
A superior design to the Care-Free gutter cover is the best double row louvered gutter guard as you'll find it in two types of gutter protectors-google the "Waterloov Leaf Guard" and the "Number One Gutter Protector" to see the difference between a single row louvered gutter guard and the best gutter covers with two rows of louvers.
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Whereas the Niagara single fin type of leaf guard keeps out approximately 92% of the debris, the single row louvered CareFree Gutter Guard keeps out approximately 96% and the double row louvered Waterloov and Number One Gutter protectors keep out over 99.5% of the debris.
With regard to the louvers of the water collectors clogging, they can easily be seen from the ground and brushed (cleaned) with a telescopic pole and brush assembly.
In summary, it makes sense to install the double row louvered–the best gutter guard–system that will keep the most debris out of your gutter and still be easy to maintain from the ground.