When beginning an aluminum rain gutter replacement project, you can avoid wasting time and money if you know in advance the potential mistakes that are most commonly made. Then, do what you can to avoid making these same mistakes.
Aluminum rain gutters installed with a slope that is too shallow, will often overflow when a high volume of water drains from the roof of the home. You can't always predict the volume of water that will flow through one of these gutters, but you can avoid creating a slope that is too shallow to move an average volume of water. The best slope will be 1 inch for every 20 feet of gutter length
For aluminum gutters that are 40 feet long—or more—avoid draining all roof water through one downspout located at the end of the gutter. You will get more efficient drainage if you begin your gutter pitch at the middle of the gutter, and slope it to drain to 2 downspouts, 1 at each end of the gutter.
Gutter Attachment Location
Avoid attaching your aluminum gutters to your roof edge. Instead, attach them to the rafter tails, that will more likely bear a greater weight without breaking.