How to add a downspout in an existing gutter step 1.
Install gutter downpipe.
Drill a hole in the bottom of the gutter at the 4 inch mark with a 1 inch hole saw attachment to the drill.
Watch and learn how and stop.
Gutters over flows add downspout to bring water down from roof faster.
Its easy less than 30 minutes and under 30 00 in parts.
Fit the gutter in place which normally just clips in with the appropriate stop ends connectors and gutter outlet for the downpipe.
You can double check the fall with your spirit level.