A good rule of thumb for a gutter slope is that you want at least a quarter inch of slope for every 10 feet of gutters.

What is the pitch for rain gutter?

To ensure that gutters drain properly, make certain they slope (½ inch for every 10 feet) toward a downspout. For gutter runs longer than 40 feet, it’s best to pitch the gutter down from the middle to a downspout at each end.

How much slope should a downspout drain?

We want our drain pipe to have a 1% slope so water will always drain properly. That means the trench and drainpipe must slope away from the house with at least 1-inch (2.5 cm) of fall for every 8-feet (2.4 m) of run.