Tom, here’s one from Jim in Champions. He says…
“Every house I have lived in had roof gutters that had no pitch toward the downspout. Why is that?” He says, “With the replacement gutters it’s always required to have a pitch.”
Very slight pitch. Actually just 1%, so that could be 1 inch and 10 feet at the most. You don’t even need that. Water will find the opening and will flow down. They do require a little bit of pitch, but even if you had most 0 pitch it would still almost drain but it would drain enough when it’s raining to where it wouldn’t back up. There might be a little bit of water after the rain in the bottom which will evaporate so if you don’t want a pitch you could actually get away with it, but you don’t want a negative pitch in the wrong direction.