What Causes Gutters to Clog?

Why is the sky blue? Why do birds fly in formation? Why do leaves turn from green to brown in the fall? Why do fools fall in love?


“WHY do they fall in luh-huvvv?”

It’s not practical to solve all of these mysteries here. But since this is a blog about gutter protection, it is an appropriate forum to answer a commonly-asked-yet-still-vexing question: why do gutters clog?

Here’s the short answer: because they are flawed.

Gutters Have Drainage Problems

The first major issue with modern gutter systems is one that has plagued structures for centuries: the fact that a large drain runs into a smaller drain. Because that’s all gutters really are: “drains” that are mounted to your home.

Consider this: a 30-foot section of standard 5-inch gutters holds about 36 gallons of water at one time. All of that water is supposedly flowing toward a single two-by-three inch downspout opening (sometimes two), then past one or two downspout elbows before exiting the gutter system. In even a moderate rainstorm, the large quantity of flowing water is likely to back up to some degree, giving time for solid debris to deposit itself somewhere along the gutter or downspout.


“Don’t hate me because of my flaws. Nobody’s perfect!”

Gutters Have Sloping Problems

And then there’s the issue of slope. Depending on who you talk to, gutters are generally hung with a slope of anywhere between one quarter and one half inch per ten linear feet. This allows runoff water to flow “downhill” to the downspout openings.

But here’s the problem: the ideal slope should be a quarter inch for every single foot of guttering. That’s the slope used by plumbers who run waste lines, because this slope allows the water to flow fast enough to carry solid debris along with it. Since gutters are almost never set this steeply, the water flow is insufficiently rapid to transport leaves, twigs, pine needles, and other debris through and out of the downspouts. Therefore, this debris tends to remain in gutters and form clogs.

What’s the Perfect Gutter?

This begs the question: is it possible to construct a gutter system which eliminates these flaws. Probably. But let’s imagine what it would look like.

First, the gutters would likely have to be quite wide — perhaps seven, eight, or even twelve inches across the troughs. So they would stick out father from the roof line and necessitate stronger support hangers in order for them to remain level and prevent water spillover. Also, the gutters’ incline would be much more drastic. That 30-foot section of gutter would have one end positioned a full 7 1/2 inches below the other. Finally, there would probably be multiple downspouts positioned in order to divert rainwater more quickly so that clogs don’t form.

The result might be functional, but it may be cumbersome, unsightly, and possibly non-compliant with local building codes.


In other words, it might look something like this. Only uglier.

So What Should You Do?

The bottom line is that homeowners will probably have to accept the inherent flaws in their guttering systems. This may necessitate cleaning out their gutters two or three times per year (or hiring someone else to do it) in order to prevent clogging and the myriad problems which can result from improperly-deposited water. Of course, investing in a gutter protection system to keep solid debris out of the gutter in the first place might also be a smart choice.

The moral of the story? The sky is blue, birds will fly in formation, leaves will change colors, and gutters are likely to clog. But given the foundation problems that can result from having no runoff drainage at all, gutter systems are definitely the lesser of two evils.