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How Do Gutter Covers Work?

For hundreds of years rain gutters have been used in house design. Many different materials have been used over the centuries starting with stone, later zinc and wood, and today aluminum, galvanized steel, or copper. And as long as there have been rain gutters, there has been the need to regularly clean out the gutters because they have always collected and filled up with leaves, twigs, seeds, and other debris.

What is needed is something that will allow the water to pass through but will catch and hold any solid material being carried along by the water. Various inventive people have created all kinds of solutions. Today these are marketed as gutter guards, gutter covers, gutter screens, or gutter filters.

The simplest solution is some kind of gutter screen. There are a number of different kinds currently available. Many of them employ a sheet of what is called expanded metal, which is made from a flat sheet with diamond-shaped holes. When water is poured on the screen it readily runs through the holes. A similar plate can be made from vinyl or plastic material by casting the holes.

Anything larger than the holes is caught and held back. The holes are rather large, and small pieces (broken pieces of leaves, dirt, etc.) can pass through. In addition, pine needles or leaf stems that hit the holes point-on can enter the holes. They may pass through or get stuck in the holes. Screens can become clogged with caught material and require periodic cleaning.

Sometimes very fine dust or dirt is blown or sucked up into the air by winds or storms. This material can be picked up by raindrops and carried down with the rain. This fine material will readily pass through the diamond-shaped holes.

An alternative approach is to use a plate with long, narrow slits to pass the water. The width of the slit in such a gutter guard is much smaller than the dimensions of the diamond-shaped hole screen. This will prevent much smaller solid matter from being carried into the rain gutter. The flow rate through these slots will be somewhat slower than through the expanded metal screen. Most of the solid material stopped by the slot plate will be washed off the plate by the rain. Some may accumulate on top of the plate. This will normally dry out after the rain stops and be blown off by the wind.

Another strategy is to use a gutter cover. Water has a characteristic called water tension that makes it act like an elastic sheet. This is what allows water spiders to flit around on the surface of a pond. Capillary action makes the water try to stick to the surface of the gutter cover.

Visualize a gutter cover with a horizontal flat-top surface and a half-circle curve on the left end. If a BB slowly rolled across the flat plate to the curve, it would then follow the curve from the 12 o’clock position until it got to the 9 o’clock position. Gravity would then make it fall directly to the ground.

If water were flowing over that same cover, the water would follow the curve from the 12 o’clock position all the way to the 6 o’clock position. If a short vertical tab were located at that point the water would run down the tab. Gravity would then make it fall. On a rain gutter cover, the lip of the cover is positioned so the debris falls outside the rain gutter, but the water falling from the tab falls inside the gutter.

With every one of these systems the idea works, but not perfectly so. There is always a little bit of debris that gets carried into the gutter by the moving water—but not much. However, a gutter filter may be the best solution yet. Instead of a filter or a cover, this system uses a piece of open cell foam that completely fills the top of the gutter. There are no open holes, no gaps, and only the tiniest bits of material, smaller than the very small foam cell size, can try to enter. The debris does stay on top, does dry out, and is blown away by the wind.

Installing one of the different kinds of gutter protection systems can avoid a lot of trouble, hassle, and home maintenance, whether you choose gutter guards, gutter covers, gutter screens or gutter filters. They all function to keep debris out of the gutter and keep water flowing freely through the gutter. The designs differ considerably, and the need for periodic maintenance is not entirely eliminated—you may still have to clean out the gutter, but only rarely rather than two to four times a year.