Hmm. Here is a You Tube review of K-Guard. Not good.
Yep, I saw that... and others. In fact, I found YouTube videos like that for every gutter guard system I found. This guy doesn't say what kind of guard he was installing, but the videos show some kind of screen. It's easy to find videos, (and to just imagine), pine needles and stuff stuck in those screens. They will require regular cleaning.
I was getting real frustrated looking for a solution on the web. There are horror stories and videos about every system. Then talked to my fishing buddy. A recommendation from a friend in my area seems more trustworthy than a web video.
When the guy came out for an estimate, I asked him about debris coming thru the gap. He said some can, but the key is to install the gutters with a proper slope. If the gutters are level, the debris will sit, and eventually collect. With a proper slope, the small amount of debris will wash to and down the downspout. It makes sense. And the gutters can handle 12"/hour of rain. It's more than I expect.
Whatever you decide, I would look for a local, family owned business to handle installation. The one I chose has been here 30 years and uses their own installers, not contractors.
So to me, the keys are proper installation and reliable service if there's a problem. The lifetime warranty is as much about the local franchise owner as the product.
If you can find a gutter guard product that doesn't have horror stories on the web, please let me know... if it's before Tuesday.
