Most homeowners know it’s important to move water that is discharged by their downspouts away from their foundations if they want to avoid seepage in the basement.
Some homeowners choose to install above-ground extensions from the big box store but many more have learned that underground downspout extensions do a better job of yard drainage. They carry water from your downspouts far enough away from your foundation to avoid creating seepage problems and do so without an ugly mess of plastic pipe snaking its way across your lawn. Installed properly, they have solved many a homeowners’ basement water problem.
Where some of those homeowners make a mistake is in asking their landscaping crew to install the downspout extensions. This usually doesn’t turn out so well.
Wrong Materials – A basement waterproofing professional will use solid PVC pipe in underground downspout extensions because it will be the most durable and will carry water to its end point. Landscapers typically use corrugated plastic pipe that is great for interior drain tile but not recommended for underground downspout extensions because it leaches water through its perforations.
Incorrect Pitch of Extension – Underground downspout extensions must be pitched properly to achieve proper drainage in your yard. Landscapers sometimes get this wrong, occasionally even installing them like an underground “U” that creates more problems than it solves by forcing discharge water to back up into the downspout. This prevents any flow at all and can do serious damage to the downspouts when the weather is cold enough to freeze (and expand) the trapped water.
Direct Connection to Downspouts – The best way to install an underground downspout extension is with a debris filter that will keep the pipe clean and can be easily maintained by the homeowner. Landscapers usually attach the extension directly to the downspout so there is no access to the system between the gutter and the discharge, which often results in clogs that have to be dug up to clear.
Extensions Too Short – To be effective, an underground downspout extension should carry water at least 10 feet from the foundation to get past the "zone of failure," the area that was backfilled when the house was built. Landscapers often install just a few feet of pipe in an effort to justify their low prices and, frankly, because they often don’t know any better.
I know that landscapers work hard and do a great job at the things they’re good at – they’re just not good at basement waterproofing. Rely on them to cut the grass and plant the shrubs; call a waterproofing professional to solve basement seepage problems.
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