Downspout Extension Cost

• Simple aboveground downspout extensions going out 3-25 feet are about $10 -$50 each depending on length and type; the more expensive ones contract, roll up or swing out of the way, and some automatically extend themselves again when water gushes through them. Or for about the same cost, you can buy a length of downspout pipe that matches your existing downspout plus a gutter elbow to create your own extension. Having a handyman install this type of simple extension should take about an hour, and could cost $30 -$100, depending on local rates.
• The other option is to extend the downspout underground into plastic pipes that will either disperse the water aboveground at a distance from the home, into a small tank or drywell buried underground, or into an underground "energy dissipation basin," often called a French drain. Prices will vary considerably depending on the type and size of the system and the length of piping used. Although a simple underground downspout kit starts at $20, total do-it-yourself costs (including piping) can range from $100 -$400 or more. ThisOldHouse.com estimates that do-it-yourself installation of underground plastic drainage pipe for two downspouts on an average-size home could cost $100 -$300 and take 16-20 hours, depending on the length of the pipe and the hardness of the soil.
• Professional installation (typically by a landscaper) of underground drainage pipes can range from $200 -$2,000 or more depending on the amount of trenching and the size of the system. A New York homeowner paid $250 to have a landscaper extend a downspout through an underground pipe and into a small drywell located four feet from the house, while Galtech.com reports that professionally installed French drains cost $850 for 33 feet.

• Most premade downspout extensions come with simple instructions and are relatively easy to install. Just make sure it's firmly attached so a gush of storm water won't remove the extension. To create your own downspout extension to match your existing downspout, DoItYourself.com provides basic instructions for this relatively simple project.
• Underground drainage pipes are commonly 4 inches in diameter and installed about 10-12 inches deep, although this may vary depending on circumstances such as the slope of the land and soil conditions. SoundHome.com illustrates the design for a typical downspout-to-French drain system; Readers' Digest explains when it's a good idea to extend your downspout into an underground drywell.
• Call your local utility company before you dig, to make sure you won't be cutting into a power line. Also check with the local planning department before doing any extensive changes to downspouts; some communities have strict rules about where downspouts can drain (at least 5 feet from the house) or how they are connected to the public storm drain system. And make sure in advance that any drainage pipes won't cause flooding problems in a neighboring yard. Tip: Take pictures when installing underground pipes, so years from now you'll have a transferable visual record of where they are.

• Simple above-ground downspout extensions are available in most hardware and home improvement stores. Major manufacturers include Amerimax and Rainguard.
• Manufacturers of lightweight plastic drywells include NDS (Flo-Well) and Cultec.
• Typically, professional installation to extend a downspout underground would be done by a landscaper or a handyman with landscaping/drainage experience. Ask for referrals at your local nursery or home improvement center, or ask neighbors and friends for recommendations, or whether they've solved similar drainage problems.

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