Plugged Underground Drainage

Why is the patio under water?


We have a walkout basement that opens to a below-grade concrete patio. Although there are four drains in the patio area, it's covered with water every time it rains. Can we clear these drains or will we have to dig up the yard to install a new drainage system?
— Richard Fosgate, Waterford, MI


Roger Cook replies: You have clogged drainpipes or a clogged drywell, or both. But your yard — most of it, anyway — should be safe. To fix the problem, call a company that specializes in drainpipe cleaning and have them do what they can. They'll have to work carefully, though, because drainpipe is easy to break. Many of these companies have camera scopes — cameras at the end of long cables — that can be snaked down drains to pinpoint obstructions. If the scope shows that the pipes are clear, then you have a clogged drywell, which will have to be dug up and removed.
To locate the drywell, ask the drain cleaners to snake the drainpipes until the snake won't go any farther. If they have an underground pipe or metal detector, they should then be able to pinpoint the location of the drywell. Otherwise, you'll have to measure out the snake's length aboveground, in the general direction indicated by the pipe, and hope that you hit it as you dig.
Now comes the hard work: Dig up the old drywell and replace it with one made of concrete block, precast concrete, or lightweight plastic. But before you bury it, take some measurements from at least two permanent landmarks, draw a sketch of the drain system and its dimensions, and put it in a safe place. Someday you may need it.
To help keep your pipes clear in the future, replace the existing patio drains with PVC or metal bell drains, which have a clean-out reservoir to catch some of the debris before it gets into the drain system.


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