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I have about a half acre mildly sloped with soggy grass. The previous owners had dug a drainage channel but it has failed or is not catching the water correctly. This is causing water to collect around the surrounding area. Is a channel drain the kind of thing to take care of this, like the premade trench drains at Home depot or is burying a french drain the appropriate measure here? The final outbound pipe is slightly lower graded than the flooding spots, but not significantly.

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Drainage can be tricky. Some of the factors that should guide your decision are:

  • does the soil drain well? Loam or sand drain easily. Clay does not.
  • do you get temperatures that are cold enough to freeze the ground which can lead to issues in the spring when the snow melts and the ground does not absorb water
  • is the direction you want the water to go in a straight line from the house?
  • is the area that is down hill where the water will drain on someone else's property? You don't want to export your problem.
  • is this project a "good enough job" or do you want to be able to sleep at night even if you have a foot of rain in a day?

The materials to address a drainage issue are available at most hardware or Home Depot style stores. One of these is 4" black drain pipe with sleeve. It is available in 100' roles or custom lengths and fittings are available to add a T or Y junction.

  • flexible, can curve around corners
  • relatively inexpensive
  • after it is buried can be crushed over time by overhead foot traffic or heavy soils
  • unless you are careful black drain pipe will follow any dips in the trench leading to low spots where all the water will drain out
  • corrugations in the pipe can allow soil to collect gradually making it less effective

White pvc pipe with holes is another alternative

  • more expensive
  • more durable, does not crush easily
  • works better when installed in straight lines
  • can be flushed if it silts up
  • water flows faster down the smooth pipe wall

These are my recommendations for your situation and it is based on the idea that you only want to do this once so do it right.

  • the existing ditch seems to lend itself to a straight line of pvc pipe that is predrilled with holes. (Sometimes called irrigation pipe)
  • dig a ditch from 6 to 8" inches deep. Ensure it has an even slope towards where you want the water to go. Use a laser level if you have one.
  • line the ditch with landscape fabric
  • lay the pipe, no need to glue it, friction fit will do the job
  • wrap the pipe with the landscape fabric
  • connect your downspouts to the pipe with a fitting, (possibly a 37.5 degree angle Y fitting?)
  • at the highest point add a 45 degree fitting and an end cap so you can flush out the pipe later. You can set the cap at ground level or cover it with a stone
  • at the lowest point which should be at least 20' feet away from your house dig a hole and make a dry well. Reuse a plastic container like the ones used for bulk paint or drywall compound and cut the bottom out. Put this plastic sleeve in the hole and fill with large rocks. Direct the pipe into the well. Cover with landscape fabric
  • do a test with a hose. From the highest point where you added your fitting run water in and verify that it eventually fills the dry well
  • back fill the trench with soil and sod or seed

Note that in hot, dry weather the grass above the pipe will brown out so the deeper you can bury the pipe the better

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A channel drain at the low side will primarily get surface water, which means the lawn draining into it needs to be fully saturated and running water on the surface before it's effective. If water is flowing across the surface onto the lawn, a channel drain at the high side might be helpful to intercept that flow.

If you want the lawn to be less soggy, a french drain system under it would indeed be the typical approach. That system will need somewhere to drain that is lower than its pipes.

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