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Do sub-surface drains (e.g. French drains, rubble drains, etc.) require a uniform rise in the water table in order to work? Or can they catch and convey localized sub-surface water?

For instance, let's say my neighbor allows water from their garden hose to accumulate in one spot on their lawn near our property line. As a result, the soil there becomes soggy and water logged. Can I install a sub-surface drain on my side of the property line to prevent this water from transmitting through the earth towards my home's foundation?

Moreover, if my sub-surface drain does catch that ground water, what prevents the water from falling back out of the pipe as it flows downwards towards its ultimate destination? What causes the water to stay in the pipe even though the pipe is full of holes?

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A French drain doesn't move the water anywhere it just creates a void that can be filled with water for the short term. You could do the same thing by burying a barrel with holes in it and landscape fabric around it. Eventually it would get full of water and if the rain (or garden watering) doesn't stop it will still flood the area.

Nothing prevents the water from falling back out of the pipe except hydraulic pressure. But that is the idea. As the ground dries back out the water leeches back into the soil. There is not usually an ultimate destination but you could create one by connecting solid pipe to the perforated pipe running downhill to another area.

You can certainly do this on your side of the property to help reduce flooding.

  • Some drain into a dry well, ir into a sump which is then pumped elsewhere – keshlam Nov 20 '15 at 16:52
  • So hydraulic pressure keeps water from falling out of the drain (which is what I expected.) However in the example I gave, there's only hydraulic pressure in the area around the garden hose. So as they French drain conveys the flow away from the boggy area, the water will fall out as soon as it reaches dry soil. This may be well short of our final destination (e.g. dry well, open trench, storm sewer etc.) Is there any way around this? – AlfaZulu Nov 20 '15 at 17:48
  • Yes connect solid pipe to the perforated pipe until you get the water where you want it. And then convert back to perforated pipe in a gravel bed or dump it into a low lying area. Of course, if the water leeches out on the way it will do so into dry soil so it should accomplish your goal even with perforated pipe the whole way. – ArchonOSX Nov 20 '15 at 20:35

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