# Proper Drainage for Backyard and Patio?



## greentrees (Apr 28, 2012)

I had a concrete patio and walkway put in my backyard. 
The patio is sloped to the back fence, so rainwater will flow to the back fence and slightly to the left (if facing toward the back fence). When it rains, water flows from the back fence into the backyard. 

For drainage, I was thinking of digging a small trench and put in a plastic corrigated pipe and fill it with rocks. 

The small trench will ideally take any rainwater from the right half of the back fence and flow it to the right side of the house (when facing the back fence). I have another trench in the back of the patio, where the water from the left half of the fence will flow to the left side of the house. 

Under the tree, I packed in dirt/clay to build a higher area so the water flows to the right. Under the tree I will put plastic and cover it with rocks, so no water will absorb into the soil. The roots of the tree will hopefully grow toward the right side, where I will have a sitting area and ground cover/square blocks. 

Does this sounds like a good plan, or is there a better solution? I don't want water sitting around near the concrete and the trench seems like it should work. I just need to dig deep enough to have gravity move the water correctly.


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## Bondo (Dec 8, 2007)

Ayuh,..... You haven't posted any elevations,...

So,.... So long as it's *Downhill* in the directions of yer arrows,....

Ya, it oughta work...


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## concretemasonry (Oct 10, 2006)

If you want to drain with a near level line, do not use the corrugated flexible pipe because it does not drain well, accumulates silt and is hard to properly install of level or near level line. Use PVC and do it right.

Dick


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## greentrees (Apr 28, 2012)

Bondo said:


> Ayuh,..... You haven't posted any elevations,...
> 
> So,.... So long as it's *Downhill* in the directions of yer arrows,....
> 
> Ya, it oughta work...


The backyard is actually somewhat flat. But water comes from the fence into the backyard. So I will keep the dirt slightly tilted to the right and put rocks by the tree. The water should flow to the trench.

I need to dig some type of trench so the water flows to the right. I was thinking of starting the pipe just under the surface, with about 1 inch of rock on top. And than by the time I get to the drain, it will be about 6 inches deep (which means a 10 inch hole using a 4 inch pipe). I don't think I need much space on the side of the pipe, so maybe 1 inch of rock is ok? The pebble size?




concretemasonry said:


> If you want to drain with a near level line, do not use the corrugated flexible pipe because it does not drain well, accumulates silt and is hard to properly install of level or near level line. Use PVC and do it right.
> 
> Dick


I have some plastic corrugated pipe that has some holes in it to seap in moisture without seeping in dirt. Is there PVC that does the same thing? The attached photo shows a PVC with holes, but doesn't dirt just flow right in and clog it up?


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## AllanJ (Nov 24, 2007)

After the perforated pipes collect the water, where will the water go?


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## concretemasonry (Oct 10, 2006)

Some how, you have to minimize the movement of aggregate/soil fines without clogging into the perforated pipe that can be done with a cheap ineffecive "sock" or a rock/gravel backfill or with a filter fabric between the native soil and the backfill. Water always seeks its own level, even a level pipe with an outlet. Water in a perforated pipe entering through rock, gravel and top soil does not drain as fast as a concrete curb and gutter, no matter what you do. Buried drain tile have been used successfully for decades or centuries long before the big boxes found a way to combine two cheap materials (corrugated pipe and socks) for a quick solution with limited life and expectancy. There are thousands (millions) of acres of agrocultural land that has worked well for decades.

For many years, I played golf course with many hills and valleys and it was always playable. The subsurface drainage a 4 clay tile laid with loose joints was almost level, but with no dips. After the installation (40 years ago) it was graded so there was on opportunity to water to find a souce even dramatic short term storm or a long term rain because the drain tile led to an outfall at a lower elevation.

If you do not have an adequate outfall with capacity storage, you will have to pump it elsewhere (very rare) since that is where all rainfall eventually ends up, but can control the accumulation in the short term.

Dick


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## greentrees (Apr 28, 2012)

AllanJ said:


> After the perforated pipes collect the water, where will the water go?


The water should drain to the right side of the backyard (when facing the fence). There is a drain pipe that flows from the backyard to the front of the house. I tested it with a hose, and the water went through ok. 

I can probably move the dirt around and tilt the land so water flows right to the drain pipe, but it will carry with it a lot of runoff clay, which will probably clog up the pipe. 

If I guide the water with a perforated pipe surrounded by rocks, the clay will build up slowly around the rocks. If I put a filter in, the clay will build up at the filter. Either way, hopefully it is many years before I have to clean it again.


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