Replies

1. 
   Guest_ | Apr 02, 1999 12:45am | #1

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   RWD2

   Run the downspout to a dry well. Keep it well away from the house (check local codes) The size and depth will depend on avg. rainfall and conditions.

1. 
   Guest_ | Apr 02, 1999 02:19am | #2

   *Being a clay soil, water that goes into your drywell will take a LONG TIME to percolate out of the drywell. So, you need to size it carefully. To size your drywell, assuming you'll be using gravel, estimate the volume of stormwater that would run off your roof in a certain time period for the worst storm event (pick your poison - 1-hr, 2-hr, 12-hr, 24-hr, 48-hr period; worst storm event based on a 25-yr, 50-yr, or 100-yr recurrence). Your local big-city library or university library will have precipitation maps with this data.Divide this volume by the porosity of gravel (depends on what type of gravel you use - best for you to actually measure it in a 5-gallon bucket). For example, say the precipitation map gives a value of 12" of water (based on the time periods you chose), and your roof occupies 1000 square feet (horizontally). That's 1000 cubic feet of water. Let's say the gravel you're using has a porosity of 35%. 1000/0.35 = 2857 cubic feet of gravel needed. This is about 100 cubic yards, or 5 truck loads. The precipitation value is probably (hopefully) too big for real-life, but this is just an example.If you consider the volume of water capable of being stored in the pipes, then you can reduce the size of the drywell accordingly. If you use sand for the drywell instead of gravel, you complicate the situation because you need to consider the rate at which water will flow through the sand based on its hydraulic conductivity, porosity, and the water pressure applied. Water will flow rapidly through gravel, until it gets clogged with all the junk coming out of your gutters! For that reason, you may want removable filters at the bottom of each downspout.

1. 
   Guest_ | Apr 02, 1999 03:27am | #3

   *Chris, Time on your hands or what?The guy wants a bunch of ideas, not the formula for the installation of a nuclear substation.The local building people would have been able to tell him the size required, even the excavation contractors, would know that required size, once they would have had a look at the soil conditions.KISS

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   Guest_ | Apr 02, 1999 06:21am | #4

   *... and maybe he'd like enough property left over for a tree or something.It's unclear to me that he needs the dry well -- is there nowhere downhill to send the water? And if the underground pipe (no longer a "downspout" right) is solely for removing roof runoff, use solid pipe. I used the inexpensive smooth 4" PVC drain pipe to escort excess water off the property. If you want a french drain setup it gets more complex, but the project is really about sweat equity. (Be smarter than me and get someone to drop by with a Bobcat!)A neighbor's back yard is -below- street level and floods with water every storm; it probably receives runoff from adjoining properties. There is no practical way to regrade because of the small lot size and building & pavement placement. I haven't looked hard, but cracks in his brick walls suggest to me that the foundation is on the move from all the water.I suggested a drywell/patio, but this would only contain some of the water. Should he consider pumping the excess water out, sump style, as a cost-effective solution for now?

1. 
   Guest_ | Apr 02, 1999 03:23pm | #5

   *Why do they call them "French" drains ?Because the water keeps going down on you ?(sorry - I just couldn't resist...............)

2. 
   Guest_ | Apr 02, 1999 04:32pm | #6

   *RWD2,assuming you live in civilization,instead of some wasteland,keep it simple.pvc to the street. Let the cities storm sewer dispose of the water.Of course if you have a new house the city may not allow this method for new construction. An existing home is prob. grandfathered in to allow this system and it works great.

3. 
   Guest_ | Apr 03, 1999 01:28am | #7

   *Dear R2D2:Uhh..so when its underground, what were your intentions? To the street? To a dry well? I once was called in on a drainage issue, where the homeowner did a great job funneling all the water from downspouts into a french drain, that led nowhere. It just filled up with water, and flooded his basement.Assuming you want to take it to a dry well, the other post provides more than enough infomation. Use 4" solid PVC.Assuming you want to have the pipe gather more water from the soil (to protect your basement), consider a french drain. Use 4" perforated ABS, and look up some posts on how to do that.Incidently, are you in the Star Wars remake this go-around?

4. 
   Guest_ | Apr 03, 1999 02:03am | #8

   *RWD2You can use either 4" PVC or 4" flexible black plastic drain tile. The PVC is a more permanent solution. PVC is less likely to clog, and is less likely to crush in case something heavy like a car is driven over them. Assuming you have at lease some slope away from your house, (not a perfectly flat lot) and unless you have a backhoe to dig the drywell these guys are talking about, simply exit the pipes to daylight, or in other words, leave the ends of the pipe uncovered. Be careful where you exit the pipes though, as they can cause some wash-out.I use one downspout drain that also receives the condensate from our AC unit in my yard to water a raised hydrangea bed. Hydrangea is a water loving plant.

2. 
   figuers | Apr 03, 1999 04:13am | #9

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   they are called French drains after Henry F. French who wrote a wildly popular book in 1859 called farm drainage. Little has changed in sub-drain design between 1859 and now.

   some points to ponder. It is unwise to use perforated pipe within 5 to 10 feet of your house foundation. All you do is put water beneath the foundation (the worse possible place). To size the perforated section, treat it as a septic drain field. (it is the same concept - you are getting rid of liquids). Do not use flexiable pipe. Use rigid PVC with the holes down (this is what henry showed - must mind our elders). also remember to install cleanouts every 100 feet or so.

3. 
   Guest_ | Apr 03, 1999 08:34am | #10

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   figures:

   That's interesting about Henry F. French.

   Do you think that when installing foundation draintile the pipe should go beside or on top of the strip footing?

4. 
   Rob_Dykeman | Apr 03, 1999 06:01pm | #11

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   Check out article at the Permenant Building and Foundation web site about basement drainage.
   http://www.pbf.org

5. 
   RWD2 | Apr 03, 1999 06:01pm | #12

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   I am getting ready to landscape my new house and want to run the gutters underground instead of using downspout extensions. I live in the Mid-West with clay soil. What is the best way to do this. PVC? Perforated 4" drain pipe?