Need Tips on Water Flow for Drainage Pipe

I think the standard for sewers is 1/4" slope per foot, and you have a bit more than that. I don't know if the corrugated pipe requires a larger slope. The worst-case gpm would also weigh into this.

I estimated the drop at six foot for 160 feet. That would be 72 inches, or almost half an inch per foot. I was worried about not getting it right, but every little bit is draining well.

Now I discover that the manhole cover size drain, near the end, just feeds into an old three inch drain pipe that appears to have been installed with the holes on top instead of on the bottom. It seems to be, predictably, 90% stopped up. The culvert is about six inches above my "flood plain" so I will just have to wait for the last six inches of water to soak in to lowest areas of the lot, or pump it into the culvert. This is something I can live with though.

I am waiting for a major rain event to test my progress. Your info gave me confidence as I loaded, hauled, and dispersed 128 bags of rock behind my riding mower.

Thanks

That's exactly what I'd recommend.

Line your trench (all the way around) with some type of geotextile to catch silt (such as "silt fencing" material that can be found at Home depot, Lowe's, etc just don't get the biodegradable type), put in some gravel bedding, pipe, cover with gravel. I would use a clean, washed gravel 3/4" to 1" size

The trench/gravel will convey a large quantity of water as well even without a pipe!

I am planning to have a gravel " creek" over the pipe. The water comes from all sides. The pipe is just for my neighbors pump and any really high unusual flooding. I have a drain on top of the pipe for that.

Does it make any difference if the pipe is not laid perfectly even, so long as the end is the lowest?

you're on the right path using a "creek" for primary surface drainage, so your shovel work will do double duty...

the drain fitting for the flex pipe generally have a silt trap

be careful about the depth if it's too shallow it can become crushed by trucks or other equipment

Thanks for the warning.

GA

Thats exactly what I did around my house 6 years ago, still works fine.

Hope this helps. jt. (nb. will not drain below natural water level.)

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It appears to me from nearly 35 years experience as a Civil Engineer (one of my specialties is drainage & hydraulics) that a 4-inch diameter drain pipe is way too small, as there is a tendency for said pipe sizes to severely clog-up with mud, soils of all types and vegetation. You're going to end up with a throughout clogged pipe that's going to require a whole bunch of labor-intensive maintenance.

We don't know the overall contributing drainage area (no just the lot size), and hence the peak stormwater runoff (+ groundwater contribution) flow rate that will impact the drainage pipe in question. If it is not too great an area, then I would suggest no using a drainage pipe less then 12-inches in diameter so as to avoid the clogging issue as much as possible and to efficiently convey the ponded water from the lot to the nearby stream.

You could use either corrugated HDPE (with smooth interior barrel) or PVC (SDR-35) pipe. I would install it at a 1.0% gradient (1 foot drop in every 100 foot horizontal run) as a minimum. If use install the HDPE type drainage pipe then make sure you wrap the joints with a good filter fabric as others have suggested above.

One more thing: bevel cut the entrance end of the drainage pipe at a 45-degree angle to help limit hydraulic entrance losses, to help limit scouring/erosion action; it should conform to the ground slope. Absolutely place cobblestones under and around the entrance and exit of the pipe. You should also installed cobblestone pads before the entrance (at least 4' wide x 8' long) and the exit (at least 6' wide x 12' long). I find that using cobblestones around 6-inches minimum (smallest axis dimension) work fairly well, are easy to install by hand, and not prone to be washed away or dislodged readily when there's a small through moderate stormwater runoff flowrate.

Make sure your pipe trench is deep enough to prevent the pipe from becoming buoyant due to groundwater influences....I suggest that the depth of burial be a minimum of 2 feet atop the pipe, but if you're located in the northern states that experience deep frost penetration in the ground then use a minimum of 4 feet of soil cover atop the pipeline.

Good luck!

You buy a house that some idiot built without adequate ground drainage, it's soon to hell with regulations.

The house built was on 2' of rubble fill footings in heavy clay.

I had to install drains on three sides of the house to stop flooding from three fields.

Drains were dug in to the clay 10' away from the footings.

I used 6" perforated pipe at a depth of 4'6" with ½" chatter as the base and above for about a foot. Above that and to within 6" of ground level, ¼ to 1½ crusher run.

It helped working in a quarry. The stone cost £0.20 a tonne. The digger a favour, the aggravation from the other half, eternity!

You've been given some fairly good advice here but I should add a few things. We get around a hundred inches of rain annually here where I live and I've been in civil construction all my life here so I do have a a fair working knowledge of what does and doesn't work for drain tiles. Smooth bore pipe is a necessity. The corrugated pipe traps silt. Dips in the pipe are a no no. Once again this traps silt. an 1//8 inch of fall to the foot will suffice if you carefully grade the pipe. Wye type clean outs placed a maximum of 75 feet apart will allow you to flush the pipe if necessary. Try to use 45 degree bends or less at angle angle points and install a clean out at the angle points. If you have much silt in your soils the filtration fabric around the pipe that people are suggesting will plug up. Screened rock around the pipe will divert most of it. A layer of non-woven filter fabric over the rock layer will work and would be easier to change out some day if necessary. And oh yes, 4" pipe will work if you follow all these guide lines but bigger is better if possible. The clean outs can be further apart if you up size but consider what you have available for flushing power. You may want to stick with the 75' guideline.

Good luck

PS I would use perf pipe and remember that the hole go on the bottom side, not the top as some would tell you.

Thanks for all the great advice. My house is built well above the flood level, but the sump pump is on about a third of the time. I have a five foot crawl space on average. I have a cement perimeter and no wood touches water.

The question is actually about an extra lot that I bought. It is sort of saucer shaped, and I am just trying to get it to drain as quickly as possible. My house and my neighbors drain in to this half acre lot. The builders were going to put another lot on it, but gave up the idea. The soil is heavy clay, with silt on top.

I am just going to make " dry creeks" going to the main drain and culvert for the lot. Sometimes half of it "ponds" for up to a week. we get about 45 inches of rain a year. One of the dry creeks will be over a non perforated pipe that drains my neighbors sump pump. Mine goes into a "dry creek" that I dug, and enjoy watching flow into the extra lot.

Sorry I wasn't explicit enough in asking my question.

Most of your question has been answered but in future if you have questions you can always refer to the Ten State Standards. It is more for Wastewater Treatment but this section on Sewer Design might be helpful for minimum slopes etc...

I would agree with earlier posts that it is important to use geotextile cloth to prevent clogging, install clean-outs, if you use perforated pipe make sure the perforations are facing down, and avoid sags in the pipe as it may lead to clogging or odor if organic materials enter the pipe.

Good luck.

You didn't mention what kind of orchard. Tree type will dictate whether you really want to drain it or collect the rainwater in the topsoil for the trees to use.

Seems like the 'lot' needs some more clean, topsoil fill material to fill in the 'saucer'.

Easiest way to get it is to put a sign out front that says: 'Clean free topsoil wanted.'

Dig your creek first so that the standing water goes where you want it to.

Then, when you plant your trees, mound around the root base with the soil from the hole you have to dig so that rainwater flows around their mounds to the 'creek' instead of standing around their root systems which might cause root rot.

If you use a harrow or disc to break up the top one foot of topsoil, more of the rainwater will soak into the water table.

It will also allow nitrogen to permeate into the soil which your trees will need. What trees you plant and how deep their roots grow will dictate how closely you disc to the base of the trees and how much ground water you will be wanting to keep on-site.