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French Drains vs Channel Drains?

Posted by advertaddy GA (My Page) on
Fri, Feb 26, 10 at 18:18

I have a drainage issue in my backyard where there is a slight swale in the middle that collects rainwater. I've had a few landscapers give me estimates and options regarding how to fix this. 1 person said to install french drain pipe + solid pipe leading out to the street for the water to drain out. Another person says to install 2 channel drains+solid pipe leading out towards the street for the rain to drain out. In your opinion what would be the better option? This is a difference of approximately $400-500 in pricing between both jobs. Im more concerned with what will work than money. I'll be honest, I've never seen channel drains in a yard before. However, i've seen them in driveways and near stairwells. Also, how does one maintain channel drains? Wont it get cluttered with debris? Thanks!


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RE: French Drains vs Channel Drains?

  • Posted by laag z6CapeCod (My Page) on
    Fri, Feb 26, 10 at 19:45

There are lots of ways to approach it, but channel drains would not be a typical approach. The first concern is sediment, but aestheitics and how it may conflict with how you use the area would be others.
The advantage is quick intake of water, but there are other ways of doing that as well such as an open gravel trench with perforated pipe disguised as a "dry creek bed" (which then could connect to solid pipe).
The term "french drain is often applied differently by different people, but is generally understood to be a subsurface leeching trench with some sort of grate that allows the water in.
Drainage tile would be subsurface perforated pipe taking in water and carrying it elsewhere. These only work in saturated soil conditons.


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RE: French Drains vs Channel Drains?

Thanks for your reply. The quote for the french drain is the following. Let me know what you think:
Installation of 32' French drain, 90' of 4'' corrugated drainpipe to capture stormwater in backyard & from 2 right side downspouts & deposit water in street to run down drain. Work to be completed by hand with minimal disruption to turf & includes tunneling underneath sidewalk, cutting and repouring concrete curb @ street


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RE: French Drains vs Channel Drains?

Call local landscapers and ask if they are building a patio or walkway in the area. The excavate quite a bit of dirt in doing walkways and they have to get rid of it somewhere. Have them dump it right in the depression and you can spread it around with shovel and rake (or hire someone to grade it--smooth it out). Then seed and straw it. Blend the new soil into the surrounding grade. This will solve your problem and make your yard look best all around! Let me know if you want me to go into that further.


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RE: French Drains vs Channel Drains?

  • Posted by laag z6CapeCod (My Page) on
    Sat, Feb 27, 10 at 8:00

Filling a depression only works if the end result is an effective downhill path for the water to follow.

Advert, How do they describe what the surface treatment is of that 32' "french drain"? If it is gravel open to the surface, it would be an effective way to collect the water.

I'd rater see pvc used because if it is pitched, it will keep the water moving at a speed that would move any sediment that gets into the pipe along with the water. Corrugated is a lot more likely to vary in pitch allowing water to slow down and deposit sediment in the pipe. Corrugation slows it down on its own as well. The problem gets worse if the bottom of the trench is not graded to a consistent pitch. Many landscape crews either don't understand that, don't believe that it matters, or are more worried about getting the job done so the pipe tends to have its ups and downs. Then it eventually clogs.

PVC has two rows of holes with a smooth bottom valley in between for the water to run. As the trench fills the water rises and enters the holes and drops into the valley. Then it justs shoots down that pitched valley at a contant speed, if it is a constant pitch.


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RE: French Drains vs Channel Drains?

brandon & laag,
thanks for your replies. I dont know if this helps more, but here is a photo of after a regular rain session.
http://i60.photobucket.com/albums/h16/oldeschool17/House/DSCN1312.jpg
When it really downpours the drainage issue is much more spread out.
I believe the landscaper said that gravel would be used, but I will check.


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RE: French Drains vs Channel Drains?

  • Posted by laag z6CapeCod (My Page) on
    Sun, Feb 28, 10 at 7:21

I would not have a problem with a channel drain along the slab.


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RE: French Drains vs Channel Drains?

As a general rule, it is not economically feasible to size subsurface drains to handle the water when the big rain comes. Thus subsurface drains can lull one in to thinking that surface grading if acceptable and results in unanticipated flooding.

In my opinion, you have asked many questions and got good and true answers. But it is likely that you have asked the wrong questions and the answers are worthless.

Drainage is very site specific and you have given us little of the important particulars needed for the design of a solution to the problem. Perhaps your question should have been "How do I go about finding a fix for this drainage problem".


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RE: French Drains vs Channel Drains?

Fair enough. I was always under the impression that a french drain and re-grading were the typical fixes to this solution. If I might ask, what other details or variables are needed to better determine what solution I should go about?


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RE: French Drains vs Channel Drains?

Under some conditions french drains provide a means to de-water saturated soil. Where the soil is not saturated it makes little sense to create that condition and then solve the problem with a french drain.

Water in the landscape is beneficial to plants in the right amounts. It can be damaging to both plants and structures in the wrong place. Rainfall has an economical value as it minimizes the cost of supplemented water. And it has legal issues as well.

In dealing with all the issues of water, it's easy to fix a problem in one place only to create one in another place. The cost of regrading and drainage remediation makes it smart to get it right the first time. Tunnel vision leads to unanticipated problems. It's best to consider all aspects across the entire property, not just the problem area. A comprehensive plan for the entire property leads to the best cost / benefit ratio.

A good place to start is by completing a detailed base map of your property. Close attention should be payed to where water enters and leaves your lot.

The water entering your lot represents a potential for flooding if grading does not discharge the water from a maximum storm event.

Under the currant condition, after the water fills the depression shown in your photo, the excess runs off and exits your lot somewhere. If you change this exit location you will be liable for any damages caused and you might be made to undo the changes.

The elevation that water leaves your lot is a resource. The lower the elevation, the greater the possible solutions you will have for drainage features.

Considering this, do you have confidence in the contractors and their proposals? Did they provide you will a detailed plan that you have not shared with us? Will either one work? Myself, I don't have a clue.

You can hire someone to do a base plan ($300-400?) or you can do it yourself with some instruction. Or you could just cross your fingers and hope for the best.


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RE: French Drains vs Channel Drains?

To be honest, I cant think of any other variables to mention that I have not allready done to better analyze how to go about this project. However, Im welcoming all feedback as I lack the expertise in this matter and want to make sure I do the right thing. With regards to the confidence in the work, i would say Im somewhat confident, however, this would be the first time i've ever hired this individual, much less have something of this magnitude done for my home. When it rains, the middle of this yard is saturated with rainwater and takes awhile to dry up/runoff. I feel that regrading the backyard ONLY(not install the french drain) will not be the solution because it would appear that there would be a chance that water will flow towards the house versus out. However, im not qualified to make that assessment By installing this french drain and regrading appropriately, it should help with the problem. Should I post more pics of the yard to get a better perspective of what I am working with?


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RE: French Drains vs Channel Drains?

  • Posted by laag z6CapeCod (My Page) on
    Mon, Mar 1, 10 at 7:11

A trench drain on the edge of the patio would take the water off of that patio once the swale fills to where it is coming onto the patio. The patio itself is not big enough to need to worry much about the runoff created by it.

If the puddling on the patio is the main issue, the channel drain will take that water away once the swale fills to that point. Then you could just let the swale infiltrate over time.

If you want to get rid of all of the excess water from the swale, you could skip the channel drain at the patio and dig out the bottom of the swale. Grade the bottom of the trench for an even slope. Line the trench with silt fabric. Add an inch of 3/8"-1/2" gravel to bottom to keep the pipe just off of the fabric. Then put perforated pvc pipe with the two rows of holes toward the bottom and fill the trench with washed 3/4" gravel. You could dress the top with larger river rock. You need to keep the stone open to the surface in order for this to work properly. Of course the piping needs to continue to its end destination at a constant or increasing slope in order to keep sediment from setting in the pipe.

The question is whether you want to have stone on the surface.

The best thing would be to grade the property for possitive surface drainage, but it is assumed that you can't do that for some reason.


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RE: French Drains vs Channel Drains?

advertaddy,

I hope I have not offended you with my curt replies. Others have said this is sometimes not a friendly forum to visit. I may be a part of that. I assure you it has nothing to do with you. Most of the regulars here seek to be helpful but we often fall short of achieving that result for a host of reasons. It can be frustrating.

I hope you dont mind that I post a small copy of your photo so that I can refer to it.

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Comparing the photo with my 50 years of experience with terrain and construction, several things are suggested. I have drawn a level blue line along the back of the house that matches the lines of the siding. This is the level plane from where the photo was taken. Assuming the photo was taken by a person standing, the line across the door indicates the house floor is only slightly higher than the backyard grade. I would expect a house on a concrete slab with a 2 to 8 inch drop from floor to patio level.

Most slab construction is built on lots having 3% or less natural slopes. Thus the street grade is likely 1 to 2.5 feet below floor elevation. For your sake I hope it is closer to the 2.5 difference.

There appears to be a small cut in the natural grade to the rear of the house to accommodate the slab construction. On the right of the photo we see the resulting upslope that probably is less steep past the cut area. The size of the upslope area is unknown but represents the possibility of a significant quantity of water that may flow to the flat behind the house.

The fence looks to be 6 ft tall and the level plane intersects it close to the top indicating the grade there is slightly below that where the photo was taken. There does not appear to be any swale turning the corner to take the water to the street. Could it be that the only exit for water is under the fence?

With the present grading and the fence acting to limit high flows, I would not be surprised to see a water depth of one foot back there in a major storm event. Now how much was that floor above the back yard?


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RE: French Drains vs Channel Drains?

  • Posted by laag z6CapeCod (My Page) on
    Mon, Mar 1, 10 at 13:06

... and I thought the swale was coming toward me, go figure.


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RE: French Drains vs Channel Drains?

...and you might well be right. Nothing is certain photos. That's why we still use tapes and levels.


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RE: French Drains vs Channel Drains?

Thanks guys for your input so far. I find this very helpful and welcome the honest feedback. Id rather you guys be blunt as its what I need. Forgive me if I seem rather naive or am not able to fully answer your questions. With regards to stone, id rather not go that route if possible due to aesthetic and practical purposes, unless I am misunderstanding. I have a dog that plays in the back so I want her to have as much space to romp without getting hurt or have an excuse to mess up all the work that would be done. Re-grading for positive flow is definitely an option I would like to consider, but I just worry that if I only do that and not install the pipe/drain, that it will have a higher chance of running towards the house. Is that a fair concern(based on those pics/scenario)or am I overreacting? A

I've posted up additional images to get another perspective of my backyard. To answer the question regarding where it drains, I'm almost positive that the water drains towards the left by the door(under the fence). You can tell due to the thatch near there and the wear of the grass as well. In addition, it seems like the yard has the most positive flow going in that direction. Certainly, the left side of the house leading down to the street reinforces that theory as you can see how the water runs off down in that direction. In terms of distance, the street is much closer towards the right but there isn't a positive flow going towards that way and it doesn't naturally drain in that direction. With regards to the right side of the blue line, its not that much steep, as its just a few trees and mulch. With regards to a heavy rainstorm, the water has ebbed very close towards the storm door but has never flooded into the house thankfully. With regards to a heavy rainstorm and how high the water can get near the patio, i've never measured the depth of that so I can't give a solid answer unfortunately. I think in the worst case situations, if I were to step out there with a pair of regular sneakers that were non-waterproof, id have some very wet shoes. It's very soggy in those areas when it rains whereas the rest of the backyard is not nearly as soggy. It certainly takes longer in these areas to dry up/run off in comparison to the other areas of the backyard.
http://i60.photobucket.com/albums/h16/oldeschool17/House/diagram.jpg
http://i60.photobucket.com/albums/h16/oldeschool17/House/DSCN1360.jpg
http://i60.photobucket.com/albums/h16/oldeschool17/House/DSCN1361.jpg
http://i60.photobucket.com/albums/h16/oldeschool17/House/DSCN1362.jpg

Thanks again guys for your help and patience.


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RE: French Drains vs Channel Drains?

Just got done talking to the landscaper and the gravel is not open to surface. We have Bermuda, so that would get cut and reinstalled after the drain is installed.


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RE: French Drains vs Channel Drains?

  • Posted by laag z6CapeCod (My Page) on
    Mon, Mar 1, 10 at 21:47

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RE: French Drains vs Channel Drains?

Good. Now we have some effective communication going. The sketch is a very crude base map and will need improvement, but we can do that later. For now we can see the scope of the proposal and start to assess its effect.

I would like to take some time now to explain what is really happening in your backyard. Hopefully, in a way that is understandable.

Picture a 5 gal bucket with a inch hole drilled in the bottom. On the side very near the bottom is another inch hole. Above that hole are two inch holes. Going up the side of the bucket are an ever increasing number of holes and the hole size also increases.

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Put the bucket under a faucet and dribble some water in. The water all runs out the bottom hole. Open the faucet some more and water will build up and start to run out one or more of the side holes. Open the faucet more and the water depth increases. Now note, for any given flow rate the water depth stabilizes when the outflow equals the inflow.

Think of your backyard as a very shallow bucket. Rain on the upslope runs in and the water depth increases until the outflow rate equals the inflow. To change the depth, one must either limit the rate of inflow or maximize the rate of outflow.

Now lets look at how different amounts of rainfall effect the rate of inflow. Suppose with relatively dry soil there is a half inch rain. All of the water is absorbed by the soil and none runs down to your backyard.

With a 1 inch rain, half an inch is absorbed and the other half inch runs to your backyard. The flow will have very little depth; probably less than an eighth of an inch and will travel very slowly down the slope. While the rain may come in an hour, the water reaching your yard may be spread over a much longer time.

Up the rainfall to 2 inches and now you a get 1.5 inch runoff, three times what a 1 inch was. And the depth of water running down the slope is increased. This increased depth produces a dramatic increase in the speed the water travels. The combination of water quantity multiplied by the increased speed can result in a flow rate many times what a smaller rainfall produced.

Consider now the storm that occurs only once in 20 to a 100 years; perhaps a 5, 8, or 10 inch rain over a 3 hour period. It would not be unusual to get a flow rate that is 20 to 50 times greater than with a common 1 inch rain. For a situation where a 4 inch drain pipe is adequate for a normal rain, it is woefully undersized for larger storms, where its capacity is likely to be less than 5% of what is needed.

What I am trying to point out is the importance of assessing the amount of drainage area that contributes water to your backyard and how it affects the problem you have.

The proposal for the french drain with a cover of topsoil would only have a very delayed increased in outflow and thus would have little to no affect on the maximum water depth in the problem area.


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RE: French Drains vs Channel Drains?

I know that is just a sketch but I think the French drain should be extended and closer to the patio. Does the specification for the French drain include the depth? Are you ever likely to make further changes like extending the patio, resurfacing or having a wall between it and the grass?


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RE: French Drains vs Channel Drains?

Yes, the drain would be much closer to the patio, specifically at the lowest point. I don't believe he listed the depth of the drain, but I can most certainly ask. Whoever i decide to go with, I will certainly have them amend the proposal so that everything that you guys suggest will be documented accordingly. With regards to assessing the area, here's a rough look at how it would look after a storm. Matter of fact, you bring up a very valid point. Next heavy rain storm, i'll go out and measure specifically where the areas are affected as well as take pictures. One other thing I should note, I do live in Atlanta, so there is Georgia red clay below the sod& topsoil.
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RE: French Drains vs Channel Drains?

Lets take a close look at the french drain proposal. Laag gave you some very good advice when he said:

"I'd rater see pvc used because if it is pitched, it will keep the water moving at a speed that would move any sediment that gets into the pipe along with the water. Corrugated is a lot more likely to vary in pitch allowing water to slow down and deposit sediment in the pipe. Corrugation slows it down on its own as well. The problem gets worse if the bottom of the trench is not graded to a consistent pitch. Many landscape crews either don't understand that, don't believe that it matters, or are more worried about getting the job done so the pipe tends to have its ups and downs. Then it eventually clogs."

One of the problematic areas for this project is at the street.

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In the graphic above I profile the likely relative grade of the sidewalk and curb. While sidewalks do get built 4 or more inches above curb grade, on flat ground the usual difference is around 2 inches as shown. A proper pipe grade (shown in blue) going downward to the gutter is blocked by the depth of the sidewalk. The cheap way of tunneling under the walk results in the pipe location shown in red. Since the slope is up to the curb, the pipe traps water that cant drain out in the area shaded in brown. During summer this will be a great nursery for mosquitoes. Over a period of time the standing water will be replaced with silt, clogging the pipe.

Remembering what lag said, lets look at the over all pipe grade.

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Here I have assigned an assumed elevation to the house floor of 100. From the photos we can see that the ground at the end of the pipe run is probably around 10 inches lower than the house elevation. We do not know what the elevation of the street gutter is, but standard house construction on flat ground usually results in a gutter grade 2 to 3 feet below floor elevation (elev 98 to 97). Suppose the pipe in the backyard is put 1 ft deep at elevation 98.2 It can be seen that if the gutter elevation is greater than 98, the pipe wont work at all. With the gutter at 98 the pipe will be laid flat, will have pockets of standing water in it, and as laag advised, will be prone to clog. If the gutter is at 97 things are only slightly better and this is true only if you follow laags suggestion for PVC pipe and great care is used in maintaining a constant grade during construction, using a laser or survey instruments. I get the feeling your contractor doesnt have this equipment nor knows how to use it.

In summery, unless you take laags suggestion to provide a direct entry for surface water to the pipe, the sole benefit of this project will be that in the days between rains the ground will tend to dry along the 3ft strip over the French drain. There will be no improvement to the temporary pooling of water and over time the pipe will be prone to clog with sediment.


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RE: French Drains vs Channel Drains?

Fulton County GA has an online GIS system. The following is a sample taken from the PDF generated and zoomed to 200% showing contours at 2ft intervals.

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This type of mapping is very useful for the design people here to understand what the situation is for your lot.

To get the graphic for your lot, go first to ...
http://wms.co.fulton.ga.us/ms/master/top.php?dir=map_generator
Find your location. As you zoom in you will see a map marked in squares with a number such as T230603. The number indicates Tile 230603.
Now go to ...
http://wfs.co.fulton.ga.us/apps/tilemaps/get_tile.php
Enter the tile number without the "T". Set the form for Topographic Map then click Generate Map.

The area will open in a PDF file. Find your location and zoom to 200%. If you don't have the means to capture the screen image you may have to sign up with abobe in order to email the screen image to yourself.


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RE: French Drains vs Channel Drains?

Thanks guys for the replies. I'll make sure to take a screenshot of that PDF and post it on here. I'll definently stick with PVC pipe. I can see what you mean with regards to the grade of the pipe. I'll definently need to discuss this with whomever I decide to use. To note, i've only contacted Landscapers for these quotes. From what I gather from you guys, I should probably contact contractor instead.


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RE: French Drains vs Channel Drains?

What is it with homebuilders? They just dont get it. With slab construction on flat ground, mere inches in grade elevation mean the difference in something that works and a drainage nightmare. You would think that responsible homebuilders would learn to do a detailed grading plan and control construction to implement that plan for this type construction. They dont. The result is a drainage problem fostered upon unsuspecting homeowners. And sometimes there is no viable fix to be had at any cost.

Enter the guys that make a living mowing grass. Its cheap to add the word "Landscaping" to the side of the truck. And there are plenty of homeowners out there desperate to fix their drainage. And from what they see on the internet and in magazines, french drains and dry wells solve these type problems. Can I say "easy mark"? In reality, for every french drain and dry well that accomplishes what was intended there are 9 that are a waste of money.

Having a lawn service fix your drainage is about like having your barber to do brain surgery.

End of rant.


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RE: French Drains vs Channel Drains?

Noted. I'll contact some contractors for the job. The red X indicates my lot.
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RE: French Drains vs Channel Drains?

  • Posted by laag z6CapeCod (My Page) on
    Thu, Mar 4, 10 at 19:43

0.2' drop in 122', pls8xx? Is that a typo?


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RE: French Drains vs Channel Drains?

No typo, laag. From the information known, the pipe grade in the rear is shown at maximum height. What is unknown is the street gutter grade. But drops of 2 ft below house floor grade are common on flat grade with slab construction. If that is the case, the 0.2 ft drop over the pipe length is the best that could be done. Looking at the contours provided by advertaddy, I would guess that the street gutter is lower, maybe around elevation 97, allowing a pipe grade of around 1%. Ill leave it to you to describe the performance at these slopes, flexible corrugated versus PVC, with and without good grade control during installation.

Advertaddy, you did good getting that graphic. Its not often we get that type of response to a request for information.

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Based on the contours, I have shaded the area that likely drains to the problem spot. Luckily, its not that big, maybe around 8000 sq ft. As you already know, common rain amounts produce pooling, but nothing that leads to house flooding. If you should get an uncommon rain of better than 6 inches, I would expect something like 30,000 gal to hit your backyard over a 2 hour period. Remember that water depth is a function of inflow versus outflow. Dividing quantity by time, you need to discharge about 250 gal per minute; an amount way more than a 4 inch pipe can handle but something thats easy to handle with overland flow. I rather doubt that you will ever experience house flooding, provided you do not let the privacy fence block high surface flow.

Turning back to the pipe proposal, I note that from the sketch and the photos, there is a water meter and line from the corner of your lot to the house. The gas meter indicates a gas line running through the project area too. Its likely that the drainage pipe will have to cross both these lines at some point. Since you dont want to disrupt the pipe grade, the other lines may interfere and need to be relocated to a greater depth. There is also a large shrub near the lot corner that must be avoided. If your contractor is unconcerned about these issues, its because he intends to hump the drain pipe over, or dip it under, the other lines without regard to the sediment blockage and diminished pipe performance that will result.

How does one know when you are getting a proposal from someone who is just going to bury some pipe and take your money? Two good tip-offs are one, the suggestion of flexible corrugated pipe on flat ground and two, the failure to break out an instrument and shoot the controlling elevations.

The contours provided suggest to me topography and street grades such that surface grading without any pipes would be a better solution. An accurate base map would be needed to make that determination.

And so I have another request for photos as shown below. Take #1 from across the street pointed directly at the house about 10 ft down from the fence. Take # 3 standing on the curb across the street and only slightly to the right of the house side as shown.

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RE: French Drains vs Channel Drains?

Will do, I will post those up shortly. Thank you tremendously guys for your help. I wanted to note that the house next to us(to the right if you look at the topographic map) has the street drain in front of its property near the right side. Therefore, any drainage from the french drain that makes it out on the street has a relative short distance to travel to make its way to the sewer. I dont know if that means anything but I figured Id throw that out there.


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RE: French Drains vs Channel Drains?

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RE: French Drains vs Channel Drains?

Well, that was fast. You are about the most responsive visitor to this forum I can recall. Up until now most everything said has been general in nature and would apply to many drainage problems.

I would like to go back to something laag said early on in this thread:

"The best thing would be to grade the property for positive surface drainage, but it is assumed that you can't do that for some reason."

He was right; that would be best. And from what I can see, it looks probable that surface drainage could be done with the advantage that larger flows would be accommodated and no pipe would be needed. It was the original grading that screwed things up and that is what needs fixing. But to prove the viability of a grading plan, more precise data will be needed, both horizontal and vertical.

A great source of horizontal data would be a lot survey if you have a copy from when you bought the property. Scan or photo it and post here. If you dont have a survey plat, you can save a lot of measuring by getting lot and house dimensions from the Fulton County Assessor site. Look yourself up at :

http://www.fultonassessor.org/Search/GenericSearch.aspx?mode=OWNER

Copy the lot graphic under "Map" and the house graphic under "Sketch"

Without a lot survey, in order to get the house correctly located on the lot we will need you to measure the distance from the back fence to the house at the corners and the distance from the east lot line at the fence corner over to the house corner. This wont result in a perfect base map, but close enough for whats needed.

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One last question for now do you have a sprit level?


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RE: French Drains vs Channel Drains?

I agree, this shows how a forum like this could work yet rarely does it get this level of participation well done all concerned.


I asked a couple of questions earlier that I see as relevant "Are you ever likely to make further changes like extending the patio, resurfacing or having a wall between it and the grass?" The existing 'patio' is concrete and falls away from the house where it meets the water that comes down the other way, as the picture show this is where the water gathers, in a little gully. A French drain at the edge of the existing 'patio' would be compromised if ever a wall was built there. If it was ever decided to dress the concrete with a more attractive face (stone, tile etc.) this would also upset the dynamic.

Also it looks to me (re latest photos) that some of the water sitting at the edge of your slab has been donated by your neighbour.


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RE: French Drains vs Channel Drains?

Thanks for the additional info. When it comes to home improvement from those like yourself that are kind enough to help, I am more than happy to provide info requested. You guys saved me some potential mishaps so far so im glad i've taken the time to research this more thoroughly than to dump some cash in to get quick fix. I have a level but its a small one and for small jobs inside of the house.
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RE: French Drains vs Channel Drains?

inkognito, my fault for not answering your questions. The answer would be "no" to all. Our back yard is pretty boring an uninspired but believe me, the previous owners made it look like a bumbling mess. We had to chop down several trees, grind stumps, & lay down sod. Same for the front as well. With regards to the patio, there was a horrible lattice/wood thing on there that we tore down. Our only real concern for the back yard is a safe space for our dog to play and to fix this nagging drainage problem. I never really put thought into it, but are you suggesting the neighbor that lives behind us has water coming into our yard? I guess that's a possibility but I've never really noticed. Might have to scope that out to see if its true or not.


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RE: French Drains vs Channel Drains?

  • Posted by laag z6CapeCod (My Page) on
    Sat, Mar 6, 10 at 6:48

Are you taking in runoff from the neighbors driveway?


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RE: French Drains vs Channel Drains?

The lot information is sufficient. But we will also need the house dimensions. Was there no house graphic at the assessors site under "Sketch". No survey plat?

Doing projects is a matter of matching resources to the situation. Before I describe things you should do, I need to know in a general way, are you a 30 year old athlete standing 64" and weighing 200, or 70 years old and getting around with a walker? Do you have someone that can assist you in making measurements and other chores? Have you done some DIY projects or do you shun anything that involves using a screwdriver?


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RE: French Drains vs Channel Drains?

No runoff from the neighbor's driveway.
I don't recall a survey plat@ closing and cant find such document in my records. Might have to dig more to see. .1449 Acres, 2504 Living area.

As far as my stats(sounds like a dating service): 28 male, 165lb, not fat but not in shape(working on it). My wife can assist me in making measurements, or I have neighbors that would be able to help. I have done DIY projects with my wife while our friend who has done contracting work for most of his life, has assisted us. The biggest project the 3 of us did was laying down sod front/back yard in the middle of June/July(something I will most likely never do again, lol). Screwdrivers are our friend. I like using socket wrenches. Are you alluding that my wife and friend can install this ourselves?
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RE: French Drains vs Channel Drains?

Grade and drainage are the foundation of all landscapes. A house built on a bad foundation suffers multiple problems and the same is true for a landscape. Would you spend big money remodeling an older home without first checking the foundation? Not smart. Yet many people go forward with expensive landscape projects without ever evaluating the foundation of grade and drainage.

My participation in this thread is pointed at demonstrating a process to assess grade and drainage. I hope to show how to gather a large and diverse set of data and summarize it in a graphical format I will call a base map. The base map can then be utilized to design grade and drainage that works. If adveraddy solves his drainage problem it will serve to validate the process.

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In the graphic above I have used the used the shape and dimensions from the assessors graphic to draw the lot boundary on a blank graph. Note that I assigned a scale to the graph of 1=20, each small square being 4 ft. In a like manor I used the house dimensions to draw the house on a similar graph and then traced it onto the lot drawing. The street and walk are added and located based on common residential development. Though I did my work on a computer, it could have been done with transparent graph paper, a pencil, and a straight edge.

So now I have an inaccurate base map. Inaccurate in that the house location is a guess, as is also the dimensions from the property line to the walk, street, and fence. But all these inaccuracies can be cured with a few simple measurements. Perhaps advertaddy can provide the missing measurements needed.

Water runs downhill. From what can be seen in the photos, I have summarized the surface flows by drawing the path that water takes with blue lines along with a shaded area where the water pools.

A temporary pool of water can form where a lot of water runs down a slope to a near flat area where it slows up. This is like what happens on a busy freeway when a patch of fog drifts across the road slowing traffic. There is an immediate backup of traffic. For advertaddys lot there is an upslope area, but in this case it appears that most all of the upslope water is cut off by his neighbors drive and flows to the street. So if this is not the reason for pooling, then there is only one other possibility; the pool area is surrounded by a perimeter of slightly raised ground.

The design of near flat areas is often limited to not less than a 2% grade; 2ft of fall for each 100 ft of distance. The reason for this standard is that only ordinary control in construction is needed to avoid dips and depressions that will pool water. Slopes down to 1% can work for small areas where the surface grade is meticulously controlled to a uniform slope and there is little upslope draining onto the area.

Surface flow, where possible, is superior to pipe flow. Its cheaper, usually handles greater flow amounts, and requires little if any maintenance. The question then becomes is there enough grade difference to design for surface flow in advertaddys back yard.

The closer terrain is to flat, there is a need for greater precision in determining ground elevation. This can be a problem for the average homeowner with only ordinary tools for the measurement, but it is not an impossible task.

To be continued


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RE: French Drains vs Channel Drains?

We have evaluated the some of the benefits and construction issues of the pipe proposal. Now I would suggest advertaddy investigate the possibility of surface drainage. Some reasonably accurate elevation data will be needed to prove the viability. To do what I propose, he will need some materials; a few 2ft stakes, a nylon string line, and a string level.

A string level is not a precision instrument and I am not fond of their use where accuracy is needed. But for short distances, and for this case particularly, I think the careful use of a string level will be sufficient. Rather than collect useful data over the whole of the project area, this preliminary study will be concentrated on only the critical grade points.

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In the graphic above I show the location of a string line that can be used to gather the information needed. Begin at point C by locating a space between fence boards that aligns with the back 6 inches of the patio. At the space between boards drive a wood screw about 1ft above ground level. Tie on a string line and stretch it out toward point B. Select a location for a stake at point "B such that the string passes over the patio near the back edge and also aligns with the jog in the house as shown.

Attach the string level at the mid point between B and C. Stretch the string tight and tie to stake B with a loop. Adjust the string height at stake B so that the string level indicates the string is level. Install stakes at A and D. Extend string lines to the end stakes in a like manner with all lines at the same level. Measure the horizontal distance for each line segment.

Begin at stake A. Measure the ground to string distance. Move 5 ft down the line toward B and take another measurement. Continue this process until you are near B.
Begin anew at B and start the 5 ft intervals from there. Do the same at C and make a last measurement at D

Record the measurements in this fashion

A-?
+5-?
+10-?
B-?
+5 -?
+10 -?
+15 -?

To correct the details of the base map, take measurements as shown in blue.


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RE: French Drains vs Channel Drains?

Thanks pls8xx for the additional info. I'll need to round up these materials and get back to you. I wont be as quick to respond as I'm tied up a few days but will certainly respond when I have everything in order. Thank you as well as everyone else for your help and detailed replies.


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RE: French Drains vs Channel Drains?

Take your time. Most of the forum regulars have been here for years. We aren't going anywhere.


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RE: French Drains vs Channel Drains?

Can you clarify points A, B, & D location? Here is a photo of the backyard around that location.


Also, is point D on the other side of the fence where the grass meets the sidewalk? So i will have to draw the string underneath the fence, right? Sorry if these are obvious questions, I just want to make sure.


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RE: French Drains vs Channel Drains?

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RE: French Drains vs Channel Drains?

Thanks!


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RE: French Drains vs Channel Drains?

I was reading this thread with deep interest when it simply seemed to END. Is there a link to its continuing discussions?
Thanks. llb


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RE: French Drains vs Channel Drains?

Threads on drainage and grade issues often end prematurely. Homeowners are seldom willing to expend the effort to provide the details necessary to fully understand the problem and possible solutions.

Additionally, problems of grade and drainage are often brought to this forum after after significant money was spent on some landscape project. Homeowners are reluctant to consider any fix to a problem that destroys the previous work.

The moral of this story is not to begin a significant landscape project without a comprehensive plan that always considers grade and drainage.


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RE: French Drains vs Channel Drains?

latelifebiker,

If you found this thread interesting you might like the one linked below.

Here is a link that might be useful: Drainage assessmant and plan development


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