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Old 03-07-2012, 09:49 PM   #1
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Please Help Me With This French Drain System!


Hello everyone! Coming upon my first spring project. Money set aside; plans to have a trench digging party; etc. (Yes, diggers hotline stuff all handled!)

So I need some help! Let me apologize up front for this being soooo long.

If you haven't followed my other posts; the short of it is: I have a lot of water in my basement. It is being mitigated by a drain at the bottom of the bilco stairs, running into a sump pump. But the stairs are a waterfall and the walls look horrible and obviously (block foundation), filled with water.

I need to address the water problem from multiple angles. I started by adding gutters to the garage that drain back to the alley, repairing gutters on the house, and extending the front downspouts.

A member on here came out to my house (very kindly and I thank him for it); and walked through some of my problems with me. He suggested a french drain wrapping from the background to a dry well at the front.

I'll lay out my plan, then my questions, then share the drawing...

1) Test drywell by digging one with a post hole digger and measuring water drainage.
2) Mark out yard for digging.
3) Dig a huge trench :-)
4) Start temporary laying pipe to work on making sure it will flow at 1 degree downward all the way around
5) Remove pipe.
6) add landscape felt.
7) add pea gravel.
8) add pipe
9) add pea gravel
10) wrap landscape felt.
11) Add some soil. (??)
12) add landscape felt (???)
13) More soil.
14) Sod.

1) How deep do I need to go?
2) How wide? (easydigging.com says 8,10, or 12)
3) How far does it need to be away from the foundation?
4) Can I run a solid pipe in parallell for a downspout, or could I connect the downspout into the french drain (research says that is a BAD IDEA). Would like to get off the city lateral (before they force me anyway)
5) I should use solid perforated pipe, holes down? Will make getting the angle of descent easier?
6) Most importantly; is all this effort worth it. I don't mean to question Joe at all... but if I need to dig out the house by hand (can't get digger into yard) to put a foundation drain in; I will. Would prefer not to?

Extra, I only have 30 to 36 inches of space to work with between the houses... my neighbor put his new sidewalk ON TOP OF his old one; and yes it is angled away from his house...

Future plans include a retaining wall in front of the garage (to allow leveling of the grade; and then a patio on the level grade.

(Edit: Link to my showcase thread: 526 Lincoln Victorian - AKA The New Money Pit )

Here is the drawing, it's very big...




Last edited by coderguy; 03-08-2012 at 08:11 AM.
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Old 03-08-2012, 01:09 AM   #2
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Please Help Me With This French Drain System!


http://www.easydigging.com/Drainage/...nch_drain.html

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Old 03-08-2012, 03:55 AM   #3
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Please Help Me With This French Drain System!


Make sure you calculate the proper size for your dry wells or you'll just be making a lake in the yard. If you can't get the volume (believe me, they can be huge depending on your rainfall avg.) arrange for an overflow to daylight. The dry well will then handle smaller showers but if you get a real "goose drownder" the water will have somewhere to go.


http://www.phillywatersheds.org/what...l-sizing-chart

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Most importantly; is all this effort worth it


Unless you have a spring welling up in your basement this well help immensely!
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Old 03-08-2012, 06:50 AM   #4
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Please Help Me With This French Drain System!


The plan sounds reasonable. Few comments:

1. The depth of the pipe needs to be approximately 1 foot lower than the basement floor slab you are trying to protect against groundwater. The foundation is irrelevant, except insofar as it gets in your way. Most people try to place the pipe just outside the footer, and if you have a T footer the pipe often ends up directly on top of the wider part of the footer.

2. It is not necessary to have any pitch on the pipe, you can lay them flat. That is usually how I do my commercial jobs. The water will collect in the pipes and flow down to the sump, which of course is at a lower level, since it has a pump in it continuously drawing down the water level. The water in the pipes flow because of the difference in water elevation between the water in the pipe and the water in the sump, NOT because the pipe itself is pitched.

3. I usually use 4 inch diameter perforated PVC pipe, schedule 40, holes down. You can also use HDPE pipe. Stay away from cheap corrugated plastic pipe, it has a bad habit of crushing under load.

4. As to the drywells in your lawn, there is no way they are going to be big enough to store roof runoff, unless you put in a huge tank, and even then they are going to drain out into the soil (that's why you call them drywells). So the water that drains out is going to end up in your perimeter drain system, putting additional load on your pump and piping. Better to drain the roof onto the ground and have it run off to the street. This can often be done using extended downspouts.

5. Make sure the city is OK with you draining your sump onto the street. Usually they are, but you gotta ask.

Good luck with the digging.
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Old 03-08-2012, 08:10 AM   #5
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Originally Posted by Daniel Holzman View Post
The plan sounds reasonable. Few comments:

1. The depth of the pipe needs to be approximately 1 foot lower than the basement floor slab you are trying to protect against groundwater. The foundation is irrelevant, except insofar as it gets in your way. Most people try to place the pipe just outside the footer, and if you have a T footer the pipe often ends up directly on top of the wider part of the footer.

2. It is not necessary to have any pitch on the pipe, you can lay them flat. That is usually how I do my commercial jobs. The water will collect in the pipes and flow down to the sump, which of course is at a lower level, since it has a pump in it continuously drawing down the water level. The water in the pipes flow because of the difference in water elevation between the water in the pipe and the water in the sump, NOT because the pipe itself is pitched.

3. I usually use 4 inch diameter perforated PVC pipe, schedule 40, holes down. You can also use HDPE pipe. Stay away from cheap corrugated plastic pipe, it has a bad habit of crushing under load.

4. As to the drywells in your lawn, there is no way they are going to be big enough to store roof runoff, unless you put in a huge tank, and even then they are going to drain out into the soil (that's why you call them drywells). So the water that drains out is going to end up in your perimeter drain system, putting additional load on your pump and piping. Better to drain the roof onto the ground and have it run off to the street. This can often be done using extended downspouts.

5. Make sure the city is OK with you draining your sump onto the street. Usually they are, but you gotta ask.

Good luck with the digging.
I find this very confusing?

This isn't a footing system, I am hoping to avoid excavating down to the footer of the house.

> Make sure the city is OK with you draining your sump onto the street.
> Usually they are, but you gotta ask.

Milwaukee has the opposite problem with this; too many people draining their sumps and gutters into the sewer laterals. (http://basementconnection.mmsd.com/)

> Stay away from cheap corrugated plastic pipe, it has a bad habit of crushing under load.

I will avoid that stuff at all costs :-)
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Old 03-08-2012, 08:38 AM   #6
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My point about the depth was that you have to get the pipe lower than the surface you are trying to protect, which is presumably the basement slab, i.e. you don't want water in the basement, so the pipes need to be lower than the basement, which usually mean about a foot lower than the slab. Some footer are wider at the bottom than the wall, this is called a T footer, it is very common. For example, the wall may be 8 inches thick, the footer could be 2 feet wide. Your pipe can go on TOP of the footer, the key is that the pipe must be approximately 1 foot below the slab. If the footer gets in the way, you just move the pipe further away from the house.
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Old 03-08-2012, 08:43 AM   #7
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My point about the depth was that you have to get the pipe lower than the surface you are trying to protect, which is presumably the basement slab, i.e. you don't want water in the basement, so the pipes need to be lower than the basement, which usually mean about a foot lower than the slab. Some footer are wider at the bottom than the wall, this is called a T footer, it is very common. For example, the wall may be 8 inches thick, the footer could be 2 feet wide. Your pipe can go on TOP of the footer, the key is that the pipe must be approximately 1 foot below the slab. If the footer gets in the way, you just move the pipe further away from the house.
So you are saying that this is a bad idea and that I should put a foundation drain in? If I were to do that; why would I do a dry well? I would tie the system into the sump pit?

I mean; I get your point, and I have asked/talked about doing a foundation drain many times. There is no ability to get digging equipment into my yard; I would be digging my house out by hand. This was a differently proposed plan that I believe is based on my water problem being due to my neighbors yards all being at higher elevation and my back yard being graded towards my house (at 4%!)
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Old 03-08-2012, 11:24 AM   #8
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I guess i totally misunderstood your post. I thought you were talking about installing a foundation drain (also known as a perimeter drain, sometimes called a French drain). Yes, a foundation drain would be an excellent idea, although I gather the digging part is trouble due to lack of access.

So let me start over. If you are not proposing a foundation drain, what is that "huge trench" you were talking about? Are you proposing to place drainage pipe on the surface or near the surface, directed to a drywell? I cannot see that accomplishing anything, since the surface water would flow into the drywell, leave the drywell via the holes in the drywell, enter the groundwater, and end up in your basement. Or maybe I totally misunderstand your plan.
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Old 03-08-2012, 01:05 PM   #9
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Originally Posted by Daniel Holzman View Post
I guess i totally misunderstood your post. I thought you were talking about installing a foundation drain (also known as a perimeter drain, sometimes called a French drain). Yes, a foundation drain would be an excellent idea, although I gather the digging part is trouble due to lack of access.

So let me start over. If you are not proposing a foundation drain, what is that "huge trench" you were talking about? Are you proposing to place drainage pipe on the surface or near the surface, directed to a drywell? I cannot see that accomplishing anything, since the surface water would flow into the drywell, leave the drywell via the holes in the drywell, enter the groundwater, and end up in your basement. Or maybe I totally misunderstand your plan.
The "huge trench" is what I used to describe digging down to place in the perforated pipe. I'm currently planning the top of the pipe to be 8 inches below grade... so probably 14-16 inch deep trench from back of house to front (according to picture).

With the drywell(s) 10 feet from the front of the house; won't that water be able to permeate into the soil/etc; instead of pooling around my foundation (all at the back of the house).

I also cannot stay connected to the city laterals forever; the guys in orange will make their way to my neighborhood and eventually tell me to disconnect. So if I do all the work of digging out the house (not completely against, but we're talking weeks of work here?); I'll tie that into the sump, and now I'll be putting even more water into the laterals. My sump currently pumps into the lateral on an exception from the inspector. But he warns in a storm the lateral could back up; flooding the basement, etc.

What do I do with the water?!?!
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Old 03-08-2012, 01:14 PM   #10
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Normally it is illegal to connect your storm drain to city sewer, which is what it sounds like you are currently doing. But it is perfectly normal and common to pump out either to the street directly, if there is no storm drain system, or to connect directly to the storm drain system. In some communities, there is a storm drain system, but they do not allow you to pump directly into the storm drain, so you pump to the street. My town is full of sump pump connections to the street, you can always tell when they are running by the flow of water down the curb or gutter.

As for your plan, if you are getting water in the basement, and it sounds like you are, there is a high probability that the groundwater table is higher than the basement. If that is the case, then directing roof runoff into a drywell, from where it will percolate into the soil, is not going to help you at all, since the roof runoff ends up in the soil, and the water table is already too high. The whole point of a perimeter drain is to allow you to draw the water table down so it is lower than the basement, which will permanently solve you drainage problem. To help out, you of course want to direct surface water and roof runoff away from your house, in your case all the way to the street where it runs away to the storm drain system.
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Old 03-08-2012, 01:20 PM   #11
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> Normally it is illegal to connect your storm drain to city sewer, which is what it sounds like you are currently doing.

That describes most of Milwaukee. My down spouts run into ridiculously old (iron?) pipes that poke out of my foundation, run into the basement and down into the basement floor (Then out to city sewer).

There is a huge movement right now to get everyone disconnected (been going on for years). I had already disconnected the front. Leaving me the two back down spouts and the sump.

I'm kind of sad here; your advice and joemama's seem to completely disagree.

Maybe I could just do the back of the house? (dig down to footing, put exterior drain, run into sump). Then run solid pipe to drywell with overflow to lawn (so overflow runs into the street?!?!).

I know for a fact I can't pump onto the sidewalk, or route under it... no real way to route water directly to the street.

Maybe I'll add some pics tonight...
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Old 03-08-2012, 02:39 PM   #12
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In most cases these problems are due to ineffective surface grading.

My quotes from some other threads:

"Excess surface water should be disposed of with grading first, surface inlets and solid pipe second, and collected to a pump third."

"The proper use of french drains is to de-water saturated soil where the saturation can't be prevented by some other means."

"What you have described starts as a surface water problem. Subsurface drainage is a bad idea and anything constructed that allows surface water to permeate into the soil is sheer stupidity. French drains have become the biggest scam of the landscape industry."

"The first step in determining proper drainage for your property should be to assess the volume of water you have to deal with. This is a function of the size of the area. You should consider all rainfall from roofs and yards, including any area on neighboring properties that flows onto your lot.
"

"It's best to do a plan view drawing of all your property. The drawing should show the location of any water coming onto yours and the size of the up-slope area as can best be determined. For legal considerations, the location of where water leaves your property is also important. In most states you may not block the natural water flow from a higher property, nor may you change the location or character of the flow as it leaves you property.
"

"Adding ground elevations to your base map will then show the route that water takes and any places where the grading is not adequate or desirable for the predicted volume of flow. The elevation at the exit point is paramount to any drainage design, as all grading and any pipes used must be above this elevation."


"A copy of lot survey or public records can be a big head start in creating the base map needed."

Should you go forward with this project as planned, you can be a big help to forum readers if you return a year or two from now and tell others what a big mistake it was. Maybe you can prevent someone else from installing one of those stupid french drains.

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Old 03-08-2012, 03:05 PM   #13
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Quote:
Originally Posted by pls8xx View Post
In most cases these problems are due to ineffective surface grading.

My quotes from some other threads:

...
Should you go forward with this project as planned, you can be a big help to forum readers if you return a year or two from now and tell others what a big mistake it was. Maybe you can prevent someone else from installing one of those stupid french drains.
Thank you for your um... suggestions.


Last edited by coderguy; 03-08-2012 at 03:26 PM.
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Old 03-08-2012, 06:44 PM   #14
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Sorry to have rained on your parade. Let me make up for it with a tip or two.

Keep all the water you can from reaching a level that makes it impossible to drain it by gravity to a discharge point. Fill and regrade for a uniform slope to the discharge point where you can. Sometimes a low foundation level precludes this method.

Never let roof water get to a ground level below a suitable discharge point. For example, build a gate affair at a house corner. Catch the roof water high up on the house by turning the downspout into a horizontal pipe running across the top of the gate (7'high) to near the property line. Turn the pipe down but stop above ground level high enough to have fall to the street or other discharge point. Run horizontal above ground elevation in a pipe hidden in a hedge to the discharge. If you don't like the hedge, build a planter high enough to run the pipe through.
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Old 03-08-2012, 07:57 PM   #15
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It is certainly a valid point to handle all surface water before resorting to a perimeter drain. However, it is not always possible to eliminate a groundwater problem, even with the most aggressive surface water management. In my neighborhood, for example, every house has a sump pump which typically runs a few days a year due to high groundwater, generally in the Spring, but occasionally due to hurricane floods in the fall. I don't know where in Milwaukee you live, but there are sections in most cities that are simply low lying and poorly drained, for which a perimeter drain is necessary to prevent flooding of the house.

I also note that it is common practice to build new houses with perimeter drains, even if they may not be strictly necessary, because it is relatively inexpensive to put them in during construction, and they work extremely well if properly designed and installed. Unfortunately retrofitting a house with a perimeter drain is much harder than installing during construction.

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