Gravity discharge for sump pit


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Old 08-23-16, 01:28 PM
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Gravity discharge for sump pit

Hi folks,

Finally getting back to my gravity discharge sump pit project. It has been a while and I can't post to my original thread so I am creating a new one. Here is a link to the closed thread:

http://www.doityourself.com/forum/we...ml#post2235094

Thanks Furd and AllenJ for your comments. So after reading your last two comments it seems that my approach might be possible. Furd seemed to hint that escavating down to "a point where you can bring in a pipe to that point only three or four inches above the bottom of the sump and then run this pipe in a continuous downward slope to a point of surface drainage" would be difficult.

AllenJ suggested "Carefully (not using a jackhammer or other percussive method) breaking away about 5 inches worth of footer to let a drain pipe run from the inside sump pit to the outside will not undermine your foundation then it might work as desired"

I would like to avoid any alteration of my footer at all.

Would you guys elaborate on what kind of difficulty I might run into attempting to bore a hole through the material under the footer (gravel, dirt?) then shoving a pipe into the side of my sump pit?

As you can tell I move slowly and want to anticipate challenges before 'breaking ground".

The sump pit floor is about 24in from the top of the basement slab floor. So I am thinking if my footer is no more than 12in thick then a discharge pipe pushed right under the footer would still come in 12in above the sump pit floor requiring me only to bore into the side of the plastic sump pit wall.


What do you all think?
 
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Old 08-27-16, 06:00 AM
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On second thought, an outlet pipe leaving the sump pit and immediately dipping down (or making a U shape) to go under the footer instead of through the footer will work fine. Just be sure that no part of the outlet pipe is higher than the perimeter drain tiles or pipes dumping into the inside pit (even better not higher than the pit floor) and then going downhill from there.

Interrupting the continuous downhill slope away from the house with some perfectly horizontal portions of outlet pipe is okay.
 
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Old 10-04-16, 06:39 AM
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Thanks for the Reply AllanJ! You now have me worried about running into the exterior perimeter drain system complicating my efforts. Because my sump pit is adjacent to my south (S) basement wall and that wall is above grade (i.e. a walkout basement wall), I believe the footer is 30" below grade there. My county code calls that depth out to ensure footer is below frost line. If that is indeed the case, would there be an exterior footer drain tile along that wall that I will need to deal with when attempting to bore under the footer into my sump basin?

I believe I read somewhere that if the footer along a walkout basement wall is deeper than 4" below the basement slab then a drain tile with pipe is not needed along that wall. I recall it be stated that some kind of french drain gravel field/trench without a corrugated pipe would suffice in providing a path for the subsurface water along that wall to leach out to the grass and downward sloping terrain.

Have you heard that?

Thanks!
 
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Old 10-04-16, 04:40 PM
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If you have an exterior perimeter drain then the gravity discharge for the interior sump pump pit must be a little lower as it begins it downward slope away from the house.

It is advantageous for the contents of the exterior perimeter drain to go out the gravity discharge also.

There is no way to show in advance that a gravel filled trench without a drain pipe will collect ground water fast enough to prevent basement flooding but the trench will definitely perform better if it did have a (perforated) drain pipe in it.

Whether or not there is a drain pipe in the trench, most of accumulated water must go somewhere else or be pumped somewhere else so as to leave air pockets the full length of the trench rather than have the water just sit there to soak into the soil below.
 
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Old 10-04-16, 10:09 PM
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Hi AllenJ,
I agree if there is a stone filled trench it needs to be drained, preferrably to daylight, rather than have it slowly percolate into the ground. What is confusing me is trying to logically figure out what type of exterior drain system I actually have along my S wall if any. I want to gauge what problems I might have putting in a gravity discharged pipe to drain my sump basin.

At the SE corner I do see a daylighted corrugated pipe exiting the ground a few inches below the slab height. I have verified it is the portion of my exterior drain tile that follows my E wall and then makes a left hand turn at the NE corner and follows the outside of my N wall heading about 10ft due W. I could not verify existence of drain tile further W along this N wall. It is about 9ft deep along the N wall so I conclude this is a footer drain.

1.) Would you expect this footer drain tile to continue to the NW corner and then head S to the SW corner?

2.) Unlike the SE corner, the slab in the SW corner is about 2 ft below grade and I can see no exit to daylight. In your experience, what is the likelihood the drain tile corrugated pipe stops at the SW corner and simply empties into a stone trench that hugs the entire S wall?

3.) What is the likelihood that there is a corrugated drain tile pipe along the S footer that follows the S wall due W until is tees into the southern going drain tile pipe at the SW corner?

4.) Finally how likely is it that there is a drain tile pipe that starts at the SW corner Tee and goes due S where it is supposed to exit to daylight but got buried over the years?
 
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Old 10-09-16, 05:38 PM
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Unfortunately I do not know the answers to your last 4 questions.

About the end of corrugated pipe that is open to daylight, you need to find out whether ground water comes out of it. If that end is not a low point and an outlet then it has no useful purpose and might as well be capped.

It is very undesirable to pour water such as from gutters into it where the water will pass along or accumulated against the foundation.
 
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Old 10-09-16, 09:41 PM
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Thanks again for your insight AllanJ. In determining whether ground water comes out of the SE corner daylighted drain tile I corrected the upward sloping corrugated pipe. I dug down around the pipe and back about 4 ft and removed the concrete debris that was preventing it from sloping properly.

I also did something a bit risky. I put a hose down it to see if the water would rise up in the pipe faster than it weeped out the bottom. I wanted to see if it would eventually rise to a level above the edge of the tipped up exit. It never did. After about 45 minutes my sump pump started cycling and water was flowing into the sump basin from the interior drain tile that hugged the wall I was flooding. I had never ever seen water ever flowing out of that side of my interior drain tile into the sump basin even during/after the heaviest storms.

So I now know that side of my interior drain tile works.

I turned the water off, extending a trench further out into the backyard and removed the last bit of dirt/rocks preventing the daylighted pipe from being properly sloped. There finally was a steady but small trickle of water out of the pipe for about 10min but not the gush of backed up water I was expecting.

Couple more questions:

1.) Do you think that was because very little standing water was in the pipe due to it being efficiently drained through its corrugated pipe slits and gravel pack down to the interior perimeter drain tile?

2.) Or might there be another local dip in the exterior perimeter drain tile further towards the N side of the house? (I repeated the experiment with 4gpm hose flow but nowhere near this amount was draining back out)

3.) Is there any scenario where it would be acceptable to place plastic sheeting over the top of the exterior perimeter drain tile gravel pack? (that is what i discovered existed when I corrected the upward sloping daylighted exit)
 
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Old 10-10-16, 06:17 AM
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I would cap the exposed end of the exterior drain pipe and leave things the way they are for now.

But stay vigilant about the amount of water going into the sump pump pit.

Further improvement, if not already, would be several inches of regular dirt (not sand) against the foundation with the surface sloped away from the house. If there is a thick layer of gravel and/or mulch at the surface and well above the foundation footing, against the foundation which if removed would leave a trench against the foundation, it should all be cleared away and replaced with plain dirt.
 
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Old 10-11-16, 07:04 PM
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AllanJ,

I dug back a couple more feet and found the local dip i thought might be there. My inclination is the correct the slope of what I have exposed. This exterior drain tile is about 6" below top of my basement slab. As far as i can tell the gravel only covers pipe 2" so I don't believe there is a big gravel trench against the wall from the surface all the way down to the drain tile.

I'm curious as to why you recommend capping the daylighted end as opposed to fixing the slope I have exposed. Do you think the plastic soil separator makes the drain tile useless or do you think there just might be another local dip even further back and I am just chasing my tail?

Thanks again for your insights
 
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Old 10-13-16, 06:21 AM
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After you correct the slope and the local dip, will most of the water that is collected in the exterior drain tile come out of that exposed end and then flow away without pooling up there and without going down into the sump pump pit?.

Gravel or coarse sand harbors water. If you have a layer of exposed gravel against the house, use your imagination that the gravel is not there. If what remains is a trench then you are likely to have basement flooding problems if there is enough water to overwhelm the sump pump. Rainwater falling off of the eaves or blown by the wind against the wall is supposed to run away from the house on the surface rather than rely on the drain tile. Thus the idea of having several inches of regular soil from the foundation sloping away from the house rather than exposed gravel.

It would still be better to excavate some of the exposed gravel (if any)even if you expose the drain tile, then put a layer of plastic or weed control cloth over that to keep the soil from settling down into the remaining gravel, and then fill it back to grade (final surface level) with regular soil.
 

Last edited by AllanJ; 10-13-16 at 06:44 AM.
 

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