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Old 04-03-2011, 04:36 PM   #1
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Interior Basement Drain


I want to install a interior foundation drain in my basement. I cut a hole in my slab and my footer is 6" deep. I'm going to use 4" rigid perforated pvc pipe. My understanding is that I need at least 2" of gravel surrounding the pipe. Also, the slope is suggested to be 1% of total length. My basement is 110 feet around the perimeter. That means if I slope my pipe 1/8" over 110 feet, it should be around 13" deeper at the finish (sump pit). That's obviously way under my footer. Will my basement walls collapse?

Or should I split my basement in half and install 2 sump pumps with 65 feet of pipe going to each pit? This would give a 6.5" total slope.

Or, am I way too concerned with the slope?

Thanks,
Joe

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Old 04-03-2011, 08:07 PM   #2
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Interior Basement Drain


The perforated drain pipe going out from the sump pump pit and all around the foundation should come back around and into the pit from the other side. So a 110 foot run (round trip) is 55 feet to the farthest point.

Before digging below the bottom of the footer, imagine a gentle slope from there going down but going away 3 inches for every inch down. Do not carve below this "imaginary" surface or slope. So to have the pipe bottom 4 inches below the footer bottom level the pipe has to be about 12 inches away. To have 2 inches of gravel under the pipe for a total of 6 inches below footing level the pipe has tobe 18 inches away.

I would not provide the full one percent slope requiring about 6 inches of height difference for 55 feet of run. With 3 pits spaced about the basement perimeter you can have 1% slopes towards each and just two inches of vertical variation in the drain pipe. (About 18 feet up and away from one pit and then 18 feet down to the next pit.)

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Last edited by AllanJ; 04-03-2011 at 08:11 PM.
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Old 04-04-2011, 01:51 PM   #3
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Interior Basement Drain


i don't know why I got caught up in the 110 feet perimeter. Thanks, and essentially the 2 pits hold the water until they fill, then the water moves down to the last pit that has the pump. Is that correct?

Joe
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Old 04-04-2011, 02:14 PM   #4
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Interior Basement Drain


110' is not alot for one crock. I would recommend getting one larger crock, with more volume, than two smaller crocks. A crock with more capacity is more efficient when it comes to the pumping of water.

As for the elevation, it depends on if you have any existing bleeders in the footing. If it were mine, I'd just dig to the bottom of footer, place about 3-4" of #1 washed stone, then corrugated hose set level (water seeks it's own level, and will likely only run though the stone below not the pipe) until you get within a few feet of the crock, and then drop the pipe a few inches as it enters the crock. I would consider drilling each block core while you have the trench open and allow them to drain any potential water into the corrugated pipe by using a toe drain.

So, to recap:

- Skip the extra crock & spend the money & effort on a bigger crock with a good primary & back-up pump.
- Additional rocks will have very little, if any positive effect on a good functioning system.
- No need to pitch the draintile, water rapidly finds it's own level in good draining stone.

Last edited by jomama45; 04-04-2011 at 02:17 PM.
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Old 04-04-2011, 03:23 PM   #5
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Interior Basement Drain


these are my plans. tell me if you think its good:
  1. make a 10" trench from footer
  2. lay some permeable landscape cloth
  3. lay 2-4" of washed gravel
  4. place pipe sleeve on pipe
  5. try minimal slope to sump pit
  6. lay pipe (solid 4" perforated pipe) holes down
  7. drill holes into each block
  8. cover with gravel
  9. place dimple board on wall and on top of gravel
  10. pour concrete over it
joe
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Old 04-04-2011, 04:56 PM   #6
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Interior Basement Drain


Quote:
Originally Posted by sloojoe View Post
i don't know why I got caught up in the 110 feet perimeter. Thanks, and essentially the 2 pits hold the water until they fill, then the water moves down to the last pit that has the pump. Is that correct?
If you go with two or three pits with the perforated pipes gently sloping to the nearest pit, you should have a pump in each pit.

Actually if you put a pump in only one pit, assuming you had a generous layer of gravel under the pipe at all points, the system will perform approximately the same as (actually very slightly worse than) a system with one pit and no slope to the pipes. When a pit without a pump fills, additional water will make its way to the next pit although not that fast. But this latter means that the pit without a pump is serving no purpose.
Quote:
Originally Posted by jomama45
110' is not alot for one crock.
The multiple pits/crocks are to further limit the worst case distance to the nearest pit in order for the purpose of giving slope to the pipes and also not having to dig so deep. If you had to dig ten inches for the pipe on a bed of gravel below the level of the bottoms of the foundation footings, then the trench and therefore the drain pipe has to be 2-1/2 feet in from the edge of the footing to provide enough earth bulk in between that footings don't cave into the trench.
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Last edited by AllanJ; 04-04-2011 at 05:06 PM.
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Old 04-04-2011, 07:03 PM   #7
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Interior Basement Drain


Quote:
Originally Posted by sloojoe View Post
these are my plans. tell me if you think its good:
  1. make a 10" trench from footer
  2. lay some permeable landscape cloth
  3. lay 2-4" of washed gravel
  4. place pipe sleeve on pipe
  5. try minimal slope to sump pit
  6. lay pipe (solid 4" perforated pipe) holes down
  7. drill holes into each block
  8. cover with gravel
  9. place dimple board on wall and on top of gravel
  10. pour concrete over it
joe
Sounds like a great plan, Ijust wouldn't be hung up on thinking you need to pitch the drain pipe when in reality, almost all the water is going to run through the 2-4" of clean stone below the pipe.


Quote:
Originally Posted by AllanJ View Post

The multiple pits/crocks are to further limit the worst case distance to the nearest pit in order for the purpose of giving slope to the pipes and also not having to dig so deep. If you had to dig ten inches for the pipe on a bed of gravel below the level of the bottoms of the foundation footings, then the trench and therefore the drain pipe has to be 2-1/2 feet in from the edge of the footing to provide enough earth bulk in between that footings don't cave into the trench.
Again, you'll be hard pressed to find a good functioning system that recommends pitching the draintile. 100' of draintile is a small basement footprint, and subsequently wouldn't require an additional crock IMO. Bad idea, not necessarily, but again, I'd go with one bigger crock than two smaller.
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Old 04-04-2011, 11:16 PM   #8
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Interior Basement Drain


Actually I believe that a foundation perimeter drain will work quite well with no pitch. The water will seek its level all the way around the pipe loop.

I suggest not putting a cloth sleeve or sock directly on the pipe. If it clings to the pipe, water will rely only on the half inch circular spots right in front of the pipe holes and dirt clogging this limited surface area will greatly impede the water flow.

Large capacity (say, 3 cubic feet) of the part of the pit (crock) below the level where the drain pipes enter will improve the performance more.
1. More time for the drain pipes to empty into the pit while the pump is still going (if the drain pipes got partly submerged before the pump started),
2. Not as sensitive to water falling back down the outlet pipe if the check valve didn't seal properly.
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Last edited by AllanJ; 04-04-2011 at 11:33 PM.
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Old 04-05-2011, 02:17 PM   #9
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Interior Basement Drain


I'm going to split the basement into 4 quarters with two pumps and pits. If I start from opposite sides, I can have 2 x 27.5 ft going into each pit and the same for the other pit. This way I can maximize slope and drainage. Thus enabling the 1% slope on each 27.5 ft section of pipe. And I won't dig that far under the footer. Make sense?
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Old 04-05-2011, 03:22 PM   #10
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Quote:
Originally Posted by sloojoe View Post
d I won't dig that far under the footer. Make sense?
Yes it will work fine. To repeat, if you dig just to the level of the bottom of the footer, then the pipe can be close to the footer. If you need to dig 4 inches further down, the nearest edge of the trench has to be 12 inches away. If you need to dig 8 inches further down, the trench has to be 24 inches away.
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Old 04-06-2011, 12:35 PM   #11
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Interior Basement Drain


thanks for the tips

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