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Discussion Starter #1
Considering installing french drain inside of basement. The slab is 2" thick and the walls are block. Al of the articles, research etc... I have read have said to cut the slab about 12-18" from the block wall install the piping and reconcrete over everything but leave a small gap next to the block wall. Does the slab provide any significant reinforcement since the block wall will now not be touching the slab. This tiny gap is ok? Thanks.
 

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2" does as jomama sez,,, when wey open the floor, floor slab sits on 4" of foundation ( 16"wide less 8" block/conc = 8"/both sides of the wall (4") the rest of the trench width is because we use shovels that measure 10" wide,,, many diggers have issues trying to remain within such tight dimensions hence 12" actual typical width,,, anything less & you're using a plumbers shovel ( so named because they get paid by the hr so taking longer brings in more dinero )

ask jomama to post his link to a neat diagram - he'll do it as he's a fairly decent fellow - or so i've heard
 

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Discussion Starter #5
jo, according to stadry's response he says you have a diagram for interior french drains. If you would what is the link. Thanks .
 

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Do not excavate at the foundation footing deeper than the bottom edge of the footing. Progressing inward (outward for an exterior perimeter French drain) you could go down further gradually, no more than one inch down for every additional 3 inches away from the footing.

Provided that the slab was cut squarely, after you reconcrete things when done the new concrete will provide the same lateral support as the original slab did.
 

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good point, allan, but wtr seeks its own level & rushes to fill a void,,, nevertheless, its wise to NOT excavate below the footer's btm,,, as wtr collects in the pipe, it will run out into the sump only to be replaced w/more collected wtr - wtr rushes to fill a void ( try making a hole in a tub full of wtr )

as a genl rule, 1 zoeller m-53 pump will serve 100' of pipe - over 100', plan on 2 - depending on amt of wtr of course
 

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Discussion Starter #9
Thanks stadry for the links. Will have some questions concerning details. Thanks for the help.
 

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jo, according to stadry's response he says you have a diagram for interior french drains. If you would what is the link. Thanks .
Go to the link I provided above in an earlier post, click on "Resourses", and then "Wet Basements 101" and it will take you to a few videos about what you're likely dealing with. That site has quite a few informative videos & "Hyperspecs".........
 

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g, either he's still asleep or ****ed off & not the decent fellow i've heard he was,,, try these til he either wakes up or changes his attitude :surprise:
:laughing:

Neither banned or sleeping! As a matter of fact, I've been up since 4:15, as my 4 YO daughter is in "nightime potty training mode" and turns on all the lights in the house when she gets up to go. She woke me up & I couldn't fall back to sleep!
 

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Discussion Starter #12
Stadry or whomever wishes to reply. Finally began to test a portion of the concrete floor. Thought the footing would not be 8" deep. What I have is about 5 1/2" deep and a 4" ledge back to concrete block. The slab is approx 2" thick. After looking at several of the diagrams most of them showed stone underneath the 4" pipe and some on top of the pipe with the stone level with the top of the footing followed by sheet drain. A few questions.

1) Some diagrams showed stone underneath the 4" pipe only with the pipe even with the top[ of the footing with sheet drain, poly and concrete. Ok to lay only 1" or so of gravel underneath pipe and have top of pipe level with footing no stone, sheet drain, poly and concrete directly over pipe? Switch to 3" drain?

2) Have read several times do not excavate below bottom of footing. Planned to locate sump pump basin in corner. The basin is much deeper than the footing depth of 5 1/2". I assume in this instance it is ok to go below the footing? Also, how far out should the basin be from the corner walls? The basin will receive water from each length of wall. Two pipes entering basin.

3) Pitch- recommended 1" every 10 feet- many others have disagreed and said it is not necessary. If the 5 1/2" footing depth could work still no need to slope? Also, not sure if footing is level may go up or down in certain spots. Would basin need to be moved because of this? Basin can really only go in the corner. Read max distance from discharge line to outside is 15 feet?

Thanks for your help.
 

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Stadry or whomever wishes to reply. Finally began to test a portion of the concrete floor. Thought the footing would not be 8" deep. What I have is about 5 1/2" deep and a 4" ledge back to concrete block. The slab is approx 2" thick. After looking at several of the diagrams most of them showed stone underneath the 4" pipe and some on top of the pipe with the stone level with the top of the footing followed by sheet drain. A few questions.

I would literally do a little more "digging" and ensure that the footings are really only 5.5" deep. It very well could be that they formed them with 2x6's, but the footings were poured closer to 8". I see it quite frequently.

1) Some diagrams showed stone underneath the 4" pipe only with the pipe even with the top[ of the footing with sheet drain, poly and concrete. Ok to lay only 1" or so of gravel underneath pipe and have top of pipe level with footing no stone, sheet drain, poly and concrete directly over pipe? Switch to 3" drain?

This is how we have always done every repair, and we used to do every new construction installation. We still would if we didn't use "Form-a-Drain". The stone underneath is more important than over.

2) Have read several times do not excavate below bottom of footing. Planned to locate sump pump basin in corner. The basin is much deeper than the footing depth of 5 1/2". I assume in this instance it is ok to go below the footing? Also, how far out should the basin be from the corner walls? The basin will receive water from each length of wall. Two pipes entering basin.

99% of the one's we've installed and I've seen installaed are very close to the wall and/or corner. I suppose there's a possibility of "scour" from doing so, but I've never actually seen it around a sump crock. We generally have very heavy clay here though.

3) Pitch- recommended 1" every 10 feet- many others have disagreed and said it is not necessary. If the 5 1/2" footing depth could work still no need to slope? Also, not sure if footing is level may go up or down in certain spots. Would basin need to be moved because of this? Basin can really only go in the corner. Read max distance from discharge line to outside is 15 feet?

Thanks for your help.
I've never heard of pitching an interior or exterior footing draintile system, other than the internet. In my career, I've installed hundreds (maybe 1000's now) of draintile systems, fixed a lot of existing, and I've yet to see one of them with obvious pitch. As long as the Earth contines to orbit on it's axis, water will seek it's own level. If the Earth stops rotating, we have alot more to worry about than damp basements.

I can't see why you would have to limit the discharge line to 15', never heard that before. The most important factor is lift, and once you get over that, as long as there's a slight pitch to the hung pipe, the rest offers very little resistance against the pump. I've got probably 35' of pipe on my pedestal pump before it get's outside, and that pump runs a fair amount and it's at least 10 years old........
 

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Discussion Starter #14
The install for the basin would be in the corner of the basement. One pipe entering from each wall. Will be using some drainage sheet as you had suggested along the base and extending up the wall a bit. There is some leakage coming down the wall exactly in the corner of the wall. Once the water goes behind the drainage sheet in the corner there is not a direct way to enter the drain pipe or basin. Plan to install the basin with some type of gravel around it not sure if gravel should be underneath the basin as well. Assuming the water from the corner will drain around the basin and would have to fill around the basin and then reach the drain pipes on either side and then drain into the basin. Is there a more direct route for the water to enter the basin? Thinking of drilling holes around the basin maybe half way up so it can enter there as well? Also, read that some drill holes all the way down to the bottom as well trying to remove as much water as possible under the slab. Concerned there will always be some water at this point and the pump will run non stop. Thanks.
 

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we ALWAYS use a 1" spade wood bit to drill holes in the bottom AND side of the crock,,, line crock excavation w/soil filter cloth, clean #57 stone under the crock, install crock, then add 6" 57 around basin's circumference,,, wtr flows out of the wall under the waffleboard then down into the trench,,, block wall needs 3/4" drainage holes in ea cell + web
 

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The purpose of holes in the bottom of the basin (crock) is to keep the basin from floating up out of the hole, possibly tearing apart the pipes.

A disadvantage of holes in the bottom of the basin is dirt possibly getting in and, over time, clogging the pump.

It is possible and acceptable for there to be several inches of water for days or even weeks and stay that way provided the level does not get too high. When the pump finally starts, it should keep going until the pit is nearly empty.

The pump will not run continuously unless water is pouring into the pit really fast.

Suggested starting level where the pump turns on, when the water is a little way above the bottoms of the 4 inch drain pipes.
 

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drainage systems aren't no maintenance items,,, from time to time 1 should look into the sump + flush out the collection pipe (that's why we install cleanout at system's midpoint ( if poss ),,, ships float because they don't have holes in the bottom - same w/crocks,,, no seepage holes = poss floating crock & poss discharge line damage

suppose in a VERY silty soil 1 could experience pump clogging but we generally only find that w/ext pumps when grading washes surface dirt into the sump,,, we use pump stands under our zoeller m-53 pumps,,, make certain you provide a 1/8" drain hole under the ck valve too,,, there no adjustment on a pump for 'where' it starts pumping to my knowledge other than tieing down the tether or putting bricks under the pump
 

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Suggested starting level where the pump turns on, when the water is a little way above the bottoms of the 4 inch drain pipes.
I wouldn't put too much thought into the height the pipes enter at. There's really not much "rhime or reason" as to what height the pipes enter into the crock, so the advice is pretty generic. We generally dive the interior draintile down relatively quickly at the sumpcrock, but there's no standard height that they really need to be at, other than no higher than the rest of the draintile in the basment.

I've said it many times in the past, but I'll say it again. Most of the water in an interior draintile system doesn't even run through the pipes themselves. It drops out of the pipes faster than it drops in, and tends to run in the stone under the pipes as it seeks it's own level. I think too many people try to apply the same logic to perferated pipes as to soild drainage (sewer, etc) pipes, which couldn't be farther from reality.
 

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Discussion Starter #19
Jo and stadry,
Excavated near the interior footing of the basement and the footing is not a consistent depth. Some areas around 5 1/2" and others 7 1/2" or so along the same wall. Questions:

1) Using a 4" pipe for the 5 1/2" footing really no room for it. Plan on using 3" black corrugated pipe. Ok?

2) Trench is about 12" wide. If the 4" pipe is really that much better than 3" would consider trying to have the trench go at a 45 degree angle from the bottom of the footing and lay the pipe further out from the footing. Would the 45 degree angle be correct in keeping with the rule of not going below the footing? Really do not want to do this if the 3" pipe is sufficient.

Thanks for all your help and others that responded.
 
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