Perimeter drain on top of footer?


What are the advantages/disadvantages of placing drain tile on top of the footer vs. next to the footing?
I ask as I am getting a lot of water under my basement the past couple of years and my sump pump runs much more frequently than it used to. Water is seeping into my sump pit via a rift which has been created just below point where the interior drain (from under my basement) is located. The point where the water is entering my sump pit is 8" below the floor of my basement. My perimeter drain is not connected to the sump pit, but rather to a drain pipe which daylights down a hill behind my house.
Of interest is the fact my perimeter drain does not appear to be capturing any appreciable water as there is not any flow out the end of the connected drain pipe. This drain pipe has adequate slope from the point it ties into the perimeter drain and I recently dug down to ensure the "tee" (perimeter drain to drain pipe) had not been compromised. It was in working order and when I ran a hose onto the exposed drain tile, the water did flow nicely out the drain pipe.
Is it possible that surface water is working its way under my footers and bypassing the drain tile (perhaps due to its location on top of the footers and not next to them)?
As noted earlier, the point where water is entering my sump pit is 8" below the floor. The drain tile (from the interior drain) is above this point. If I unplugged my sump pump, presumably allowing the water level to rise, would (should, actually) the interior drain below the basement floor and the exterior perimeter drain begin to capture the water (I understand the interior drain would feed water into the sump pit)? I believe the perimeter drain is above that 8" water entry point-- in its position on top of the footers.
The water table in my area is very high-- reportedly 19" higher than normal due to excessive precip over the past several months. My sump pump cycles more frequently after a heavy rain (once every ten minutes or so), peaking about 12-18 hours after the rain has ended and taking five or so days to return to a level where it might run once every 2-3 hours, assuming dry weather during this period. I wonder if I am partially a victim of excessively wet conditions at the moment or is there something else contributing?
My sump discharge is well away from the house and my gutter downspout extensions are buried and daylight 20'+ away. The grading around a couple of portions of the house is not the greatest, but I would have thought the perimeter drain would capture some/all of the surface water in these areas (back to my original question).
On a related note, I have considered the idea of having a pipe microtunneled from behind my property (large hill) under my foundation and connecting to the bottom of my sump pit. Assuming the technology is such that the tunneling accuracy would result in the pipe arriving at the bottom of my sump pit and not somewhere else, I can not think of any negatives associated with this strategy. It would daylight down a hill and the sump pump would then essentially serve as a safety valve in case a critter or something temporarily created a blockage in the hard pipe.
I appreciate any input related to the number of different things going on with my particular situation.
Thanks,
--Howie
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Howie wrote:

TOP BAD!! been there done that:( water can and does come from below footer and work its way thru your basement floor.
the underground drain to daylight is ideal, i would add a perforated line or two around your basement under the concrete floor for best drainage if your sump s a single point entry. this also allows drilling or snaking line ud=nder home to be not perfect location wise.
also price backhoe digging outdoors and run line under floor tearing up some concrete. you dont necessarily have to get the line to the sump pit, water finds its own level anyway. just so long as it spills out from under your home.
daylight drain is the way to go!
Been there went thru this......
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It sounds as though you have a near ideal setup. I wouldn't mess with the basement floor til later if necessary. Your perimeter tile should be in clean rock at the bottom of the footer. It is best to run clean rock a foot thick all the way up the wall. This promotes drainage a greatly reduces any possibilities of problems associated with hydraulic pressure exerted on basement walls. I have a chart someplace. The difference in tons of pressure or pressure per square foot exerted on the basement walls between clean rock & dirt sand or clay fill amazed me. The best way is to put landscape cloth down the dirt side of the excavation so in the future dirt doesn't leach into your clean rock. Very few homes are built in this manner anymore because most work is not specced and contractors eliminate this step to cheapen their bid price. Also many youngsters learning construction are working for companies working on bid jobs and never learn that this is the proper method for back filling. You've probably seen basement walls that were pushed in? Had they been properly back filled with clean rock, in all probability they would not have had that expensive to repair problem. Tract houses are never built correctly because the contractor usually only proffers a 1 year warranty and their dirt back fill is not even fully settled in that amount of time. I think in your situation that you would be in fine shape if your perimeter tile was lowered & your house was back filled correctly. Be sure to check your tile to daylight elevation. You will probably have to lower that tile in order to drain the lowered perimeter tile. If your drainage tile has a lot of fall you can slope at a rate of 1/8" per foot away from your perimeter tile til you hit your drainage tile elevation. On my house I installed an emergency sump outside the house. The perimeter tiles run to the sump & the drainage tile runs away from it. Thus if my drainage til plugs or becomes overwhelmed the sump pump helps pick up the slack.
I am wondering what the your gutter situation. Are they properly run away from the house? I run mine to below grade gutter boxes. These are open on top with a removable grate for cleaning and overflow water. I set them about 6' from the basement wall. I then run a tile away from them to my drainage tile. Actually I have 2 ea. 6" drainage tiles to accommodate the gutters & the perimeter tile.
Many times water problems can be directly related to poor gutter drainage.
Another hidden concern is abandoned field drainage tiles. I worked on one job where upon excavating the perimeter we found a very heavy source of water. Upon further excavation we found an 8" field tile that ran towards the house for a 1/4 of a mile. We were able to find an old tile map that showed the field tile. With some cajoling of the neighbors we were able to reroute the tile around the home.
Another often skipped step in construction these days is clean rock below the basement floor. I always put 12" of clean rock & a layer of insulation under the floor.
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Are your gutter downspouts run in PVC unslotted tile or perforated field tile? If run in slotted tile they could be leaching water around your house.
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