Interior Basement Drain
I can't seem to find any specs on how to make an interior drain around the perimeter of my basement that would be attached to a sump pump. I have a poured concrete foundation. My questions are:
1. How deep do I dig my trench for the 4" perforated pipe to sit in?
2. How much gravel do I fill my trench with?
3. Do I wrap the pipe with drain sleeve?
4. People tell my to drill holes in the wall, but I think that's just for masonry blocks.
Anyone know the answers, website or book I could read about it.
Dig down almost to the level that matches the bottom surface of the footings under the foundation walls (never dig below that except for the sump pump pit itself).
Depending on how thick the footings are and how thick the basement slab is, you may have room to lay two inches of gravel and lay the pipe on top of that. There should be room above the pipe for some gravel as well as the basement floor slab itself. The suggestion has been made to put some weed control cloth on the ground surface before putting down the gravel, or to wrap the pipe in a layer of weed control cloth (There is probably a more correct cloth to use for this purpose.)
Lay the pipe with the perforations at top and bottom as opposed to left and right.
There probably won't be much vertical clearance to slope the drain pipe towards the pit but you can get away with having just one inch of gravel for the pipe to rest on getting near the pit.
Don't drill holes in the foundation walls.
I'd agree with Allan's info, other than you may not need the filter wrapped pipe depending on your soil conditions.
Also, beware of removing the entire interior floor trench if the exterior has huge loads against it. If that's the case, it's typical to race the lower 1/3 of the wall, or devise a method to install heavy rebar braces every few feet between the floor & the base of the wall.
As for drilling, it depends on what the current water problem/condition is for the foundation. Do you think it's merely a high water table, or surface water running down the exterior of the wall?
Do you know what the soil conditions are like?
Thanks for the tips. Next questions are:
1. Flexible Perforated Corrugated Drain Pipe or Perforated Rigid PVC?
2. I have 109 ft around the perimeter of my basement, 1 sump pump or 2 sump pumps across from each other at opposite corners in the front of my basement which is the lowest point?
I have a great game plan and will reply tonight with my final specs on the project.
I would go with PVC rather than metal.
Choose a corner for the pit so the the water can be easily pumped out and not puddle up against the foundation just outside. This depends on the grading of the land.
If you want to have two pits, one for a backup pump, nothing wrong with putting one at the opposite corner other than the reason in the previous paragraph.
Not sure whether you need two pits for the sake of volume of water. You'll need a hydrologist or geologist to help make that decision.
There's a few things we still don't know about like bleeders, exterior tile, etc......
Even if the drain pipe is not sloped well, most of the water that seeped into the gravel surrounding the drain pipes will get over to the sump pump pit, flowing under the pipe until it can find a perforation in the pipe low enough to enter the pipe by.
But water soaked into the gravel but below the level of all of the pipe perforations will stay there until the water table goes back down and it soaks back into the ground.
So you want the last few feet of drainpipe approaching the pit as low as is practical, say only one inch of gravel underneath.
If there is already a perimeter drain pipe or drain tile system just outside the foundation and it is not clogged with dirt, you don't need a perimeter drain system just inside the foundation. You would need a pit and sump pump for the outside drain pipes to empty into.
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