Sub Basement Walkout - Please Help

pgs_28

Hi

I have water under my basement slab. I have a traditional house with an 8 ft high basement and in the ground about 5 ft. The big difference in this property is that it has a sub basement walkout. The walkout is about 10ft wide, the retaining walls made out of PT wood and it even has raised garden beds incorporated. It has a drain at the bottom that leads to a sump pump inside the house. The sump pump goes off every 10 minutes or so during wet times of the year and during the winter every hour or so. The drain pipe goes into the sump pit from outside through a cutout in the side of the sump pit casing that is larger than the pipe itself. 99.9999% of the water going into the sump pit is from this cutout and not from the pump itself. The only place this could come is from under the basement slab. None of my neighbours have this problem and city officials tell me that high watertable is very, very doubtful. I even called a specialist and he agreed. Soooooooo.... everything points to this sub basement walkout. The shear size of this area must be over 100sq ft. I dug down (3ft ) close in front of the sliding glass doors exiting from the basement and still have hit the footings. But I have a ton of clay and it's wet. I'm wondering if I keep digging whether I will find weeping tile or what. I suspect the moisture is coming into this area and finding it's way under my slab and into the sump pit. Does this make any sense? Am I on the right track? Should this huge sub basement excavated area have flower beds? Should this whole are be encased in concrete so water only flows to the drain and not as I suspect, under the basement floor? I would appreciate anyone's comments re how to diagnosis this problem and how to correct it. Thanks in advance for you patience.

pipeguy

What do you mean by 'sub basement'



OK, I'm assuming you mean that a pipe from "the drain at the bottom" flows to the sump pump that is housed in a sump pit and that the hole in the sump pit, through which the drain pipe passes, is oversized. I also take it that most of the water pumped out of the pit enters not from the pipe but through the oversized hole.

So the area is 10 x 10 and it's grass between the retaining walls? And you're down three feet and still seeing the side of the footing? Right?

How far below the basement floor is the pick-up point for the sump pump? If it's less than 3 feet you should be seeing water in the hole you've dug? How 'bout it?

pgs_28

Yes you are right. I looked in the hole and there is water about about 28 inches down.... this pretty much falls in line with the pick-up point for the sump pump. Thanks for clarifying some of this.

Paul

pipeguy

Most homes will. This, in and of itself, wouldn't worry me provided however that it's not entering the basement or otherwise causing moisture related problems (mold, mildew, floor dampness, excessive humidity, etc.)

If the sump pump is running in the abscence of precipitation then you have a 'groundwater' issue. It's not likely you can resolve this without considerable expense given the topography of your lot. If it's just precipitation that is triggering the pump then you need to rectify the sources of run-off that convey water towards the house.

During a rain event of 3", an area 10 x 16 collects only about 300 gallons. The storage area created by the voids in a 6" thick layer of gravel beneath a 30 x 30 slab can hold approx. 4-1/2 times that much water. A sump pump rated at 3000 gal an hour would only run about six minutes to pump 300 gallons. If your pump is running for a minute every 10 minutes or so then it's only pumping about 50 gals at a clip. Not much water.
Whether or not you seal the area around the drain to make all the water go into the pipe, the water will still wind up at the sump pit. If in fact the water you have under your slab is a function of surface run-off from the walk-out area, then what's happening now is that rather than the water being conveyed immediately to the pump through the pipe it's slowly getting to the pump as it rises under the basement floor. Unless I had moisture problems I don't think I'd go to the expense of covering the walk-out area in concrete. Depending on how much work is involved, I might go as far as to pull up the pavers and cover the subgrade in poly. I don't think the flower beds are hurting anything. In fact, they might be helping to dry the area.

Your post doesn't actually state what it is you perceive to be a problem. What is the problem you want to fix? The pump runs too much? Your basement floor is damp or wet? Water is under the slab? The walk-out area collects water? I'm not sure what it is you want to address. If you don't want water in the walk-out area, the best solution is to cover it with a roof.

pgs_28

Thanks for the info! I was taken back for a 2nd with you question asking me what the problem was. I guess my theory was that water under the basement floor is not a good thing and that water being brought inside the house and then pumped out was kinda stupid. Plus, all this water is finding itself outside onto what is predominately clay and is probably finding it's way back. This is the city so it's not like I have many places to put it. I have hooked it into my downspouts that drain to my storm sewer but we have a disconnect program coming and this is not a long term solution. The other problem is that leaves and debris can clog the outside drain. If the water rise about 4 inches it will start coming in under the sliding glass door. Also I have 3 pumps in the pit. 2 operate off of house current and the 3rd is a battery backup. But what a pain. Plus the noise of the pump going on and off is driving me crazy even though I have insulated it. I think it is the check valve that makes most of the noise. And to top it all off, I use the walkout about twice a year. If I knew for sure that his was the only source I would even consider filling it in. I"m curious, what would happen if I didn't have a sump pump... would the water just sit under the basement floor forever? Why is this water finding its way to the sump pump under the floor and not just percolating somewhere. Again Thanks. I would really like to resolve this problem permanently and your info is really helping me move forward on this.

pgs_28

I was examining the building code and found out that when one builds a basement walk out that in the excavated area, the foundation wall must go down 4 feet. So when I walk out my walk out basement door and dig at that point I should expect to dig 4 ft before hitting the footings. Well I dug about 3 1/2 and have found no stone which would have been consistent with an area that had weeping tile. But the more I thought about it the more I realized that the area couldn't have weeping tile bacause it would be 4 ft deeper than the weeping tile on the other parts of the foundation. So if there isn't weeping tile I guess the only place for the water to go would be under the basement floor and out through a sump pump. Does that make sense? So I'm trying to think what my choices might be. One might be to fill in this basement walkout and put in a weeping tile at the right level that would go into the existing weeping tile. The other might be to encase the entire walkout area in concrete such that any water have to go in the drain pipe that leads to the sump pump. I also could maybe dig outside the permimeter of the walkout area and put in a weeping tile to hook up to the existing weeping tile. Am I just a fool and a bunch of thoughts here? Thanks in advance PipeGuy.

pipeguy

Yes. Unless you can drain the area under the floor water will continue to accumulate and potentially rise to a height great enough to come out of the sump pit.

Why not cover the walk-out with a roof struicture?

Install a sump pump in the walk-out area. Less noise in the house and water removed at the source.

pgs_28

The roof structure is simple to do and I will try that. But I am not optimistic. When I dug the hole it took a few hours and about 2 feet of the 3 1/2 foot hole ended up with standing water. NOt surprizing as the water stuck in the heavy clay soil found as escape route. So i decided to through 3 package of green food coloring into the hole thinking that if this water eventually made it to the sump pit that I would see the green food coloring. It has been over 24 hours and no sign of the green food coloring.

pipeguy

you won't likely see the coloring if the water has to be forced through through clay soil in order to get to the sump and unless there's a reason for the water to flow towards the sump - like the pump running. What're you trying to determine with the dye?

pgs_28

Thx for responding. The idea behind the food coloring is that it would confirm whether the back walkout was the source of the water or that it was just a high watertable or underground stream. If the water from this area isn't finding it's way to the sump than it's not the source of my problem and putting a roof over it isn't the answer. Although at least I won't have to worry about a piece of debris blocking the outside drain and the water eventually rising up over the sliding glass door threshold and flooding my basement. On last question... I have a basement drain that I was using to pump my sump pit water into thinking it would go to the storm sewer. I find out later that this goes to my effluent pump pit and is pumped up to my sanitary sewer line that is about 2 feet higher than my basement floor and basement washroom. Is this normal to have a basement that may be lower than the storm sewer? Thx again for all your help.

pipeguy

Run a garden hose in the walkout area and see if the pump comes on.


One has nothing to do with the other. However, a sanitary sewer that's higher than the slab could contribute groundwater.

awagner

did you ever solve your problem - I have similar problem but this appears to be with the water stream under and not surface water. thx