Help with Sump Pit!

BalanBro

Hi all, and Merry Christmas! I certainly didn't want to talk about this today, by my sump pit installation hit a major snag yesterday. I have an old finished basement which gets some water in it during heavy rains. The problem is isolated to one wall, so I decided to install a sump pump next to it to help alleviate the pressure.

I started my removing a section of my tile floor which came out nice and neat. Then I used a jackhammer to break up an area for the pit and brought it up to the cinderblock wall that leaks (which I was planning on drilling weep holes to drain into the sump). A while later, we started digging, and this is where we got stuck. After diggin into dirt just a few inches, we hit what seems to be a large, continuous and irregular rock . It coves the entire area of excavated concrete, which is a good 3' x 3.5' wide. It is very rough, in that the height of the rock varies all around, so it's difficult for me to tell what it is. Part of me wants to just pass the jackhammer through and see what happens. I just don't no what it is or if it's perhaps structural. Any thought's on what this could possibly be.

Daniel Holzman

Post some pictures. That could be part of your foundation, in which case jackhammering it into submission would be a very bad plan (VBP). You may want to relocate the sump pit further from the wall. If you have gravel under the slab, there is no reason to put the sump pit immediately adjacent to the outer wall.

BalanBro

Thanks for the reply, Daniel. I'll take pics ASAP. What gets me is that I should be far enough away from the footing to at least be over dirt. There's no gravel underneath, rather it seems as there is a thin layer of dirt sandwiched between the concrete slab and this strange rock. I'm kind of wondering if I could leave it alone and make this into a shallow sump pit. Unfortunately its only about 8-10 inches below the top of the concrete slab.

Bondo

Ayuh,... Any chance yer lookin' at Bedrock,..?? a ledge...

It happens alot 'round here...

Daniel Holzman

It would help if you post your location. That could be a random rock, if you live in glacial till country there are often random rocks. A shallow pit will do you no good, the pump bottom needs to be at least four or five inches below the shutoff water level, if you use a six inch drop on the float, and want the pump to turn on four inches below slab level, you need a pit at least 5+6+4 = 15 inches, most places recommend 18 inch deep minimum.

BalanBro

I'm in northern NJ, Bergen county.

BalanBro

BTW all, I just wanted to say that this is a fantastic website and i wish I found it sooner. Is there a way I can find a trusted contractor though this site? I feel that I may be in over my head at this point.

BalanBro

Here are some pics. There's some dirt on top so it may be hard to see. It's difficult to remove the dirt because the rock underneath prevents me from using the shovel. The middle of the second pic is an area i cleared away to show what's under the dirt. As I said, it is very uneven (not planar at all).

Bondo

Ayuh,... Clean it up better, 'n decide whether it's bedrock or not...
Ya might have to use a small broom, 'n dustpan, or Whatever...

If it Is bedrock, you can drill, 'n hammer out enough to create yer pit...

I'm guessin' it is, as it makes no sense that it's concrete...

BalanBro

So get this, I was cleaning out the area with a wire brush and small shovel to take a better picture, and found a hole where there was no rock, about 5" diameter. So I took a mallet and a cold chisel to knock off a chunk of this "rock", and sure enough it was concrete (mixed with gravel). Apparently, under my concrete floor is a small layer of dirt followed by a second rough patch of poured concrete. It's not very thick; I'd say about 2-4 inches with varying thickness.

I did not want to bring out jackhammer, so I just continued to open the hole with a 3 lb mallet and cold chisel until I was finally able to fit my enourmous 26" diameter liner with 3-4 inches of clearance all around for river rock. It took me all day with the hand tools and backbreaking digging with all the stone down there, but boy do I feel accomplished! Tomorrow will be the plumbing, filling in with more river rock, and finally drilling weep holes in the adjoining foundation wall. Admittedly, I am doubtful that I'll even get enough water in there for the pump to turn on, but it should at least be effective in releaving some of the pressure on the foundation wall.

AllanJ

You may eventually need some way for water all along the outside of the foundation to get to the pit.

At some time in the future you may end up laying perimeter drain pipes (a French drain). This 3 to 4 inch perforated pipe has to pass either over or under (or through) the concrete slab to reach the pit. If the drain pipe passes over, the entire drain pipe has to be no more than 8 inches below floor surface level. This actually should be deep enough but that is not guaranteed to eliminate flooding at the far side of the basement.

One advantage of an extra large pit is that, if the check valve on the pump outlet fails, the amount of water falling back into the pit is a much smaller fraction of the pit volume so that no problem is caused.

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