Sump Pit with Drain Tile - Holes in Liner

[chihotdog13]

Hello, I had a question about having holes in a sump pit liner. I read lots of threads here already, but think my situation may be slightly different.

I have a very minimal amount of water coming in on one side of basement foundation, in one specific spot. I believe it's due to hydrostatic pressure, as there is a small joint where the slab and wall meet, and it seeps out of there. Nothing comes over the top of the wall.

I was planning on using WaterGuard system, which is drain tile that goes on top of the footer, and then cement over it.

I purchased an InstaSump Pit basin (https://www.instadrysumpkit.com/) which I know is made for crawlspaces, but since there is so little water coming in, I figured I didn't have to dig down deep. The basin is more shallow than others (14" deep vs 22/24" deep standard basin). A reseller stated it would be a good fit when I wrote them what I described my situation is. But, now, I am re-thinking now that I have the slab opened up.

The problem is this pit basin has 4" slots all over the pit so that water can come into it--similar to drilling holes in a solid liner. However, since I have so little water, I feel like it will not work for my scenario, as I don't have large amounts of water coming into the basement (and of course, I don't know what happens below the slab since I had not had it opened up for digging). I feel like if water comes into the pit from the drain tile, since a little amount will drain out of the basin into the surrounding substrate. From other threads here, holes are good to allow water to come in/not have the liner float up.

Should I be using a traditional pit liner with no holes under this circumstance, or a traditional liner with minimal holes drilled 12" or more up on the liner instead of the InstaSump one?

 

[Reach4]

As you can see, opinions differ. I would prefer holes up higher. No sense trying to lower the ground water level for the neighborhood.

In service, to keep the sump from floating up, I would have the top of the sump fixed in mortar. I would have pea gravel around the outside to allow water to move. I would tend toward 3/16 holes to exclude gravel.

If there is water trying to float the sump before you get it cemented in place, consider filling the sump with water to weight it down. I am not a pro, and I have put in exactly one basement sump.

 

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[LLigetfa]

No sense trying to lower the ground water level for the neighborhood.

That's not how it works. Google cone of depression.

Dig the hole for the pit to see if you hit the water table. With a shallow pit and no holes, there is a chance the pump will do a lot of short cycling. For sure you will need a sump pump with flexible level sensors as traditional float systems don't work well with a narrow range.

I changed over from a submersible sump pump to a pedestal pump so that I could tweak the float to get more than one minute runtime.

 

[chihotdog13]

I just wasn't sure if I should use the shallow pit i purchased with a bunch of slots in it, or the traditional, deeper pit. The amount of water that seeps is only during large rains. We had a rain here a year or two ago for about 2 days straight, and I had a puddle on the ground in one spot, maybe 1/8" high by 1' wide and 3' long.

If it rains moderately for a day, it occurs in the same spot but much much less. I was trying to not have to dig down very deep, but agree i need to dig down to see if I hit water where the pit will be.