My house is approximately 50 years old and the basement has two sump pits.

One is a fairly large (24" diameter) and deep (18-20") pit that looks original to the house. I believe it's concrete like the slab or terra cotta.

The other is much smaller (12x12 square) and is fairly deep (24") with only a "dirt bottom". It's probably about 20 years old and is part of a full addition to the house.

When I moved in to the house a few years back, both were covered completely with sub-flooring. When I opened up the sub-floor, I noticed that both pits had filled with water, presumably from a recent rain.

I put pumps in both. They stay dry, for the most part, unless there is a significant accumulation of rain for a period of days. They tend to fill about 24 hours after the rain has started and then don't stop pumping out for a couple of days.

The bigger pit has two "rough" holes in the sides a few inches down from the floor. Looks like a chiseled/broken hole (about an inch in diameter) in the concrete/terra cotta. This is where the water enters this pit. On the worst occasions, this one pumps out every 30-45 minutes.

The smaller one fills from the bottom and fills fast enough that it can pump out every 5-10 minutes on the worst occasions. Probably because its capacity is small.

First question: Is there any way to determine if these sump pits are tied to a drain tile system? Would there be an obvious pipe entering the pit? Would drain tile have even been used during construction 20-50 years ago?

Second question: In the absence of drain tile, I suppose pumping out the pits at least serves the purpose of relieving any pressure underneath the slab. It may not be the ideal design, but it should promote drainage of water in the area and protect the basement to some degree. Is there any way to make these pits more effective? For instance, should I knock a few more holes in the sides of the larger pit to allow more drainage in? Should I deepen or expand the diameter of the smaller pit?

Thanks. Will try to post some pictures later. Please let me know if there is a better forum for this post.

 

Is the water table that high there or is there something else that can be done to eliminate the need for those pits?

 

Hard to say...

I always thought it was more of a drainage thing, but I've got all of my leaders piped 75' from the house to the storm drain (spent a summer just digging trenches for 4" PVC). I've graded as much as I can with the small yard I've got. Maybe a couple of other small things, but I've got to think it's a 'water table' issue now. Only after a real hard rain do they fill and about 24 hours after it starts.

 

If the pits are filling from the bottom or sides, then I would say there's a high water table. If you see water running into them from under the flooring, then I would try to seal the foundation with a membrane.

Your local building dept. would be able to tell you where the water table is. Do you have any objection to asking?

 

Some pictures...

The bigger sump pit:


The "hole" that lets water in to the bigger sump pit:


The smaller sump pit:

 

From what I can see in the pics, it looks like a high water table. If the pits never overflow, I'd leave it alone. I wouldn't modify it.

 

look for pipe(s) entering the sump when its dry,,, no idea about 20-50 years ago

more holes can't hurt.,,, modern sumps are solid & we drill 30 3/4" holes into the brm & 1/2 up the sides to allow ground wtr easier access to the pump.