water in basement (continued)

No, I think the basement floor is below the level of the street -- the water has to be pumped out...

Hi,

The french drain I previously posted about replaced a sump pump. A sump pump by itself can work, but there are all kinds of "work".

I was only getting water every 3rd year or so with the sump pump.

Now that I have the french drain, I haven't had a flood for 20+ years. I'm sure there is some amount of rain that would cause of flood though.

My drain goes out thru the basement wall thru a long pipe under the lawn and thru the curb (belgian block) into the street.

If you can get far enough from the house to flow over the lawn that would probably be OK, but I'd expect to see some canals form that you might have to fill periodically.

I mean, to run one more test AFTER you cut the holes in the floor. Would definitely do that.

This is what I have now (or even a little better), but tomorrow is another rainy day according to the forcast :( My main concern is high humidity in the basement, and how it affects the wood (floor) above it.

No, I thought about this, but I would have to do it in the concrete... to my surprise the contractor doing the estimate didn't propose this... He proposed two separate french drain systems.

Correct, but for this I need enough water to collect in one place.

The water should get to the pump, under the slab, before anything is wet above. Make the sump as deep as possible. In my case, in previous house, I then hand-formed mortar into sump-liner, with multiple entry holes.

Not knowing how permeable the material is under your slab, which I'd hope is gravel, deep is the solution with the sump. Just as deep as is practical.

Depending on your local aquifers, more than one sump may be the ticket.

Does this mean a french drain inside the basement doesn't make sense? Or is it a backup thing (if the water does reach the floor)?

It doesn't mean that at all. Water won't flow freely under all edges of the floor to the sump. That's what the french drain does.

The pressure of the water against the cement causes the water to come right thru the cement. My basement used to form a puddle right in the middle of the floor without running in from the sides.

Also you don't want to go too deep with the sump pump. You'll end up trying to pump out the water table, wasting electricity.

FWIW, I think my problem right now _is_ with the elevated water table... otherwise where would water come from when there is no rain?

That certanly sounds like A problem. When my cement trough at the bottom of a downspout fell backwards so it sloped towards the house, I had a wet piece of sheetrock for a couple years.

Didn't do it any good. And I have to cut off the ruined 6 or 8 inches and replace it. It's in a corner of the room behind the fireplace and below a chair so no one sees it, but I know it's there.

When I put rocks under the trough, the area inside dried up (I think). And the trough is only ?? 16 or 18 inches long.

Well it definitely not 18 inches :(

A large area of my backyard is covered with concrete slobs. Now all this concrete is sloped toward the house. It always made me nervous, but didn't cause visible problems until recent noreaster. I will definitely have to deal with this, but I don't know if this should be my first priority right now.

If you don't have drains you will create a dry area around the sump pump. The water under your floor would rather go to the dry area then up through your floor. Its ability to do that will vary with your soil. Drains make it much easier for the water to get to the sump pump.

If you had continual problems, or if you suddenly developed a problem while your neighbors were dry, drains would probably be worthwhile. But since the problem happens every 20 years, I sure wouldn't want to spend $5000 to have them put in. (actually, that sounds cheap and I would be concerned it was too low) In fact, when you have this 20 year even it might flood whether you have drains or not, OR it might not flood whether you have drains or not.

By bringing the water up on to the basement floor or by collecting water that is already on the basement floor?

Yes, but you don't want to pump more than you have to. You can't pump a whole underground river out thru a 2 inch pipe. I was respondiing to one of the other posters that seemed to be suggesting solving the problem by just making the sump hole deeper. That might work up to a point.

To avoid communication problems in the future: "Water table: the planar, underground surface beneath which earth materials, as soil or rock, are saturated with water."

The other definition says "completely saturated"

So, you don't have an elevated water table when there is rain. You have wet ground, or maybe some more specific term, from which water is entering your house. But the water table doesn't go up with each rain and down afterwards.

Here's more "The American Heritage Science Dictionary - water table The upper surface of an area filled with groundwater, separating the zone of aeration (the subsurface region of soil and rocks in which the pores are filled with air and usually some water) from the zone of saturation (the subsurface region in which the pores are filled only with water). Water tables rise and fall with seasonal moisture, water absorption by vegetation, and the withdrawal of groundwater from wells, among other factors. The water table is not flat but has peaks and valleys that generally conform to the overlying land surface. Compare potentiometric surface. "

Does the cement run right up against the house, or is there someplace you can intercept the water with a drainage trench before it gets to you? Is there any low spot to dump the water using gravity, or are you going to have to pump it whatever you do. If you dump the water into the street, where does it go after that?

yes

The street would be the low spot (but not lower than the basement floor). I would have to brake the concrete and some asphalt next to the house, and then run the drains around the house and onto the street. Looks doable, but porobably expensive too. But I am starting to think this needs to be done before anything inside is done, since it looks more logical to reduce amount of water comming into the basement than to pump it out when it's already there...

down the street and into the sewer

Arkadiy