My place currently has a small (1 cubic foot?) pit in the basement floor with a sump pump in it, sufficient to catch the occasional flow across the basement floor from the (not well sealed to the foundation) bulkhead space. This pit is concrete lined, and there are no perimeter drains; it really is there just to drain water already on the floor.

shallow sump pit, overkill pump...

Except for serious flood conditions, this is just handling an occasional trickle. At the worst (100 year flood), the pump was running at about a 50% duty cycle, maybe 8 gallons per minute.

I'd rather not have water above the floor at all, even when the water table is at its highest.

So my question: would simply turning this into a real sump (porous barrel below floor level, hopefully punch only one large hole in floor to drop it in) draw enough water out from under the foundation to prevent infiltration even in bad conditions, or would I need a full system of peripheral French drains to achieve that (much more cutting/repair of concrete)?


There are two infiltration points, both of which I have attempted to seal with spray foam to be followed when I have time by hydraulic cement. (Tried an injected epoxy filler but didn't have great success with it.) One is where the bulkhead stair enclosure -- cinder blocks -- meets the poured foundation; this seeps slightly even in a "normal" heavy rain, resulting in a puddle coming in under the door. bulkhead door enclosure, seen from inside basement The other, which I've mentioned before, is between the structure reinforcing the back wall of the original brick-over-fieldstone foundation, and the new poured foundation of the extension. This too is a cinder block structure apparently not sealed to the poured wall. Leakage is alongside or under the cinder blocks -- from the corner, anyway. cinder block bulkhead supporting bottom of old foundation back wall I should note that I've never seen leakage through the brick-over-fieldstone foundation, probably because the extension's basement is a good foot deeper than the original.

Local soil is moderately sandy, I think. But this is New England; there may be glacial erratics or other Big Rocks anywhere under the concrete floor. (All our picturesque stone walls are really the result of many years of farmers dumping the annual crop of rocks at the edge of the field...)

Hope that helps. I agree that belt, suspenders, and skyhook is probably the right answer, but if it would make sense to try something simpler first... This is rarely an issue and almost never a problem, but I would like to reduce that "rarely" and "almost" on principle. A house is a tool, and tools should be kept sharp.

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    How is the water entering the basement? Is it something which could be sealed? Or diverted? Could you change whatever source of water is feeding the basement walls? What kind of soil (clay, rock, gravel, loam sand, etc.) is outside?
    – wallyk
    Aug 17, 2016 at 19:48
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    You could bet on it helping, but "how much" and "would it keep the floor absolutely dry" would depend utterly on what's under the slab and where the water comes from. Clean stone - looking good. Clay - not looking so good. Large diameter does not really do a lot in a sump (increases storage volume, yes, but either you are pumping or you are flooding), so you could keep it near the same size (if you wanted) and just punch it deeper. If it actually has a concrete bottom, you could even leave its ~1 foot sidewalls and just break out the bottom and then keep going down.
    – Ecnerwal
    Aug 17, 2016 at 20:48
  • Picture of the 'drain' ?
    – Mazura
    Aug 17, 2016 at 21:14
  • Larger sump volume may reduce the on/off cycling frequency of the pump, and maybe wear thereupon , but since I am hoping the sump would stay dry most of the time... There is also the question of what any of this would do to radon levels, assuming there is some.
    – keshlam
    Aug 18, 2016 at 1:34

2 Answers 2


I wouldn't think that even in bad conditions the water table rises all that much, I'd guess your infiltration is from the side walls as rain drains down into the earth. Re-grade next to the foundation.

If that doesn't help, then yes, you need a real sump. I'd need a pic to say if I'd make a new hole or not. French drains can be added later, but you'll need a sump regardless. Or not, if re-grading takes care of it. Order of attack:

  1. Re-grade next to the foundation

  2. Add sump

  3. Add French drains

If you're serious about keeping it dry so you can use it as a rec room or whatever, arbitrarily do all three steps.

Seal the foundation with some caulk and paint it. Or skim coat the whole thing and then paint it. At the very least, some paint will show you where the trouble spots are once they discolor. If there is space permitting, I'd leave that old pump alone as a backup, and dig a new pit if you're going to put a new sump in.

But if you're 5~6 feet above a river, a real sump pump might be a losing battle... Caulk the wagon and ford the river.

  • @keshlam - 80' from a stream? Yikes. Your foundation may be acting like a boat; you might not want to punch a hole in your sump-drain pit, and instead take a look at sealing the foundation. - Suck all the water out of the pit and drill a hole in it. If water starts rushing in, you might be looking at having a pump run 24/7 if you do install a real sump. Which would explain why it's concrete lined in the first place...
    – Mazura
    Aug 17, 2016 at 22:55
  • May be mis-estimating the distance, and the stream is normally 5-6 feet below ground level at the house, but.... The basement, as I say, is mostly dry (modulo the usual basement humidity) save for a trickle in heavy rain, so I am assuming the usual water table is below me.... But may not be far below me. Wonder if there is a town office which might know that.
    – keshlam
    Aug 17, 2016 at 23:43
  • I agree that re-gradng is always the first step, and I've been working on that. Just trying to consider all the alternatives and decide whether I want to ask my contractor for a quote or just reseal and see what happens.
    – keshlam
    Aug 17, 2016 at 23:46

I would not bust the concrete under the sump to go deeper,i would lay tile around the outside of the house and have it drain off. I would think about a curb around the basement inside and drain to the existing sump.

  • I would consider setting up a water pump and drain the sump area by pumping the water back outside. this would set you up in case you have a bad year of rain.
    Feb 12, 2018 at 0:28

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