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.
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. 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. 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.