Sump Installation Questions

Installing a sump pump on a fairly new construction home built on a high water table. The basement is bone dry except on rare ocassions when we get 4 inches of rain , I get some seepage in the cove area of the foundation wall. The basement is actually an all cement approx 5 foot high crawl space. The crawl slab sits on a bed of compacted 6 inches of gravel. No footer drains, good grading.
My questions are:
1) Since my slab sits on a gravel bed, does it matter where the sump is placed? On the rare ocassions when the water table is high enough to cause infiltration into the crawl, the water is coming from the entire perimiter of the crawl (from the crawl)
2) Stupid question, but if it does matter, what is the accurate method for determining the basement low spot. The builder did a pretty crumby job in finishing off the basement floor, so its not very smooth, so just pouting water on it and watching where it will flow, probably won't work.
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