Basement-Slab Draw Points...
Pulling gasses from the sub-slab (called sub-slab depressurization), or from under the basement floor, is a very effective technique for radon mitigation. It turns your drain tile into a sort of central vacuum system. This tile carries a great deal of air i.e., pressurized ground gasses under the floor and back to the sump crock.
If venting from the sump crock is undesirable, the drain tile can be typically accessed from any point around the circumference of the outer basement walls. The drain tile is typically located 8"-11" out from these walls, and is located 1" to 12" under the floor. Once we've accessed it and removed as much gravel or dirt as necessary to ensure an easy draw, the top of the drain-tile is cut out to allow for gasses to be pulled through the system pipe.
In homes without drain tile, a central basement slab draw-point is advised. Gravel and dirt are removed from the hole in the same way, and gasses are pulled from outer basement wall areas inward to the draw point and then up through the system pipe.