Whenever possible, we core drill the penetration point for a neat finish between the concrete floor and the schedule 40 PVC piping. In most cases these holes are cut between 4 and 5 inches in diameter.
There are homes where core drilling is not the most appropriate answer to entering the sub slab area, in these cases consideration is given to assure a professional finish around the suction point.
We create a bell shaped suction pit beneath the slab to expand the pressure field and increase the direction and range of air movement under the slab area. Approximately 5 to 10 gallons of material is excavated from under the slab.