Percolation tests only let you know if you need a raised bed for percolation area or not, you will still have to buy a sewerage treatment system, be it Bord na Mona, Bio-cycle or one of the other systems. Essentially if your site passed the percolation test, you can install the percolation system straight into the ground, otherwise you have to build a raised bed with suitable graded soil to house the percolation system ( series of wavin pipes with perforations in them and a french drain system)