Trench percolation areas are a conventional method of disposing to ground, effluent from Secondary mechanical treatment systems . The method is also used as final treatment of effluent from a conventional septic tank where treatment tales place through interaction with the soil. The wastewater leaves the tank by pump or gravity to the distribution box where it is evenly distributed into up to 5 percolation trenches. The effluent then percolates out of the orifices in the percolation pipes into a gravel underlay, which acts both as a medium for treatment and distribution. Trenched Percolation areas can also be used in raised beds in sites with high water table or bedrock. Location and invert level of the pipework should always be determined from results of a percolation test and site assessment and designed as per Section 7 Epa Code Of Practice 2009