Malaysia's most common form of sewerage system is the individual septic tank (IST). There are an estimated 1.2 million premises with individual septic tanks in the country. Premises with a proper individual septic tank (Malaysian Standards - MS 1228 ) has 3 to 4 rectangular metal covers and is usually located outside the premises compound either at the side, rear or front. The septic tank only provides partial treatment of the sewage that flows into it and needs to be desludged on a regular basis, approximately once in two years, to ensure that it functions efficiently. IWK provides this important and mandatory scheduled desludging service.