Septic Tanks Must Be Kept at a Safe Distance from Wells – Here’s Why

Proper placement of septic tanks in homes must be carefully planned, especially in relation to clean water sources such as wells. According to Indonesian National Standard (SNI) 2398:2017 on the design of septic tanks with advanced treatment, septic tanks treat domestic wastewater before it is directed to a soakage system or further treatment. If installed incorrectly, waste from septic tanks can seep into the ground and contaminate daily water sources. The standard recommends a minimum distance of 10 metres between septic tanks and clean water wells to reduce the risk of bacteria, viruses, and pollutants entering groundwater. Additionally, septic tanks should be positioned lower than the water source to prevent wastewater from seeping towards the well. Soil type must also be considered when choosing a location; highly porous soil can accelerate contamination of groundwater, requiring more careful waste treatment system design. Septic tanks must be constructed to be watertight to prevent leakage into the ground, with strong walls and base to resist seepage. They should also include advanced treatment systems such as soakage wells or infiltration beds to filter liquid waste before it is absorbed by the soil. Ventilation pipes are essential to release gases produced during waste decomposition, maintaining stable air pressure and reducing unpleasant odours. Endra S. Atmawidjaja, Chairman of the Indonesian Association of Health and Environmental Engineering Experts (IATPI), stated that ventilation pipes help prevent septic tank explosions. Methane gas accumulates in septic tanks due to their anaerobic nature, lacking free oxygen. ‘Often, the issue is a lack of ventilation or vents being blocked by soil or other materials, trapping the gas,’ Endra told Kompas.com on Tuesday, 26 May 2026. When methane levels exceed 15%, it can cause explosions; normal levels should stay below 5%. Another crucial point is ensuring septic tanks are accessible for regular sludge pumping to maintain optimal capacity and proper functioning of household sanitation systems.