If you have no connection to utility sewerage then a septic tank is the most efficient option. Similarly to regular tanks, septic tanks are made of fiberglass. A septic tank is a container divided into three parts with two dividing walls. Waste water passes through all three chambers and solid particles are settled. After this, waste water is directed to a filter or absorption field and after this to a layer of gravel and surrounding soil. The size of a septic tank should be approx. 0.5 m3 per person. The main sizes available are 2–5 m3. A septic tank should be emptied at least once a year and filled with clean water.