An insecticide using method is applied to a drainage system of a building, to remove the pests which breeds in a pipe of the drainage system. The insecticide using method including: mixing water and an insecticide, to form an insecticidal foam and an insecticidal liquid pouring a part of insecticidal foam and a part of insecticidal liquid into the pipe of the drainage system before the part of insecticidal foam and the part of insecticidal liquid completely flows into the pipe of the drainage system, pouring other part of insecticidal foam and other part of insecticidal liquid into the pipe of the drainage system.除蟲劑的使用方法是應用於建築的排水系統,以去除從排水系統的水管中孳生的害蟲,除蟲劑的使用方法包括:將水和除蟲劑攪拌,以形成一除蟲泡沫和一除蟲液;將一部分的除蟲泡沫和一部分的除蟲液倒入排水系統的水管;在該部分的除蟲泡沫完全流入排水系統的水管之前,將另一部分的除蟲泡沫和另一部分的除蟲液倒入排水系統的水管。20‧‧‧除蟲泡沫30‧‧‧除蟲液90‧‧‧漏斗100‧‧‧建築200‧‧‧排水系統210‧‧‧水管220‧‧‧污水池300‧‧‧害蟲
