The text explains methods for detecting defects in household drains and sanitary fittings, outlining practical tests to locate faults that can harm occupants' health. It analyses sewer ventilation, critiques common construction mistakes by architects, builders, and surveyors, and considers how poor drainage can contribute to the spread of zymotic disease. The author describes using instruments such as a detector and anemometer to trace ventilation failures and diagnose sources of sewer gas and malodour. Practical recommendations are offered for improving installation and inspection practices and for persuading local authorities and property owners to adopt more reliable sanitary measures.