What is the minimum liquid seal height required for fixture traps?

The minimum liquid seal height required for fixture traps is 2 inches. This measurement is crucial because the trap's primary function is to create a barrier of water that prevents sewage gases from entering the living space. A liquid seal of at least 2 inches ensures that there is enough water to provide an effective seal against these gases under varying conditions, such as evaporation or airflow that could disturb the seal. Additionally, the 2-inch height helps accommodate potential pressure changes in the drainage system and ensures that the trap can maintain its function in properly sealing against odor and gas infiltration. This standard helps maintain a safe and sanitary environment within plumbing systems.