The distribution trough is an important part of the humidifier. The trough’s purpose is to deliver water uniformly onto the humidifier pad, guaranteeing effective operation. The trough is long-lasting and resistant to mineral buildup. To ensure top function, the trough should be cleaned with soap and water once a year and replaced every few years, or sooner if the trough is broken or damaged. The trough cover assembly and thumbnuts are not included.