Scale Control Insert for 350/360 Models

The Aprilaire Scale Control Insert 4181 is the u-shaped component which encases the Water Panel. The Aprilaire 4181 scale control insert is commonly called a filter/pad frame. It is located on the inside of the humidifier, and surrounds the water panel. The purpose of the frame is to prevent mineral build-up inside the humidifier cabinet, and divert excess water to the drain. The scale control insert should be replaced every five to eight years - sooner if it is cracked or damaged. This item is also available as part of the maintenance kit for your model.