AprilAire Model 400 Whole House Water Saver Evaporative Humidifier uses 100% of the water that goes into the system by capturing excess water in a reservoir. Water is heated into a vapor and dispersed throughout the home before more water is added, helping save money on water and utility costs.

Model 400/400M bypass humidifiers use 100 percent of the water fed to the water panel – eliminating the need for access to a drain. The units have a capacity of up to 17 gallons per day. The 400 includes an automatic digital control that delivers the correct level of humidity based on indoor and outdoor temperatures.  A manual humidistat is provided with all 400M models for applications where an automatic control is not practical.