This flow-through bypass whole-house humidification unit is low maintenance, cost effective, and is simple to operate. This unit requires good access to a return duct and drain. The humidifier mounts on supply plenum or return. The bypass carries air from the supply, through the humidifier, to the return. Standard control. No. HE220A1019: 12 gallon per day, uses Vista model No. 710 filter No. HE260A1010: 17 gallon per day, uses Vista model No. 714 filter