The Aprilaire Model 400 bypass humidifier is the newest addition to the line. It uses new evaporative technology to minimize water use, eliminate standing water and provide comfortable humidified air throughout your home. Gravity pulls water down while the wicking action of the water panel draws it back to the top, using 100% of the water delivered to the unit. Its the perfect choice for homes with septic systems, locations where a floor drain is not available or families interested in water conservation. Plus, its computer technology and innovative design makes it effortless to operate and simple to maintain. The Model 400 bypass humidifier is a high-capacity, water-conserving humidifier (0.70 gallons evaporated per hour), well suited to handle up to a 4,000 square foot, tightly constructed home.