Humidifiers: Drum Style vs. Flow Through

To thoroughly understand the comparison of flow through vs. Drum style humidifiers let’s start with similarities. Both the drum style and flow through humidifiers use a by-pass duct. (Fan powered flow through units are available but are only used in very tight installations) The bypass duct allows the high pressure high temperature air from the supply plenum to pass over the moist media, transfer to the return air duct and increase the humidity in your home. Many times people will talk about the optimum place to mount a humidifier, on the supply plenum or the return air drop. Theoretically either place is the same. The bypass duct connects the supply to the return and air only travels from high pressure to low, either way moving air across the moist media.

Flow Through vs. Drum Style Humidifiers

The primary difference is not visible. On a call for more humidity, the flow through humidifier valve is energized and opens allowing water to flow vertically over a media, as the water trickles down some is absorbed into the air stream while any remaining water flows directly through the humidifier to a drain.

The drum style humidifier has a reservoir which stores a small amount of water. The drum, which is surrounded by a sponge like material, is set with the bottom of the wheel slightly in the reservoir. A small float resides in the reservoir, sensing the depth of the water and maintaining a specific level to ensure the water is picked up by the pad. Upon a call for humidity, the drum begins to roll and air starts to flow across the drum to add moisture to the air. Because there is a reservoir and a float, no water flows out the bottom and any drain would be for precautionary measures and not function.

Benefits of Drum Style and Flow Through Humidifiers

The benefit to the flow through humidifier lies on the fact that no water is left standing until the next time you need humidity. With a drum style humidifier, the water is always standing for a period of time allowing for a variety of bacteria to grow and be distributed to the home. Drum style units can be a source for or distributor of a variety of illnesses. The benefit of a drum style humidifier is that no drain needs to be run. All of the water will stay in the unit and get distributed to the home. The downside to the flow through is there is a larger cost of operation due to the waste water that drains through.