Ultrasonic Mist Maker Build & Setup Guide

To make a DIY humidifier, simply place an ultrasonic mist maker in a water reservoir, then use a small waterproof fan to push air into your water reservoir and the mist through output holes into your grow tent, room, or enclosure. You can create a fully automated humidifier by connecting a humidistat for automated humidity control and adding an auto-fill water valve. For step-by-step instructions, including recommended parts and assembly instructions, see our blog post on How to Build a DIY Humidifier.

You don’t need to adjust output just to make mist—your mist maker will run at full output by default. However, there are several safe ways to reduce or control mist output, depending on your specific needs:

• First: Never remove a disc to reduce output. Removing discs will damage your mist maker and void warranties. Never allow water under the discs.
• Precise, Automated Control: For applications requiring accurate humidity—such as mushroom cultivation, laboratory humidification, meat or cheese curing, incubators or home humidification—use our humidistat controller. This device automatically cycles your mist maker on and off to maintain your desired humidity level at the preset levels.
• Manual Output Adjustment: For easy, hands-on control—ideal for special effects, cooling, or flexible environments—our Mist Output Controller lets you turn down the mist output with a simple voltage control dial.

A float is strongly recommended, but a mist maker can run without one as long as the water level and the mist maker’s position remain perfectly stable. You must maintain at least 20 mm (about 0.8 inches) of water above the surface of the ceramic disc at all times; too much or too little water will cause performance issues or stop mist production altogether. The supplied float automatically keeps your mist maker floating at the ideal depth for consistent operation and maximum mist output.

The 120mm fan is our most popular choice and works well for most applications larger than 2x4 feet that also need sufficient fresh air exchange (grow tents). Use it for maximum mist dispersion in grow tents, greenhouses, rooms, or other similar spaces.

For smaller setups like terrariums or special effects, an 80mm fan is often sufficient. It provides enough airflow without overwhelming the space, or diluting the fog with air. This will give a foggy flow for a cool creeping fog effect.

Additionally, with larger mist makers, you can turn down the speed on a 120mm fan to achieve a similar slow-effect mist if desired. This is ideal for large mist makers when making a water-only fog machine.

• Do NOT add bleach to your reservoir, as it WILL immediately damage the mist maker discs. It also chemically reacts with the stainless steel and will cause corrosion.
• The easiest method to keep water clean is to use our UV sterilizing light. Just drop it into the reservoir to kill bacteria and algae, greatly extending the time between cleanings and assuring the mist output is clean.
• You can also add 3% hydrogen peroxide at a 20:1 water-to-peroxide ratio once per week. Adjust the dosage based on effectiveness in your environment. You can also find stronger concentrations online.
• Always avoid mist makers with LEDs and clear reservoirs. The light in your reservoir will cause algae and promote bacterial growth.

Regular sterilization with these safe methods ensures optimal mist output and extends the life of your ultrasonic mist maker.

Most of the time, yes—the fan should be plugged into the humidistat. This setup allows the humidistat to automatically turn the fan on at the same time as the mist maker. Most humidistats, like our Willhi Humidistat, have one plug. Some have two, like our Inkbird Humidistat. However, on the Inkbird, one is for humidification and one is for dehumidification. With both humidistats, you will need a plug splitter or power strip to plug both the fan and mist maker into the humidistat.

If your application requires fresh air exchange in the humidified area, you can run the fan constantly to maintain airflow independently of the humidistat's control and feed fresh air into your room using the fan. Then, when the mist maker turns on, it will humidify the incoming air.

The most likely cause is that your fog output holes are too small. When the fog tries to escape the water reservoir, if the holes are restrictive, the pressure can push fog back up through the fan rather than flowing smoothly out the exhaust holes. A 4" output hole is recommended. Smaller holes will result in lower fog transfer and reduce efficiency.

To fix this issue:

• Increase the size of the output holes to allow the fog to escape freely, preventing it from being forced back through the fan blades.
• If your output holes cannot be adjusted, try reducing the fan speed. A slower fan speed moves less air, helping the fog flow properly without pushing back.