Maintaining Water Levels Without Electronics: A Low-Flow Passive Solution

Hello. Here is a bit of backstory: we recently received a new medium-temperature cold room to be used as a proofing chamber. To regulate humidity, a fog generator was installed—though it turned out to be a fairly flimsy setup, much like the company that provided it. The real issue, however, was that the installers failed to set up a water level maintenance system for the container where the ultrasonic fog generator (Mist Maker) floats.

Since this device requires distilled water, a standard solenoid valve connected to a tap was out of the question. We decided to weld a custom stainless steel tank to maintain the level passively. While we had the storage figured out, we didn’t want to use expensive specialized valves or electronic level sensors for such a simple task. That’s when I recalled a classic design often seen on farms for watering poultry.

The principle behind this waterer is straightforward: as long as the water level in the bottom tray remains above the lower edge of the reservoir (the jar), air cannot enter the container. This creates a vacuum (or more accurately, the internal pressure remains lower than the external atmospheric pressure), preventing water from flowing out. As soon as the water level drops below the edge of the tube, air bubbles enter the reservoir, and water is released until the level rises and seals the tube again.

While this isn’t the most precise dosing method, it was perfect for our needs. We implemented the following scheme:

Legend:

1. Tank containing distilled water for dosing.
2. 2″ ball valve.
3. 1/2″ ball valve.
4. Filler neck.
5. Working tube.
6. The container where the level needs to be maintained.

If your installation experiences vibration, you can “break” the working tube and connect the two parts with a flexible hose. I did this to make maintaining the fog generator easier.

To fill the tank:

1. Close the lower valve.
2. Open the upper valve and pour in the water.
3. Switch the valves in reverse order (close the top, then open the bottom).

Important: Make sure to post clear instructions next to the tank. If someone opens the upper valve without closing the lower one first, all the water in the tank will immediately dump onto the floor.

The exact height at which the water is replenished depends on the dimensions of your tank and the diameter of the working tube. In my setup, the level fluctuates by about 30mm.

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Thanks for reading! 🙂