Causes
- The water tank is not fully seated, so its outlet valve never opens — the 516S reads water level through the tank's outlet valve on the base. If the 1.3 L tank is resting slightly high, tilted, or not pressed down far enough, the valve stays closed, no water flows into the atomizing chamber, and the unit reports low water and stops misting even though the tank is full. This is the most reported false-low-water scenario across DREO's TurboCool misting fans.
- An air lock or bubble in the water path after refilling — after you lift the tank out and refill it, air can be trapped in the feed line between the tank valve and the ultrasonic chamber. The sensor sees an empty chamber and triggers the low-water shutdown even with a full tank, until the water works its way through.
- Scale or debris confusing the water-level sensor — hard-water mineral deposits (the same white dust that collects in the tank) can build up on the water-level sensor in the base, making it misread a full chamber as empty. Detergent residue from an aggressive cleaning can do the same thing.
- The unit is not sitting flat — the 516S water sensor relies on a level base. On a tilted or uneven surface the water in the shallow atomizing chamber shifts away from the sensor, producing a false low-water reading. DREO's troubleshooting explicitly lists placing the appliance on a flat, level surface.
- A defective water-level sensor or tank valve — some TurboCool units shipped with a faulty sensor or a sticking tank valve. One owner of the near-identical TurboCool 765S reported the mister stopping with a false low-water warning the day after purchase; DREO support confirmed the defect and replaced the unit.
How to Fix
- Reseat the water tank firmly — lift the tank straight off, wipe the outlet valve on the bottom, then press it back down until it seats flush against the base with no gap. You should feel it drop into place and hear water begin flowing into the base. If the tank was riding on a towel, cable, or debris, that alone can trigger the warning.
- Clear the air lock by priming the water path — with the tank seated, pour a small splash of clean water directly into the base's atomizing chamber (about 50-100 mL), then turn the mist level to 3 for a couple of minutes. The extra water bridges the gap while the feed line fills, and the unit usually starts misting normally once flow is established.
- Check that the tank is actually full and the valve is open — remove the tank and confirm the water level; the 516S's transparent tank makes this easy. Inspect the outlet valve on the bottom of the tank: it should push in and spring back. If it's stuck, rinse it under warm water. Remember the unit stops misting automatically at genuinely low water — if the tank is below about a quarter full, just refill it.
- Clean the water-level sensor and descale the base — empty the base and wipe the sensor area with a soft cloth and a little white vinegar or citric-acid solution, then rinse thoroughly with clean water. If you used detergent during cleaning, rinse several times so no residue remains on the sensor. Switch to purified or distilled water to slow future scale buildup.
- Place the unit on a flat, level surface — move the 516S to a hard, level desk or tabletop. If the base is tilted, water shifts away from the sensor and the low-water warning returns even after a clean reseat. Confirm the unit doesn't rock before powering it back on.
- Power-cycle the fan and retry — unplug the 516S for 30-60 seconds, plug it back in, reseat the tank, and run mist at level 3. This resets the water-sensing logic. Also check the DREO app for a pending firmware update, since DREO has shipped water-detection improvements to the TurboCool line since launch.
- Contact DREO support if the warning persists — if the tank is full and seated, the base is level and clean, and the unit still reports low water, the sensor or tank valve is likely defective. Contact DREO support at support.dreo.com with your order number — TurboCool owners with a confirmed sensor fault received a replacement unit under warranty.