Empty and rinse the tank weekly to prevent mold and bacteria

The reservoir (or collection tank) in your dehumidifier holds water pulled from the air. If you leave that water sitting for more than a few days, mold and bacteria grow inside the tank and can spread back into your home when the unit runs again. The fastest way to stop this is to empty the tank at least once a week, rinse it with clean water, and let it dry before putting it back.

How often you need to empty depends on humidity in your home and the tank size. In a very humid basement, a 50-pint dehumidifier might fill in two or three days. In a drier space, it might take a week. Most people find a weekly schedule works as a practical middle ground — it takes five minutes and keeps the tank from becoming a breeding ground.

Key Takeaways

  • Empty the tank at least once a week, even if it is not completely full, because standing water grows mold and bacteria within days.
  • Rinse the inside with plain water and let it air-dry completely before reinstalling to prevent mold from returning.
  • For stubborn buildup, soak the tank in a 1:1 mix of white vinegar and water for 30 minutes, then scrub with a soft brush.
  • If your dehumidifier has a continuous drain option, connect a hose to bypass the tank entirely and avoid manual emptying.
  • Replace the tank if cracks develop or if mold returns after cleaning, as damaged tanks cannot be fully sanitized.

Step-by-step tank emptying and rinsing

Unplug the dehumidifier before you touch the tank. Slide or lift the reservoir out of the unit — the exact motion depends on your model, but most tanks either slide toward you or lift straight up. Check your manual if you are unsure.

Pour the water down a sink or drain. Do not save it or use it for plants; it contains dust and particles pulled from your air. Once the tank is empty, rinse the inside under running water. Use your hand or a soft cloth to wipe the walls and bottom. Pay attention to corners and seams where mold likes to hide. Rinse again until the water runs clear.

Shake out excess water and stand the tank upright on a clean towel or rack to air-dry completely. Do not reinstall it while wet — moisture left inside creates the same mold problem you just cleaned. Once it is dry (usually 30 minutes to an hour), slide or lift it back into the dehumidifier and plug the unit back in.

Cleaning stubborn mold and mineral buildup

If you see black or green spots inside the tank, or if the water smells musty even after rinsing, the tank needs a deeper clean. Fill the tank halfway with white vinegar and halfway with water. Let it soak for 30 minutes. The vinegar kills mold spores and dissolves mineral deposits left by hard water.

After soaking, use a soft-bristled brush or an old toothbrush to scrub the spots and the seams. Rinse thoroughly under running water several times until you cannot smell vinegar anymore. Dry completely before reinstalling.

If mold returns within a week of cleaning, the tank may have microscopic damage or cracks that trap moisture. In that case, replacement is more practical than repeated cleaning. Tanks are inexpensive (usually $20 to $50) and are available from the dehumidifier manufacturer or online retailers.

Using continuous drain to skip manual emptying

Many dehumidifiers have a drain port on the back or bottom of the unit. If yours does, you can attach a standard garden hose or a condensate pump hose to send water directly to a floor drain, sump pump, or outside. This eliminates the need to empty the tank by hand.

Check your manual for the drain port location and whether your model requires a pump (usually needed if the drain is higher than the exit point). A basic setup takes 10 minutes: attach the hose, run it to your drain, and turn on the unit. The water flows continuously as the dehumidifier runs, so the tank never fills.

The trade-off is that you lose the ability to see how much water the unit is removing, which can be useful for knowing whether your humidity problem is improving. But if you have a finished basement or a space where you cannot easily access the tank, continuous drain saves time and prevents the mold risk that comes with forgetting to empty the tank.

Why tank cleanliness matters for air quality

A dirty dehumidifier tank does not just sit there — it actively releases mold spores and bacteria back into the air when the unit runs. The fan pulls air through the tank area, and if mold is growing there, you are spreading it through your home. This is especially a problem for people with asthma or mold allergies.

Weekly emptying and rinsing takes less time than dealing with respiratory problems or having to replace the dehumidifier because mold has colonized the internal components. The tank is the easiest part of the unit to access and clean, so keeping it dry and mold-free is the single most important maintenance step you can do.

Signs your tank needs replacement

Cracks or splits in the plastic mean water can leak inside the dehumidifier body, damaging the motor and electronics. If you see cracks, stop using the unit and order a replacement tank before running it again.

Discoloration that does not come off with vinegar soaking, a persistent smell even after cleaning, or mold that returns within days of a thorough cleaning all suggest the tank has absorbed mold into the plastic itself. Once that happens, cleaning only works temporarily. Replacement is the practical choice.

Most tanks are model-specific, so order by your dehumidifier's model number (usually on a sticker on the back or inside the manual). Installation is the reverse of removal — slide or lift the new tank into place and plug in the unit.

Frequently Asked Questions

Can I use bleach to clean the dehumidifier tank?

Bleach works but vinegar is safer and just as effective. Bleach fumes can linger in the plastic and get pulled into your air when the unit runs. White vinegar kills mold spores, dissolves mineral deposits, and leaves no harmful residue. Rinse thoroughly either way before reinstalling.

What if I forget to empty the tank and it overflows?

Most dehumidifiers have a float switch that shuts off the unit when the tank is full, so overflow is rare. If water does leak out, unplug the unit, empty and clean the tank, and check the floor around the dehumidifier for water damage. Mold can start growing on carpet or wood within 24 to 48 hours, so dry the area quickly with fans or a wet-dry vacuum.

Is it normal for the tank to smell bad?

A slight musty smell is normal if the tank sits for a few days, but a strong odor means mold is growing. Empty and rinse the tank when ready, then soak it in vinegar and water. If the smell returns after cleaning, replace the tank.

Can I leave the dehumidifier running while the tank is out?

No. Without the tank in place, water has nowhere to go and can damage the internal components or leak onto your floor. Always unplug the unit before removing the tank, and plug it back in only after the tank is reinstalled and dry.

How long does it take for mold to grow in a full tank?

Mold can begin growing within 24 to 48 hours in a warm, humid environment. This is why weekly emptying is important — you do not have to wait until the tank is full or until you see visible mold. Regular emptying prevents the problem from starting.