Empty and rinse the tank weekly to prevent mold and bacteria

A dehumidifier tank collects water pulled from the air in your home. That standing water becomes a breeding ground for mold, algae, and bacteria within days if you don't clean it. The tank needs to be emptied and rinsed at least once a week, more often if you live in a very humid climate or run the unit constantly.

The good news: cleaning takes about five minutes and requires only water and a soft brush or cloth. You don't need special chemicals or tools. A clean tank keeps the water fresh, prevents odors from spreading back into your room, and helps the dehumidifier work at full strength.

Key Takeaways

  • Empty the tank at least once a week, or whenever it reaches the full line, to stop mold and bacteria from growing in standing water.
  • Unplug the dehumidifier before you remove the tank, and let any remaining water drain completely into a sink or bucket.
  • Scrub the inside bottom and sides with a soft brush or cloth and plain water, paying special attention to corners where algae tends to collect.
  • Dry the tank completely with a clean cloth before putting it back in the unit to prevent mold from returning when ready.
  • If you see black or green spots that won't scrub away, soak the tank in a mixture of one part white vinegar to three parts water for 30 minutes.

Step 1: Unplug the unit and locate the tank

Always unplug the dehumidifier before you touch the tank. This is a safety step — you are working with water and electricity, and unplugging removes that risk entirely. Most dehumidifiers have the tank mounted on the front or back of the unit, held in place by a straightforward latch or clip.

Check your manual if you are unsure where the tank is or how it releases. Some models slide straight out; others twist or require you to press a button on both sides. The tank is usually made of clear or translucent plastic so you can see the water level from outside the unit.

Step 2: Drain the water completely

Once you remove the tank, take it to a sink or bathtub and pour the water down the drain. Tilt the tank slowly so the water flows out evenly and doesn't splash. If the tank is heavy or awkward to carry, place a bucket underneath it first, then carry both to the sink together.

Let the tank sit for a moment after you pour to make sure all the water has drained from the corners and edges. Any water left inside will mix with cleaning water and make the job harder. If your tank has a drain plug at the bottom (some models do), you can open that instead of pouring — check your manual to see if yours has one.

Step 3: Scrub the inside with a soft brush and water

Fill the empty tank halfway with lukewarm tap water. Use a soft-bristled brush, a sponge, or a clean cloth to scrub the inside bottom and all four sides. Pay close attention to the corners and seams — algae and mold love to hide in those spots and are harder to see on clear plastic.

Scrub in circular motions and don't press hard; you are not trying to sand the plastic, just loosen the buildup. Drain this dirty water and repeat with fresh water one more time to rinse away any loose particles or soap residue. The water should run clear when you pour it out.

Step 4: Deal with stubborn mold or algae spots

If you see black, green, or brown spots that won't come off with plain water and scrubbing, the tank has developed mold or algae. These spots are harmless to touch but mean the tank needs a stronger clean. Mix one part white vinegar with three parts water in the tank, filling it about halfway.

Let the tank soak in this mixture for 30 minutes. The vinegar kills mold and algae without damaging the plastic. After soaking, scrub again with your soft brush, then drain and rinse twice with fresh water. If spots remain after a second vinegar soak, the plastic may be permanently stained, but the tank is still clean and safe to use.

Step 5: Dry the tank and reinstall it

Use a clean, dry cloth to wipe down the inside and outside of the tank. Pay special attention to the bottom and corners — any standing water left behind will grow mold again within hours. You can also stand the tank upside down in a dish rack for 10 minutes to let gravity finish the job, then wipe it dry.

Once the tank is completely dry, slide or clip it back into the dehumidifier. Make sure it sits flush and the latch or clip is fully engaged so it does not fall out during operation. Plug the unit back in and you are done. Set a reminder on your phone to clean the tank again in one week.

Common mistakes that lead to mold returning

The most common mistake is putting a damp tank back into the unit. Even a little moisture left inside will grow mold within 24 hours because the tank sits in a dark, humid environment. Always dry it completely with a cloth before reinstalling.

The second mistake is skipping the weekly clean and waiting until the tank is full. By then, the water has been sitting for days and the tank walls are already coated with algae. Cleaning becomes harder, and odors have already started to develop. Empty and rinse the tank on the same day each week — Sunday morning works well for many people — so it becomes a habit.

A third mistake is using hot water or harsh chemicals. Hot water can warp some plastic tanks, and bleach or strong cleaners are not necessary and can leave residue that gets into the air when the unit runs. Plain water and a soft brush are all you need for routine cleaning. White vinegar is the only additive you should use, and only when mold or algae appears.

Frequently Asked Questions

How often should I clean the tank if I run the dehumidifier all day?

If the unit is running constantly or in a very humid space, the tank may fill and need emptying every two to three days. Empty it whenever it reaches the full line, and rinse it each time you empty it. In less humid conditions, once a week is usually enough.

Can I use bleach to kill mold in the tank?

Bleach is not recommended. It can damage some plastic tanks over time and leaves a chemical smell that the dehumidifier will blow back into your room. White vinegar works just as well and is safer for the plastic and your air quality.

What if water is leaking from the tank?

Check that the tank is sitting flush in its slot and the latch is fully engaged. If water still leaks, the tank may have a crack. Look for visible damage on the bottom or sides. A cracked tank needs to be replaced — you can order a replacement from the manufacturer using your dehumidifier's model number.

Is it normal for the tank to smell bad?

A slight musty smell is normal if the tank has not been cleaned in a while, but a strong odor means mold or bacteria is growing. Clean the tank when ready with vinegar and water, and then clean it weekly to prevent the smell from returning.

Can I leave the tank out and let the dehumidifier drain into a bucket instead?

Some dehumidifiers have a drain hose option, but most do not. Check your manual to see if yours supports continuous drainage. If it does, you can run a hose to a floor drain or bucket, which saves you from emptying the tank by hand. The tank still needs to be cleaned monthly even if you use a drain hose.