How to Clean a Top-Loading Washing Machine (and Why It Matters for Your Clothes)

By Kristina Braly, MD — Founder, AEMBR

Your washing machine's job is to clean things. It stands to reason, then, that the machine itself stays clean. But if you've ever pulled out a load of laundry that smells faintly off, noticed dark specks on the drum rim, or felt an inexplicable film on your freshly washed towels, you already know: washing machines get dirty. And a dirty washing machine does not clean your clothes.

As a physician who has spent years formulating laundry products, I think about this problem differently than most. It's not just about aesthetics. It's about biofilm, residue accumulation, and what those things are actually doing to your fabrics—and potentially to your skin. This is the guide I wish existed when I started asking these questions myself.

Why Washing Machines Get Dirty

Every wash cycle introduces two things into your machine: soils from your clothes (body oils, sweat, skin cells, food residue) and chemistry from your detergent (surfactants, enzymes, fragrance, fillers). In a well-functioning cycle, both rinse away cleanly. In reality, residue accumulates.

Several factors accelerate this:

• Low-temperature washing: Cold and warm cycles are gentler on fabrics and energy bills, but they don't kill bacteria or fully dissolve waxy soils.
• High-sudsing detergents: Conventional liquid detergents produce more foam than a high-efficiency machine can fully rinse. That foam leaves a film on the drum, agitator, and hoses.
• Leaving wet laundry in the drum: Even a few hours of damp warmth inside a closed machine is ideal for mold and mildew to establish.
• Hard water: Mineral deposits from calcium and magnesium build up on heating elements, drum walls, and seals over time.

The result is a biofilm—a structured community of bacteria and mold adhered to surfaces inside your machine. Once biofilm is established, it's resilient. Routine wash cycles don't disrupt it. And it's what's responsible for that persistent musty smell that some people describe as the laundry room "always smelling a little off."

What Biofilm Actually Does to Your Clothes

This is where it matters medically. Biofilm in your washing machine can:

• Re-contaminate fabrics during wash cycles—particularly absorbent items like towels and sheets
• Produce volatile compounds responsible for that sour, mildew odor on clothes that smelled fine going in
• Trigger contact dermatitis flares in people with sensitive skin or fragrance sensitivities, particularly infants
• Reduce the effective cleaning power of your detergent, because enzymes and surfactants have to work against residue in addition to soil

None of this is theoretical. Studies published in journals including Applied and Environmental Microbiology have identified Pseudomonas, Acinetobacter, and various mold species in consumer washing machines—particularly those used primarily at low temperatures. The issue is most acute in households with infants, elderly family members, or anyone immunocompromised.

How Often Should You Clean a Top-Loading Washing Machine?

General guidance:

• Monthly if you wash primarily in cold water or have a household with heavy laundry load (kids, pets, athletic clothing)
• Every 6–8 weeks as a baseline for moderate household use
• Immediately if you notice musty odor, visible residue on the drum rim or agitator, or clothes coming out with an off smell

Top-loaders generally accumulate residue faster than front-loaders in the drum and agitator but are easier to clean because the door and gasket aren't issues. The flip side: top-loaders often have more interior surface area—agitator fins, the underside of the lid, the fabric softener dispenser—that collects residue and gets overlooked.

What You'll Need

Ingredient	Purpose	Notes
White vinegar (distilled, 5% acidity)	Dissolves mineral deposits; loosens detergent residue	Use distilled white, not apple cider
Baking soda	Mild abrasive; neutralizes odors	Standard grocery store variety
Microfiber cloth or old toothbrush	Manual scrubbing of dispenser, agitator, lid	Essential for crevices
Hot water setting	Disrupts biofilm; dissolves residue	Use the hottest setting your machine offers
Oxygen boost (optional)	Enzyme-assisted oxidation for stubborn biofilm	AEMBR Oxygen Boost — no chlorine bleach required

A note on commercial washing machine cleaners like Affresh: they work, and I have no objection to them. The active ingredient is essentially sodium percarbonate—which is also the active in most oxygen boost products. You can get the same function from a clean oxygen boost without the single-use plastic tablet packaging.

Step-by-Step: How to Clean a Top-Loading Washing Machine

This method works with or without an agitator. If your machine has a dedicated "clean cycle" setting, use it—it runs hotter and longer than a standard wash cycle.

Step 1: Wipe down the interior surfaces first.
Before you run any cleaning cycle, take a microfiber cloth dampened with white vinegar and wipe down the inside of the drum, paying attention to the top rim, the underside of the lid, any dispensers (fabric softener and detergent), and the top of the agitator. These areas accumulate residue and mold that a cleaning cycle alone won't fully address.

Step 2: Run a hot water cycle with vinegar.
Set your machine to the largest load size and hottest temperature. As the drum fills, add 4 cups of distilled white vinegar. Let the cycle agitate for about 1 minute, then pause the machine and let it soak for 30–60 minutes. This gives the acetic acid time to work on mineral deposits and break up residue.

Step 3: Complete the vinegar cycle.
Let the cycle finish and drain completely.

Step 4: Run a hot water cycle with baking soda.
Start another hot cycle at the largest load size. Add 1 cup of baking soda as the drum fills. Let this cycle run to completion without pausing. The baking soda neutralizes any remaining vinegar residue, deodorizes the drum, and provides mild abrasion through agitation.

Step 5: Clean the dispenser drawers and agitator manually.
Remove any removable components—fabric softener dispensers, detergent drawers—and soak them in a vinegar solution or scrub with an old toothbrush. For fixed dispensers, use a toothbrush with diluted vinegar. The agitator on top-loaders is particularly prone to buildup in the fins and at the base; scrub thoroughly.

Step 6: Wipe dry and leave the lid open.
After the cleaning cycles, wipe the drum dry with a clean cloth and leave the lid open for several hours. This is the single most important preventive step you can take. A closed lid traps warmth and moisture—exactly what mold and mildew need to establish.

When to Use an Oxygen Boost Instead of Bleach

Some cleaning guides recommend chlorine bleach for washing machine cleaning. Bleach is genuinely effective at killing bacteria and mold—but it comes with trade-offs. Chlorine bleach degrades rubber seals and hoses over time. It can react with other cleaning residue in the machine to produce chlorinated compounds. And many households are appropriately cautious about chlorine bleach around children and pets.

Oxygen boost (sodium percarbonate, which releases hydrogen peroxide on contact with water) provides oxidative cleaning power without these concerns. It's color-safe, degrades to water and oxygen, and is effective against biofilm and organic residue. I use it as the primary booster in heavy-duty cleaning cycles.

For a seriously neglected machine—visible mold, strong persistent odor—substitute ½ cup of AEMBR Oxygen Boost in Step 2 instead of or alongside the vinegar. Let it soak for a full hour before completing the cycle.

The Detergent Connection: Why Your Detergent Affects Machine Cleanliness

This is worth addressing directly: the single most influential factor in how fast your washing machine accumulates residue is the detergent you use.

Conventional liquid detergents are formulated to be highly stable and to produce visible suds—which consumers read as "working." But that stability comes at a cost: liquid detergents often contain hydrotropes, thickeners, and preservatives that don't fully rinse in a single cycle. They accumulate in the drum, in hoses, and in dispensers. High-sudsing formulas are particularly problematic in HE machines that use less water.

Powder detergents, particularly those formulated without fillers and phosphates, rinse more cleanly than most liquids. They don't require preservatives to extend shelf life, and their surfactant systems tend to be simpler. This is part of why I formulated AEMBR Laundry Powder in powder form: it doses precisely, produces no excess foam, and leaves no liquid residue in dispensers or drums.

If you've been using a high-sudsing liquid detergent and your machine smells, cleaning it thoroughly and then switching to a clean powder formula will compound the benefit significantly.

Preventive Habits That Actually Work

The most effective washing machine maintenance isn't the monthly deep clean—it's the daily habits that prevent buildup from establishing in the first place.

• Leave the lid open after every load. Non-negotiable. Airflow prevents moisture from accumulating. This alone dramatically reduces mold and mildew formation.
• Transfer wet clothes promptly. Clothes sitting wet in a drum for more than 30–60 minutes begin to develop odor. The machine absorbs that, too.
• Use the correct detergent dose. More detergent does not mean cleaner clothes. It means more residue. Follow the package instructions, and if you have soft water, use the lower end of the range.
• Run an occasional hot cycle—even on a cold-wash household. A monthly hot wash (even with just a small load of whites or towels) helps prevent biofilm from establishing in the drum and hoses.
• Don't use fabric softener regularly. Liquid fabric softener is one of the fastest ways to build residue in a top-loader—particularly in the softener dispenser. Wool dryer balls achieve the same softening effect without leaving a coating on your machine.

Signs Your Machine Needs Immediate Cleaning

• Clothes smell musty or sour immediately after washing
• Visible dark spots or film on the drum, agitator, or lid rim
• Fabric softener dispenser has a sticky, filmy residue
• The machine itself has a persistent musty or chemical odor even when empty
• White towels are developing a grayish tint over time
• New clothes are coming out with an odor they didn't have going in

If you're seeing several of these signs, do a full cleaning cycle with an oxygen boost soak before switching detergents or assuming the problem is with your clothes.

What About Front-Loaders?

Front-loading machines have their own unique cleaning requirements centered on the door gasket—that rubber seal that traps moisture, hair, and residue after every cycle and is the primary site of mold growth in front-loaders. The cleaning method is similar in principle (hot cycle + oxygen boost or vinegar) but requires manual gasket cleaning with every use, not just monthly. If you've switched from a front-loader to a top-loader partly because of the smell problem, you're not imagining it: top-loaders are genuinely easier to keep clean because there's no gasket to maintain.

A Note on Machine Warranty and Commercial Cleaners

Many washing machine manufacturers now include a "drum clean" or "tub clean" cycle specifically for this purpose—check your manual. These cycles run hotter and longer than standard cycles. Some manufacturers (including Samsung and LG) recommend using their branded cleaner tablets in this cycle; others explicitly allow any washing machine cleaner or even plain hot water.

White vinegar is safe for use in virtually all top-loading machines. The acetic acid concentration in 5% distilled white vinegar is not high enough to damage rubber seals or metal components with normal cleaning frequency (monthly or less). If you're concerned, run a plain hot rinse cycle after the vinegar cycle to clear any residue before the baking soda step.

The Bottom Line

A clean washing machine is a prerequisite for genuinely clean laundry. It's not a nice-to-have maintenance task; it's the foundation that makes everything else—detergent choice, wash temperature, cycle selection—work as intended. A monthly cleaning cycle, daily ventilation habits, and a residue-minimal detergent formula will keep most machines performing well for years without the musty smell that many households accept as normal. It's not normal. It's preventable.

Start with the habits. The machine will take care of itself from there.

---

Quick Reference Checklist

• ✅ Monthly: Hot cycle with 4 cups white vinegar (soak 30–60 min) → drain → hot cycle with 1 cup baking soda
• ✅ Monthly: Scrub agitator fins, dispenser drawers, lid rim with toothbrush + diluted vinegar
• ✅ Heavy buildup: Add ½ cup AEMBR Oxygen Boost to soak cycle instead of or alongside vinegar
• ✅ Daily: Leave lid open after every load
• ✅ Daily: Transfer wet clothes promptly (within 30–60 min)
• ✅ Ongoing: Use a residue-minimal powder detergent; correct dose
• ✅ Ongoing: Run one hot cycle per month (even if you wash mostly cold)
• ✅ Skip: Liquid fabric softener in the machine — use wool dryer balls instead

For a complete non-toxic laundry routine, explore AEMBR Laundry Powder — formulated without fillers, phosphates, or synthetic optical brighteners, and designed to rinse clean in every machine type.