Mold in the washing machine, toilet or dishwasher

Why it happens in these places

Mold needs moisture and something to feed on. Appliances that use water give it both: constant damp, warmth, and a film of detergent, fabric softener, food or body oils. Rubber seals, hidden drawers and drain areas never fully dry.

Not everything dark or slimy is mold. Pink or orange film is usually bacteria. Black slime in a drain is often a mix of bacteria and mold growing on soap residue. For cleaning purposes the distinction matters little: remove it, and let things dry.

Front-loading washing machines

The commonest complaint. Black spots on the grey door seal and a sour smell in the drum and on clean laundry.

Why: the door seals tight, so the drum and the folds of the rubber gasket stay wet. Low-temperature washes and too much detergent or softener leave a film.

Cleaning

1. Pull back the folds of the door seal and wipe out lint, hair and slime with a cloth and detergent solution. An old toothbrush reaches the groove.
2. Remove the detergent drawer, wash it in hot soapy water and clean the cavity it slides into.
3. Clean the drain pump filter, usually behind a small panel at the bottom front. Have a towel and a shallow tray ready.
4. Run the machine’s cleaning cycle, or the hottest cycle, empty, with a washing machine cleaner or the product the manufacturer recommends.
5. Wipe the door glass and dry the seal.

Follow your machine’s manual. Some manufacturers advise against certain cleaners.

Preventing it

• Leave the door and the detergent drawer ajar after each wash
• Wipe the seal dry
• Use the correct amount of high-efficiency detergent. More is not better.
• Go easy on liquid fabric softener
• Run a hot wash regularly
• Take laundry out promptly
• Run a cleaning cycle monthly

A seal that is deeply stained or perished can be replaced.

Top-loading washing machines

Growth collects under the rim of the tub, in the softener dispenser and beneath the agitator. Clean the rim and dispensers with a brush, run a hot cleaning cycle and leave the lid open between washes.

Toilets

In the bowl: a dark ring at the waterline, or black spots under the rim. The ring is usually a combination of mineral scale, which gives growth a rough surface to hold onto, and bacteria or mold. Toilets that are seldom flushed are worst.

In the tank: dark slime or spots on the walls. The tank holds standing water in the dark, and sediment or iron in the water feeds bacteria.

Cleaning the bowl

1. Scrub with a toilet brush and toilet cleaner, including under the rim.
2. For a stubborn ring, a pumice cleaning stone made for porcelain removes scale. Keep it wet.
3. Flush.

Cleaning the tank

1. Shut the supply valve and flush to empty the tank.
2. Scrub the walls with a brush and a mild cleaner.
3. Turn the water on, let it fill and flush a couple of times.

Avoid drop-in bleach tablets in the tank. They can damage the rubber flapper and seals, which leads to a running toilet.

Preventing it: flush little-used toilets every few days, clean weekly, and fix a running toilet. Where the water is very hard, descale periodically.

Mold on the outside of the tank or the wall behind it is a different matter. That is condensation on a cold tank in a humid bathroom, and the answer is ventilation.

Dishwashers

Black or pink growth around the door gasket, in the filter, at the bottom of the door and in the corners of the tub.

Cleaning

1. Remove and wash the filter at the bottom of the tub. Many people do not know it is there.
2. Wipe the door gasket and the bottom edge of the door, which the spray does not reach.
3. Clear the spray arm holes.
4. Run the hottest cycle empty with a dishwasher cleaner.

Preventing it: scrape plates, clean the filter every few weeks, leave the door ajar after a cycle so that the tub dries, and run a hot cycle regularly. A dishwasher used rarely is more prone to it.

Fridges

Growth appears on door gaskets, in the drip tray underneath, and around the water dispenser. Wipe gaskets with detergent solution, clean spills promptly, empty and wash the drip tray, and replace the water filter on schedule. Mold on forgotten food spreads spores to other food, so clear it out.

Other damp spots

• Shower heads and tap aerators: unscrew and scrub
• Sink overflows and drains: brush with detergent, then flush with hot water
• Humidifiers: empty daily and clean as the manufacturer directs. A dirty humidifier sprays what is growing in it into the air.
• Dehumidifier buckets: wash regularly
• Air conditioner drip pans: keep the drain clear
• Front-load washer and dishwasher drain hoses: check for kinks that hold water

Is it a health concern?

For most people these are a nuisance and a source of smells. Anyone with asthma, allergies or a weakened immune system may be more affected and should not be the one doing the scrubbing. Wear gloves, ventilate, and never mix bleach with other cleaners.

When it is more than cleaning

Call for help if:

• Mold is growing on the wall, floor or cabinet beside the appliance. That suggests a leak.
• The floor near the washer or dishwasher is soft, swollen or stained
• There is a musty smell that cleaning the appliance does not remove
• Growth keeps appearing on surfaces around the appliance

An appliance that leaks slowly wets the subfloor and wall where you cannot see. See dishwasher leaks and washing machine floods.

More: mold removal and remediation.