Why Washing Machines Start To Smell

A washing machine that smells is not dirty in the way a floor is dirty. A living layer has established itself inside the parts that never dry, and it feeds on what the wash leaves behind.

The residue that accumulates

Every wash deposits a small amount of undissolved detergent, fabric softener, body oils and fibre in the parts of the machine outside the drum.

Over hundreds of cycles this forms a soft, greasy film on the outer tub, the door seal and the pipework, which is where the odour actually originates.

Because the film is out of sight, the machine appears clean while the smell continues, and cleaning the visible drum has almost no effect on it.

Cool washing is the main driver

Modern detergents are formulated to work at low temperatures, which saves energy and is gentler on fabric. It also never gets hot enough to disrupt the film.

A machine used exclusively at low temperatures therefore accumulates residue steadily with nothing to interrupt it, which is why the problem has become more common over the last decade.

An occasional hot cycle with no load resets this. The heat and the detergent together break down the deposit that low washes leave behind.

Detergent type and quantity matter

Powder detergents generally contain bleaching agents that suppress growth, while liquids and capsules usually do not, which is why liquid-only households see the problem sooner.

Overdosing makes it worse rather than better. Excess detergent does not rinse away fully and becomes part of the residue that feeds the film.

Fabric softener is a particular contributor, being an oily conditioner designed to deposit on fibres. Anything designed to deposit will also deposit inside the machine.

The places to check

The door seal on a front loader has a fold that holds water permanently and traps fibre, coins and hair. It is the most common single source and the easiest to clean.

The detergent drawer and its housing accumulate a thick sludge behind the visible compartments, and most drawers pull fully out for washing.

The filter at the base catches everything that came off the laundry. If it has not been opened in a year, its contents will explain a great deal.

Keeping it from returning

Leaving the door and the drawer open between washes allows the interior to dry, which removes the moisture the film depends on.

Removing laundry promptly matters for the same reason, since a wet load left in a closed drum reintroduces the smell into the clothes themselves.

Where a smell persists after all of this, the deposit may be in the sump or the drain hose, and that is the point at which an engineer is a better use of time than another cleaning cycle.