That musty, sour smell coming from your washing machine is one of those household problems that can make you want to hold your breath every time you open the lid. The good news is that a smelly washer is almost always fixable with a few simple habits and a little elbow grease. You do not need a repair person for most odor problems, and you definitely do not need to replace the machine.

The first thing to understand is that washing machines are damp, dark places. That combination is perfect for mold and mildew. Even though the machine fills with water and soap, it does not stay clean on its own. Soap scum, lint, body oils, and leftover detergent can collect in hidden areas. Over time, those deposits feed bacteria and mold, and that is what you smell.

Front-loading washers are famous for this problem, but top-loaders can get smelly too. On a front-loader, the rubber door gasket is the usual suspect. That folded seal traps water, lint, and small items like socks or hair ties. If you pull back the edge of the gasket and see dark specks or feel slimy residue, you have found a major source of the odor. Wipe that area with a mixture of equal parts water and white vinegar, then dry it completely. Do this once a month to keep mold from coming back.

The detergent drawer is another hiding spot. Many people pour in liquid detergent and fabric softener and never think about the residue that builds up behind the drawer. Pull the drawer out completely if your machine allows it, and rinse it in warm water. Use an old toothbrush to scrub the corners and the little siphon cap. While the drawer is out, look inside the slot where it slides in. You may see black gunk or hardened powder. Wipe that area clean with vinegar and a rag.

The drain filter is easy to forget. On many front-loaders, there is a small door near the bottom of the machine that hides a filter. Place a towel and a shallow pan underneath before you open it, because water will come out. Unscrew the filter, remove any coins, hair, or lint, and rinse it clean. If your machine has a self-cleaning filter, you may not need to do this, but check your manual to be sure.

Detergent residue is a sneaky cause of smells. Using too much detergent, especially cold water and the wrong type of detergent, leaves a film inside the drum and hoses. That film attracts dirt and holds odor. Try using less detergent than the bottle suggests. For high-efficiency machines, always use HE detergent. Once a month, run an empty hot water cycle with two cups of white vinegar in the drum. Some people add half a cup of baking soda to the drum as well. Do not mix vinegar and baking soda in the same cup because they will fizz and cancel each other out. Add them separately. If you prefer a store-bought washing machine cleaner, follow the package directions, but vinegar works just as well for most routine cleanings.

After every wash, leave the door or lid open so the inside can dry. This one habit makes a huge difference. Wipe down the door gasket after each use if you have a front-loader. Remove wet laundry promptly. Do not let clothes sit in the drum for hours after the cycle ends. Also, check the drain hose for kinks or clogs. If the machine cannot drain fully, standing water will sour quickly. Also, make sure the machine is level and not rocking, because poor balance can cause water to pool in odd places. A dry drum is a happy drum.

If you have tried all of these steps and the smell persists, the problem may be in the drain pump or the internal hoses. That is when you should call a technician. But for most homeowners, a monthly cleaning routine and a little attention to the gasket, drawer, and filter will keep the washer smelling fresh. Your clothes will smell better, your machine will last longer, and you will not have to hold your breath every time you open the lid.