Why Does My Siemens Washing Machine Smell Bad?
Run an empty 90°C service wash with a washing machine cleaner tablet or 250ml of white vinegar placed directly in the drum — this kills bacteria and removes residue buildup in most cases (takes about 15 minutes to set up, then let the cycle run).
Fault description
A bad smell coming from your Siemens washing machine is one of the most common complaints homeowners report, and the good news is that it is almost always caused by something you can fix yourself without any tools or spare parts. The odour typically develops gradually and is often described as musty, sour, or similar to mildew — the same smell you might notice on a damp towel left too long before drying.
The root cause is nearly always biological: bacteria, mould, and soap residue building up inside the drum, door seal, detergent drawer, or the internal pipework. Modern washing machines are particularly prone to this because low-temperature eco cycles — while great for energy bills — do not get hot enough to kill bacteria or flush away detergent deposits effectively.
Left untreated, the smell can transfer to your freshly washed laundry, making clothes smell worse coming out of the machine than they did going in. Working through the steps below should resolve the problem completely.
Causes
- Mould and bacteria on the door seal — The rubber gasket around the door traps moisture, lint, hair, and detergent residue after every wash. This warm, damp environment is ideal for mould and bacteria to grow, and it is the single most common source of bad smells in front-loading machines.
- Residue buildup inside the drum and sump hose — Repeated low-temperature washes allow soap scum, fabric softener, and organic matter to coat the inside of the drum and the internal hoses. Over time this residue becomes a breeding ground for odour-causing bacteria.
- Blocked or dirty detergent drawer — The detergent drawer and its housing collect undissolved powder and liquid softener, which go stale and develop a musty smell. A partially blocked drawer can also cause detergent to sit and ferment rather than being flushed into the drum.
- Stagnant water in the pump filter — The pump filter at the bottom front of the machine catches fluff, coins, and debris. If it is not cleaned regularly, trapped water becomes stagnant and produces a foul, sometimes eggy odour that spreads through the machine.
- Leaving wet laundry in the drum — Leaving washed clothes sitting in a closed drum for more than an hour or two allows mildew to develop on both the laundry and the drum surfaces. The smell can then linger in the machine even after the clothes are removed.
- Using too much detergent or softener — Excess detergent does not rinse away cleanly and instead coats internal surfaces, providing food for bacteria. This is a particularly common issue when using non-concentrated detergents in machines designed for high-efficiency formulas.
Step-by-Step Fix
- 1
Clean the door seal thoroughly
Pull back the rubber door gasket and inspect the fold all the way around. Use a damp cloth soaked in a solution of equal parts white vinegar and warm water to wipe away any visible mould, black residue, or debris. Pay close attention to the bottom of the seal where water pools. Dry the seal with a clean cloth when finished.
- 2
Remove and clean the detergent drawer
Pull the drawer out fully — on most Siemens models, press the small release tab at the back of the softener compartment to release it completely. Rinse all compartments under warm running water and use an old toothbrush to scrub away any caked-on residue. Also clean inside the drawer housing in the machine itself, as mould often grows on the roof of this cavity.
- 3
Clean the pump filter
The filter is located behind a small panel at the bottom front of the machine. Place a shallow tray and some towels underneath before opening it, as water will spill out. Unscrew the filter cap slowly, let the water drain, then remove the filter and rinse it under the tap. Check the filter housing for debris and wipe it clean before refitting.
- 4
Run a hot service wash
With the drum empty, select the hottest programme available — ideally 90°C — and add a proprietary washing machine cleaner, or use 250ml of white vinegar poured directly into the drum. This high-temperature cycle dissolves grease and soap deposits and kills bacteria throughout the internal pipework and drum. Run this cycle to completion.
- 5
Wipe down the drum interior
Once the service wash has finished and the drum has cooled, wipe the inside of the drum with a dry microfibre cloth to remove any loosened residue. Leave the door open for at least an hour afterwards to allow the drum and seal to dry out completely.
- 6
Check the drain hose position
If the drain hose is inserted too far into the standpipe or sits too low, dirty water can siphon back into the machine and cause persistent smells. The hose end should sit no lower than 60cm from the floor and no higher than 100cm. Consult your Siemens installation guide for the correct routing if you are unsure.
- 7
Adjust your washing habits going forward
Reduce the amount of detergent and softener you use — most people use significantly more than needed. Switch to a liquid detergent if you currently use powder, as powder is more likely to leave residue. Make a habit of leaving the door and drawer slightly open between washes to allow air circulation and prevent moisture from building up.
When to call a service technician
If you have completed all the steps above and the smell returns within a few washes, or if the odour is particularly strong and sulphurous rather than musty, there may be a fault with the drain pump or a blockage deeper in the internal pipework that is causing water to stagnate inside the machine. These components are not straightforward to access without dismantling the appliance.
You should also contact a service technician if you notice any water remaining in the drum after a cycle ends, as this suggests a drainage fault that will continue to cause smell problems and could eventually lead to further damage. A technician can inspect the pump, check the internal hoses, and clear any blockages safely.
Prevention
Keeping your Siemens washing machine smell-free long term comes down to a few consistent habits. Run a hot 90°C service wash at least once a month, always leave the door and detergent drawer ajar between uses, and wipe the door seal dry after the last wash of the day. Use the correct amount of detergent for your water hardness and load size — the dosing guide on the detergent packaging is a good starting point. Clean the pump filter every one to three months depending on how frequently you use the machine.
The parts most commonly replaced when smell problems are linked to a component fault are the door seal (gasket), the detergent drawer assembly, and the drain pump. If any of these are visibly damaged, cracked, or heavily stained beyond cleaning, replacing them will make a significant difference.
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Frequently Asked Questions
Why does my Siemens washing machine smell even after I've cleaned it?
If the smell returns quickly after cleaning, the most likely cause is that bacteria have become established deep inside the drum bearings, sump hose, or drain pump where surface cleaning cannot reach. Running a 90°C service wash monthly and leaving the door open between uses will gradually reduce the bacterial load. If the problem persists despite this, a service technician can inspect the internal components.
Can I use bleach to clean the inside of my washing machine?
A small amount of diluted bleach can be effective at killing mould, but it should be used with caution. Never mix bleach with vinegar or other cleaning products, and always run a full rinse cycle afterwards to clear any residue. For regular maintenance, a proprietary washing machine cleaner or white vinegar is safer for the rubber seals and internal components.
Why do my clothes still smell after washing?
If laundry comes out of the machine smelling musty or sour, the machine itself is almost certainly the source. Bacteria and mould inside the drum transfer to fabrics during the wash. Clean the machine thoroughly using the steps above, and rewash the affected laundry on a higher temperature if the fabric care label allows it.
How often should I clean my Siemens washing machine to prevent smells?
As a general rule, run a hot service wash once a month, clean the detergent drawer and door seal every two to four weeks, and check the pump filter every one to three months. If you do a lot of low-temperature washes or wash heavily soiled items regularly, clean more frequently.
Does fabric softener cause washing machine smells?
Yes, fabric softener is a significant contributor to smell problems. It is thick and oily, and excess softener coats the drum, seal, and internal hoses rather than rinsing away cleanly. Try reducing the amount you use, or switch to dryer sheets as an alternative. If you do use softener, the monthly hot service wash is especially important to flush away the buildup.