In a nutshell
- 🦠Musty smells arise from lingering moisture and detergent residue forming biofilm in seals, drawers, and the sump; microbes release volatile acids that create the odour.
- 🧪 Baking soda (sodium bicarbonate) is a mild alkali and pH buffer that neutralises acidic odours and loosens grime so agitation and rinsing remove it.
- ⚙️ Use it right: add 1–2 tbsp per routine load; run a monthly 60°C maintenance wash with 100–150 g; scrub gaskets/drawers with a light paste, then rinse.
- 🚫 Safety and myths: it’s low-sudsing and seal-safe in modest doses; don’t mix vinegar and baking soda in the same cycle; heavy mould may need manual cleaning and heat.
- 🌬️ Prevention essentials: keep the door and drawer ajar for airflow, wipe seals after heavy loads, and use periodic hot cycles to stop smells at the source.
That sour, mouldy smell from a washing machine is the kind of domestic annoyance that sneaks up on even the most diligent households. Low-temperature cycles, airtight doors, and generous helpings of liquid detergent all conspire to leave residue that bacteria adore. One pantry staple offers a clear, inexpensive fix: baking soda (sodium bicarbonate). As a gentle alkali and odour absorber, it keeps the drum, seals, and detergent drawer noticeably fresher between washes. Used correctly, baking soda alters the conditions microbes rely on, making your machine a less welcoming home for smells. Here’s how the humble powder prevents pong and keeps modern machines in good nick.
Why Washing Machines Smell Musty
Modern machines are superb at water efficiency but notorious for trapping moisture. After a cycle, small pools linger in the sump, door seal, and detergent drawer. Mix that damp with detergent residue and lint, and you get a sticky film—known as biofilm—that hosts bacteria and mould. These microbes release volatile acids and sulphur compounds, the very notes your nose registers as “stale” or “musty”. Short, cool programmes and liquid detergents can leave more un-rinsed surfactants behind, feeding that growth.
Odours are symptoms of microbial build-up, not simply “poor detergent”. The drum itself is rarely the culprit; it’s the hidden crevices where air doesn’t circulate. Tightly shut doors trap humidity, and softeners can amplify film when overused. Left unchecked, the biofilm creeps across the rubber gasket and drawer rails. Addressing the chemistry of that film—and reducing the acidity microbes favour—is the straightforward way to send smells packing.
How Baking Soda Stops Odours at the Source
Baking soda (sodium bicarbonate, NaHCO3) is a mild alkali and effective pH buffer. By nudging wash water towards neutral-to-alkaline, it disrupts the acidic environment that many odour-causing bacteria prefer. It also helps loosen films that cling to metal and polymer surfaces. While it’s not a disinfectant, it does two vital jobs for freshness: it neutralises acidic odours and reduces the tenacity of grime so normal agitation can carry it away. In short, it targets the conditions that allow smells to start.
The powder also assists detergents in slightly harder water by encouraging some minerals to precipitate, which can improve rinse performance. It’s non-corrosive to stainless steel drums and compatible with most modern seals. Still, avoid packing it into crevices; it dissolves best dispersed in the drum or drawer. Note the limits: baking soda won’t remove black mould staining alone, and it doesn’t replace periodic hot maintenance washes. Think of it as the daily newsstand, not the Sunday deep read.
Step-by-Step: Using Baking Soda in Your Wash Routine
For routine loads, add 1–2 tablespoons (15–30 g) of baking soda to the drum along with your regular detergent. This modest dose supports odour control without caking. Once a month, run an empty maintenance wash at 60°C with 100–150 g dispersed in the drum; the warmth helps dissolve residue and freshen the sump. For gaskets and drawers, make a light paste (3 tbsp baking soda with a splash of water), brush it on, agitate with a soft cloth, then rinse thoroughly. Do not mix vinegar and baking soda in the same cycle—they neutralise each other.
Keep the door and drawer ajar between cycles to let moisture escape, and wipe the seal after heavy loads. If you’ve inherited a smelly machine, expect a few treatments before the odour fades—biofilms build in layers. For delicate fabrics, stick to the smaller dose and normal detergent. If you use pods, pop the baking soda directly into the drum so both dissolve efficiently during the main wash.
| Task | Baking Soda Amount | Where to Add | Frequency |
|---|---|---|---|
| Routine load | 1–2 tbsp (15–30 g) | Drum | Every wash as needed |
| Maintenance wash (empty, 60°C) | 100–150 g | Drum | Monthly |
| Seal/drawer scrub | 3 tbsp as a paste | On surface, then rinse | Quarterly or when musty |
Safety, Compatibility, and Common Myths
Baking soda is low-sudsing and suitable for most high-efficiency machines in modest doses. It won’t damage stainless drums or typical EPDM door gaskets. Still, avoid oversized scoops: excessive powder may leave chalky residue in cool, short washes. If your manufacturer warns against additives, check their guidance and use only during periodic maintenance cycles. Baking soda is not a bleach and not a silver bullet for heavy mould. Severe black staining, especially under gaskets, may need manual cleaning and a hot maintenance programme.
Don’t chase internet myths. Combining vinegar and baking soda inside a single cycle wastes both; use them on separate passes if you prefer an acidic rinse for limescale. There’s no evidence baking soda harms septic systems at normal levels. Its environmental profile is favourable compared with harsh degreasers, and it often reduces the need for fragranced “masking” products. Think balanced routine: sensible dosing, airflow between washes, periodic heat, and targeted cleaning of the nooks where biofilm hides.
Baking soda’s strength is practical, not magical: a cheap, stable powder that adjusts pH, loosens grime, and keeps odours from taking hold. Used in small, regular amounts and backed by the odd hot maintenance programme, it prevents your machine from becoming a swampy echo chamber for yesterday’s wash. When the conditions change, the smells stop. If your laundry room has started to whisper hints of damp, this is the simplest first step. What small change will you make this week to keep your washing machine fresh for the long haul?
Did you like it?4.5/5 (23)