A musty smell in your shower is usually caused by moisture build-up, blocked drains, mould growth or trapped debris inside the plumbing system. Hair, soap residue and poor ventilation can create damp conditions that allow bacteria and mould to develop. In some cases, sewer gases from plumbing issues may also contribute to unpleasant odours. Cleaning the drain, improving ventilation and addressing plumbing blockages can help remove the smell and prevent it from returning.If your shower smells musty, the most common causes are trapped moisture, mould or drain build-up. Persistent odours may indicate a deeper plumbing issue that needs professional attention.

Why Showers Develop Musty Smells

Bathrooms are naturally damp environments, and showers experience constant exposure to water, humidity and soap residue. When moisture does not dry properly or debris builds up in drains, it creates ideal conditions for mould, mildew and bacteria to grow. Over time, this can lead to a noticeable musty smell that lingers in the bathroom. While some odours are easy to fix, others may indicate hidden plumbing problems beneath the surface.

Common Causes of Musty Shower Smells

Hair and Soap Build-Up

Hair, soap scum and body oils commonly collect inside shower drains. As this debris breaks down, it can produce unpleasant odours and restrict water pressure. The build-up also traps moisture, which encourages bacterial growth. If drainage is becoming slower as well, it may help to learn more about what’s really blocking your drains.

Mould and Mildew

Poor ventilation allows moisture to remain trapped in the bathroom after showering. This can lead to mould and mildew growth on grout, walls, ceilings and around drains. Mould often produces a damp, earthy smell that becomes stronger over time.

Blocked or Slow Drains

A partially blocked drain can allow stagnant water to sit inside the pipe. This creates unpleasant smells and may indicate a developing blockage deeper within the plumbing system. Gurgling sounds or slow drainage often accompany this issue. You can also read about bad smells from drains and what they mean to better understand the possible causes.

Dry or Faulty Water Traps

Shower drains contain water traps designed to block sewer gases from entering the home. If the trap dries out or is not functioning correctly, unpleasant sewer odours may escape into the bathroom.

Hidden Leaks or Moisture Problems

Leaks behind walls or beneath shower bases can create hidden moisture problems. Damp building materials may develop mould and produce ongoing musty smells even if the shower itself appears clean.

Signs the Problem May Be Serious

While minor odours are often caused by surface issues, some signs suggest a larger plumbing problem. Persistent smells that return quickly after cleaning, visible mould growth, water stains or continuously slow drains may indicate hidden leaks or sewer line issues. If left untreated, these problems can worsen over time and potentially lead to water damage.

What You Can Do About It

Regular cleaning and maintenance can help reduce shower odours before they become serious. Cleaning the drain regularly removes hair and soap build-up. Improving bathroom ventilation with exhaust fans or open windows helps moisture dry more effectively and reduces mould growth. Running water regularly also helps maintain the water trap seal and prevents sewer gases from entering the bathroom. If odours continue despite cleaning, professional plumbing inspection may be required.