Water Smells Like Mildew? Uncover the Reasons (and Solutions)
Water smells like mildew when bacteria, mold, or organic buildup are present somewhere in your plumbing system or water supply. That musty odor usually means water is sitting too long, reacting with materials in your pipes, or picking up contaminants before it reaches your tap.
The good news? Most causes of water odor are identifiable and fixable. The key is figuring out exactly where that mildew smell is coming from and choosing the right solution before it spreads or worsens.
Why Your Water Smells Like Mildew
That damp, earthy smell typically comes from microbial growth or stagnant water somewhere in the system. Unlike strong sulfur odors, mildew smells are often subtler but just as concerning.
Here are the most common ways water smells like mildew:
Bacteria inside pipes - Biofilm can form along pipe walls, especially in areas where water flow is slow
Mold in drains - Sometimes the smell isn't in the water itself but in the drain trap below the sink
Water heater buildup - Sediment and bacteria inside the tank can create musty odors
Unused plumbing lines - Guest bathrooms or rarely used fixtures allow water to sit and stagnate
Contaminated well water - Organic matter in private wells can introduce earthy or mildew-like smells
If the odor appears suddenly or worsens over time, it's a sign your system needs attention.
Is Mildew-Smelling Water Dangerous?
In many cases, the smell itself isn't immediately harmful. However, it may indicate microbial growth, and that's something homeowners shouldn't ignore.
According to the U.S. Environmental Protection Agency, private well owners are responsible for monitoring their own water quality. If your water hasn't been tested recently, unusual odors are a strong reason to start.
Families with young children, people with sensitive skin, and anyone with a compromised immune system should be especially cautious. Even if the water is technically safe, odor issues can affect taste, comfort, and confidence in your home's water supply.
How to Pinpoint the Source
Before jumping to solutions, narrow down where the mildew odor is actually coming from.
Start with a simple test:
Run cold water only. Then run hot water only
Fill a glass and step away from the sink
Check multiple faucets throughout the house
If only the hot water smells, your water heater may need flushing or servicing. If the smell is stronger near a specific sink but not in the glass, the drain could be the issue.
If every tap smells, the source may be in your main water line or well supply.
How to Eliminate Water Mildew Smell
Once you identify the source, you can take action. Some fixes are simple maintenance. Others require professional plumbing expertise.
DIY fixes to try:
Flush rarely used fixtures to remove stagnant water
Clean sink overflow holes and drain traps
Disinfect faucet aerators
Flush your water heater to remove sediment
These steps can sometimes eliminate water mildew smell if the problem is localized and mild.
Professional Plumbing Solutions
If the odor persists, it's time to look deeper. A licensed plumber can:
Sanitize your plumbing system
Inspect for hidden leaks or pipe corrosion
Perform water quality testing
Recommend whole-home filtration systems
For homeowners searching for lasting home water odor solutions, professional water testing is often the turning point.
When Your Water Heater Is the Problem
Water heaters are a common source of musty smells. Over time, sediment collects at the bottom of the tank. That warm, low-oxygen environment can encourage bacterial growth.
Flushing the tank annually helps prevent odor issues and extends the heater's lifespan. If your system is older or hasn't been maintained, replacing worn components may be necessary to fix smelly plumbing at its source.
If your hot water smells worse than your cold water, don't ignore it. That's a strong clue the heater needs service.
Well Water and Mildew Odors
Homes with private wells face additional risks. Organic material, surface runoff, and bacteria can enter groundwater supplies.
Routine testing is critical. The Penn State Extension water testing guidelines recommend annual testing for private wells, especially after flooding or major plumbing work.
If bacteria or organic contamination is confirmed, shock chlorination or specialized filtration may be required. Long-term mildew odor water solutions often include UV purification or advanced filtration systems designed to target microbial growth.
Long-Term Water Treatment Options
If you're ready for a permanent solution, treatment systems can transform both odor and overall water quality.
Depending on your test results, options may include:
Activated carbon filtration for organic odors
UV purification systems to neutralize bacteria
Whole-home filtration units
Water softeners that reduce mineral buildup, contributing to biofilm growth
If you're unsure how often testing is needed, this guide on how often to test your water can help you stay proactive.
Frequently Asked Questions
Why Does My Water Smell Musty Only in One Sink?
If the odor is isolated, the drain or overflow channel is often the culprit. Cleaning and disinfecting those areas may solve the problem.
Can Mold Grow Inside Plumbing Pipes?
While mold itself rarely grows inside pressurized pipes, biofilm and bacteria can develop along pipe walls and create mildew-like odors.
Does a Brita or Pitcher Filter Remove Mildew Smells?
Basic pitcher filters may reduce minor taste issues, but won't solve deeper bacterial or plumbing-related odor problems. Whole-home systems are typically more effective.
Is It Safe to Shower in Water That Smells Like Mildew?
It's usually not immediately dangerous, but prolonged exposure to contaminated water isn't ideal. If the odor persists, testing and treatment are recommended.
Will Replacing Pipes Fix the Smell?
Only if the issue is caused by corrosion or heavy biofilm buildup. A professional inspection helps determine whether replacement or treatment is the better option.
Fresh, Clean Water Starts Here
If your water smells like mildew, you don't have to live with uncertainty. The odor may stem from bacteria, stagnant plumbing, a neglected water heater, or well contamination, but every one of these problems has a clear solution.
Tim Beil Plumbing helps homeowners identify the exact cause, recommend the right treatment, and restore confidence in their water supply. With professional testing, advanced filtration systems, and decades of trusted service, we deliver results that last.
Ready to breathe easy every time you turn on the tap? Contact us today to schedule your water test or consultation.
