Why Does My Tap Water Smell? Common Causes, What It Means, and What You Can Do
Understanding why your tap smells, what the different smells mean, and how to address them helps you protect your home and your peace of mind.
Tap water should be clear, odorless, and free of contaminants. When it isn’t, it’s noticeable fast — a strange smell coming from the kitchen sink, bathroom faucet, or utility spigot is unsettling and makes you wonder if the water is safe to drink, cook with, or bathe in. But odors in tap water don’t always mean there’s a serious health hazard. In many cases, they point to specific causes in your plumbing, water heater, supply line, or municipal system that are identifiable and fixable. Understanding why your tap smells, what the different smells mean, and how to address them helps you protect your home and your peace of mind.
Tap water odor isn’t random; the smell usually comes from chemical reactions, biological growth, trapped gases, or build-up inside your system or fixtures, rather than something harmful in the municipal supply. That said, it’s always worth paying attention — recurring or strong odors are clues that something needs attention. In this guide, we’ll walk through the most common smells people encounter, what each means, how to diagnose the cause, and practical steps you can take to correct the issue.
How Water Gets Its Smell: Common Causes Inside and Outside Your Home
Water itself doesn’t have a smell. When you detect an odor, it’s because something has been introduced or developed in the water as it travels from the source to your tap. The source might be your service line, your house plumbing, the water heater, or even your sewer or drain lines near the outlets. Identifying where the odor originates — and when it happens — is key to fixing it.
Municipal water systems treat water to remove contaminants and typically deliver odor-free water. However, as water travels through pipes, it can pick up elements from pipe corrosion, organic matter, chemical reactions, or bacteria living in your hot water tank. Hard water minerals, environmental contaminants, or plumbing material degradation can also contribute to unusual smells. Because odors vary by type, paying attention to the specific smell helps narrow down the cause.
The Most Common Tap Water Odors and What They Mean
1. Rotten Egg or Sulfur Smell
A rotten egg smell is one of the most infamous tap water odors. It’s often described as sulfuric, and people quickly notice it during the first draw of water from a faucet, especially in the kitchen or bathroom.
That smell typically comes from hydrogen sulfide gas — a gas that smells strongly like rotten eggs. Hydrogen sulfide can originate from a few places:
Water heater reaction: Bacteria in the hot water tank can react with magnesium or aluminum anode rods, producing hydrogen sulfide. In this case, the smell is usually stronger from the hot water tap than the cold.
Organic material at the source: If the water supply (well water, for example) contains decaying organic matter, bacteria can produce sulfur compounds before the water ever enters your home.
Chemical reactions in pipes or fixtures: In rare cases, chemical reactions between disinfectant byproducts and pipe materials can form sulfur compounds.
The key clues are whether the smell is stronger with hot water, whether all faucets are affected, and whether it appears suddenly or gradually.
2. Chlorine or “Pool” Smell
Municipal water systems often use chlorine to disinfect water — it kills harmful microbes before water reaches your home. Chlorine normally dissipates quickly and shouldn’t make water smell strongly. However, a noticeable chlorine or bleach-like odor may indicate:
Recently treated water: If the utility has recently flushed lines, treated for algae, or responded to contamination concerns, residual chlorine may be higher. The odor often fades after a day or two.
Low usage: In homes where water sits in pipes for long periods (vacation homes, low-occupancy), chlorine can build up in stagnant water, giving a stronger smell.
Typically, chlorine odors don’t signal danger; they’re a sign of the disinfectant doing its job. Still, if the smell persists for more than a few days, contacting your water provider or a plumber is a good idea.
3. Metallic or “Iron” Smell
Some tap water smells like metal, rust, or pennies. This odor usually suggests that water is interacting with metal components in the plumbing system or that there’s iron or manganese in the supply.
Corroding pipes: Older galvanized steel or iron pipes can corrode internally, releasing metallic taste and odor into the water.
High mineral content: Hard water with elevated iron or manganese levels from well sources or local geology can produce a metallic smell.
Metallic odors are often accompanied by discoloration — reddish, brown, or black tint in the water. While this isn’t always harmful, it’s a strong indicator that pipe condition or water chemistry needs attention.
4. Musty or Earthy Smell
A musty, earthy, or “dirty water” smell often indicates organic matter in the water or microbial growth in the plumbing system. This is common in wells that draw from shallow aquifers with decaying vegetation, or in tanks and reservoirs where organic build-up occurs.
Inside a home, musty smells can come from biofilm growth in the water heater, faucet aerators, or drain traps. Sediment build-up in toilets and drains can also contribute to an earthy odor.
Musty smells tend to be more noticeable after water sits in pipes — for example, first thing in the morning when you run the tap after overnight stagnation.
5. Sewage or Foul Odor
This is the most concerning smell because it signals the possibility of sewage contamination or problems with the plumbing system’s waste side, not the water supply.
A sewage smell from a tap often means:
Dry drain traps: P-traps beneath sinks hold water to prevent sewer gases from entering. If a drain hasn’t been used for a while and dries out, sewer gas can escape into the room, making it smell like sewage.
Sewer line issues: Blocked vents, damaged sewer lines near the foundation, or compromised waste pipes invite sewer gas into the house and can even affect water quality.
Cross-connections or backflow: In rare but serious cases, wastewater can re-enter the potable water system if backflow preventers aren’t installed.
A sewage smell should be treated seriously and warrants immediate professional plumbing inspection.
Diagnosing When and Where the Smell Occurs
Noticing when the smell appears helps pinpoint the cause:
Only hot water smells usually mean the issue is in the water heater.
Only cold water smells suggest the supply line or municipal water is involved.
Both hot and cold smell may point to the main water supply or the entire plumbing system.
Only certain faucets' smell indicates that fixtures, aerators, or traps are the problem.
A smell after a period of non-use often indicates stagnant water or a dry P-trap.
A simple test is to run both hot and cold taps separately and note which produces the smell. Also check other fixtures — bathroom, outdoor faucets, utility sinks — to see if the smell is localized or throughout the home.
Practical Steps to Fix or Reduce Tap Water Odors
Clean or Replace Aerators and Screens
Aerators at the end of faucets trap sediment and can accumulate biofilm. Cleaning them periodically removes build-up that contributes to odors.
Flush the Water Heater
If hot water smells, flushing the water heater periodically helps remove sediment and discourages bacteria build-up. In cases with persistent sulfur smell, replacing the anode rod with one designed for low-odor conditions helps reduce reactions that produce hydrogen sulfide.
Run Taps Periodically
In seldom-used sinks, simply running water for a few minutes daily prevents stagnation and keeps traps full so sewer gases don’t enter.
Use Drain Traps Correctly
Make sure floor drains and sink drains hold water in their traps. If a trap dries out, pour a small amount of water into the drain to reseal it.
Check Supply Lines and Fixtures
Internal corrosion or degraded supply lines can add metallic or musty odors. In older homes, updating plumbing materials (PEX or copper) often eliminates odor problems caused by deteriorating pipes.
Install Filtration or Treatment
If your water supply has high mineral content or certain odors persist, under-sink filters or whole-house water treatment systems reduce taste and smell issues and improve overall water quality.
Address Sewer Smells Immediately
If the smell is clearly sewer-like, avoid using the fixtures until a plumber evaluates the system. A persistent sewer gas odor may indicate a vent blockage, dry traps, or compromised sewer lines — all of which require professional correction.
When to Call a Plumber
Some tap water odor problems are simple to fix on your own — cleaning aerators, flushing the water heater, running faucets, or topping up dry traps. But recurring or strong odors, especially sewage-like smells or those affecting all taps, are best evaluated by a professional plumber.
A plumber can:
Perform pressure testing and supply line inspection
Check the water heater condition and internal build-up
Evaluate sewer vents and traps for proper function
Locate and repair leaks or cross-connections
Recommend filtration or water treatment systems
Professional diagnosis ensures you’re not just masking a symptom — you’re addressing the underlying cause.
FAQ: Tap Water Odors — What Homeowners Should Know
Why does only my hot water smell bad?
If only the hot water smells, the issue is usually inside the water heater — past sediment, bacterial build-up, or chemical reactions with an anode rod.
Is a chlorine smell dangerous?
A mild chlorine odor often comes from municipal disinfectant and is generally not dangerous. It usually dissipates after running the tap for a minute.
What does a rotten egg smell indicate?
A sulfur or rotten egg odor is often caused by hydrogen sulfide gas, which can come from organic build-up in the water heater or the supply line.
Why does my bathroom faucet smell like sewage?
A sewage smell at a faucet often comes from a dry drain trap or from sewer gas entering through a blocked or non-functioning plumbing vent.
Can I fix water odor problems myself?
Some fixes — cleaning aerators, flushing the water heater, running stagnant taps — you can do yourself. Persistent or strong odors, especially sewer-like ones, should be evaluated by a professional plumber.
If you need a licensed, bonded, insured plumber for your Phoenix area leak or your next plumbing project, call MNS Plumbing today.
