Why Does My Water Smell? Common Causes and Fixes
Water odors usually come from one of three sources: naturally occurring minerals and organic matter, treatment byproducts like chlorine, or bacteria growth inside pipes, hot water tanks, or appliances. Most odors are not a health concern, but they can point to a maintenance issue worth addressing. Here are the most common water odors, what causes them, and how to fix each one.
Common Water Odors and Causes
1. Mustiness
When water sits in piping or an appliance for a long period, you may smell, or even taste, mustiness in the water. This water is safe to consume, but if the odor bothers you, flush your taps to clear the stale water from the lines. Algae outbreaks or certain weather conditions can also contribute to an earthy or musty taste in water systems that draw from surface water sources. When this happens, the water engineers at your local utility will adjust the treatment process to address the odor.
2. Rotten Eggs or Sulphur Smell
Water held in a poorly maintained hot water heater can grow sulphur bacteria and begin to smell like rotten eggs. This usually happens when the hot water tank has not been flushed regularly, so you'll typically notice the smell only in hot water rather than cold. Flush your hot water tank according to the manufacturer's instructions to clean the holding tank and remove the odor.
3. Sewage or Drain Smells
Drain smells can sometimes give the impression that your home's water itself smells foul, when the actual source is bacteria building up from decaying matter inside the pipes. A range of organisms, including algae, fungi, and various bacteria, can grow in the dark, damp interior of dirty plumbing and create a musty or sewage-like smell.
To check whether the odor is coming from the water or the drain, fill a glass with water and step away from the sink before smelling it. If the water itself doesn't smell, the issue is likely in your drain or plumbing rather than your water supply.
If the water in the glass does smell like sewage, the water supply or your home's plumbing system may be to blame. Two effective ways to remove odor from water at the tap are activated carbon filters, which absorb organic compounds, and reverse osmosis systems, which filter out a broader range of contaminants. If the smell persists after trying these methods, or if flushing your lines doesn't resolve it, contact your water utility to rule out a supply-side issue, or call a licensed plumber to inspect your home's plumbing.
Water Treatment Devices
Water filtration devices can also cause odor or taste issues if they are not maintained according to the manufacturer's guidelines. Filters that go past their recommended replacement schedule can start to harbor the same bacteria and organic buildup they're meant to remove.
Odor removal from water is generally handled through activated carbon filtration, oxidation-reduction, or aeration. Aeration works well when the contaminant is a gas, such as hydrogen sulphide. Chlorine is the most widely used oxidant for odor removal, though it's only mildly effective on its own. Oxygen and potassium permanganate are also mild treatments. Ozone and chlorine dioxide are the most effective oxidizers for eliminating odor from water.
How well activated carbon performs depends on how much organic matter is present in the water. If the odor is caused by hydrogen sulphide specifically, a greensand filter or a degasifier is a better option. Greensand filters use a manganese oxide coating that oxidizes hydrogen sulphide gas into solid sulphur particles, which are then filtered out of the water. Degasifiers work by physically releasing hydrogen sulphide gas from the water, reducing the odor at the source.
Frequently Asked Questions
What causes a rotten egg smell in water?
A rotten egg smell is typically caused by sulphur bacteria growing in a hot water heater that hasn't been flushed regularly. It usually shows up only in hot water, not cold.
Is musty-smelling water safe to drink?
Yes, musty-smelling water from sitting in pipes or appliances is generally safe to drink. If the taste or smell bothers you, flushing your taps will usually clear it.
Why does my water smell like sewage?
A sewage smell is often caused by a nearby drain rather than the water itself. Fill a glass of water away from the sink and smell it directly. If the water smells fine, the issue is likely in your plumbing or drain, not your water supply.
How do you remove odor from water?
Activated carbon filters, reverse osmosis systems, and aeration are common methods for removing odor from water. For hydrogen sulphide odors specifically, a greensand filter or degasifier is more effective.
What is the most effective treatment for hydrogen sulphide odor?
Greensand filters and degasifiers are the most effective treatments for hydrogen sulphide odor, since they target the gas directly rather than masking it. Ozone and chlorine dioxide are also highly effective oxidizers.