Borewell Water Smells Bad in Chennai? Here’s Why It Happens
Borewell water smells bad in Chennai mainly due to dissolved gases, bacteria, and groundwater pollution. Deep borewells often contain hydrogen sulphide gas, which causes a strong rotten-egg smell. Iron and sulphur bacteria mix with this gas, forming slime inside pipes and tanks, worsening the smell.
In many areas, sewage leakage and septic tank overflow contaminate groundwater, especially during the monsoon season. Chennai’s soil conditions and overuse of groundwater also contribute to the buildup of minerals in stagnant borewells, leading to foul-smelling water.
Why Borewell Water Smells Bad in Chennai
Borewell water smells bad in Chennai because groundwater contains high levels of minerals, gases, and bacteria. One common reason is hydrogen sulphide gas, which causes the familiar rotten-egg smell many people notice when they open the tap. This gas is mainly produced by anaerobic bacteria, which thrive in low-oxygen environments such as deep or poorly ventilated borewells, and release foul-smelling gases as they break down organic matter. This problem is more common in deep or poorly ventilated borewells, where water remains stagnant for long periods.
On top of this, Chennai’s crowded neighbourhoods, coastal soil, heavy groundwater use, and occasional sewage or septic tank leaks further pollute the water and encourage the growth of other odour-causing bacteria. Sulphur bacteria and iron bacteria are also commonly found in borewell water; sulphur bacteria add to the rotten or sulphur-like smell, while iron bacteria create earthy or metallic odours along with slimy deposits in pipes and tanks. As a result, many homes experience frequent, strong odours in their borewell water.
What are the factors that cause a bad smell in water?
- Rotten egg–like smell from deep water – Water stored deep underground without air starts giving off a rotten egg smell, especially when you first open the tap.
- Slimy buildup in pipes and tanks – Dirty layers form inside borewells, pipelines, and overhead tanks. This slime causes a bad smell and makes the water feel unpleasant.
- Sewage or septic leaks – Leaks from nearby drains or septic tanks can mix with borewell water, leading to very strong and unbearable smells.
- Empty plots nearby – Empty plots often collect garbage, sewage overflow, and stagnant rainwater. Over time, this polluted water seeps into the ground and mixes with borewell water, causing foul and unpleasant smells.
- Anaerobic bacteria growth – In low-oxygen conditions within deep borewells, pipelines, and tanks, anaerobic bacteria grow and produce gases such as hydrogen sulphide, which creates a strong, rotten, sulphur-like smell in water.
- High minerals in water – When water has high iron or similar substances, it smells metallic, earthy, or sulphur-like and stains pipes and tanks.
- Stagnant water – When water sits still in tanks, borewells, or pipes without flowing, it can start to smell bad as dirt and germs grow inside.
Common Water Sources Used in Chennai Homes
In Chennai, homes get water from borewells, municipal (metro) supply, tankers, and rainwater harvesting systems, and each can develop a bad smell if not maintained properly. Borewell water, the most common source, often has a rotten-egg or metallic odor due to underground gases and minerals. Metro water can start smelling if it mixes with borewell water or stays too long in overhead tanks.
Tanker water may carry a foul smell if the source is dirty or the tanker is not cleaned regularly. Even rainwater harvesting systems can produce unpleasant odors when filters and storage tanks are neglected, allowing dirt, leaves, and bacteria to build up. Regular cleaning and proper maintenance are essential to keep water fresh and odor-free.
How Foul-Smelling Borewell Water Affects Homes and Structures
- Bad smell during daily use: The strong rotten-egg or metallic smell makes bathing and washing very uncomfortable.
- Stains and marks: Water with iron can leave brown or yellow stains on sinks, taps, tiles, and utensils, making them look dirty even after cleaning.
- Damage to pipes and tanks: Dirt, bacteria, and mineral buildup slowly damage pipes, taps, and overhead water tanks, leading to rust and leaks.
- Appliance problems: Water heaters, washing machines, and dishwashers can become clogged over time, leading to poor performance or breakdowns.
- Health and hygiene issues: Smelly water often indicates the presence of bacteria or dirt, which can affect cleanliness and pose health concerns for the family.
Key Water Quality Parameters to Test for Smell Issues
- Hydrogen Sulphide Levels: Detects the presence of rotten-egg gas, which is the most common cause of foul odour in borewell water.
- Iron and Manganese: Excess can cause unpleasant odors and colours and contribute to bacterial growth.
- Sulphur Bacteria and Iron Bacteria: Determine microbial contamination that creates slime and odor in water.
- Anaerobic Bacteria: Identify bacteria that grow in low-oxygen conditions and produce gases such as hydrogen sulphide, causing strong, rotten, sulphur-like smells in borewells and stored water.
- pH & Hardness: Excessive pH levels or hard water can contribute to odor & taste problems.
- Total Dissolved Solids (TDS) and Organic Matter: Measures overall mineral and organic content that may contribute to smelly tap water and bacterial growth.
When Should Chennai Homes Test Borewell Water And Get It Treated
Chennai residents should test their borewell water whenever they notice a bad smell, unusual taste, or a change in colour. Foul odours are commonly caused by bacterial activity in groundwater, especially anaerobic bacteria that grow in low-oxygen conditions inside deep borewells, pipelines, and overhead tanks. These bacteria release gases such as hydrogen sulphide, which create a strong rotten-egg or sulphur-like smell. Iron and sulphur bacteria can also produce earthy or metallic odours and form slimy layers inside tanks and pipes. Water testing becomes even more important during the monsoon season, after nearby construction work, or when water in overhead tanks remains stagnant for long periods.
Homes that depend mainly on borewell water should have the water tested at least once a year for harmful gases, iron, and bacterial contamination. To prevent bad smells, proper treatment methods are essential. Aeration introduces oxygen into the water, helping foul gases escape and stopping anaerobic bacteria from surviving. Ozonation further helps in improving the quality of the water by eliminating bacteria causing odor and odor itself, which leaves no chemical residue. Such regular testing by either aeration or ozonation helps in maintaining borewell water clean, safe, and odor-free for drinking purposes.
Where to Go for Reliable Borewell Water Testing in Chennai
- Certified Labs: NABL-certified and state-approved laboratories provide accurate testing for hydrogen sulphide, iron, sulphur smell in borewell water, TDS, pH, and other factors that cause odours in water.
- Authorised Agencies: There are private water-testing centres and CMWSSB lab centres where water can be tested, and the appropriate process can be followed to eliminate the smell from borewell water.
Expert Borewell Water Smell Treatment Solutions – WaterSparks®
- Install the right water solution for your home: Choose a WaterSparks system designed to remove bad smells, iron stains, and other issues that make borewell water unpleasant.
- Get fresh water at every tap: Our whole-house filtration systems clean the water before it reaches your overhead tank, taps, and home appliances.
- Use clean and safe water every day: No more smelly water, ugly stains, or worry about germs in the water you use for bathing, washing, and cooking.
- Get expert help and regular service: Water Sparks provides routine checkups, maintenance, and expert advice to keep your water clean, fresh, and safe year-round.
Why does my borewell water smell like rotten eggs when I first open the tap?
This usually happens because of hydrogen sulphide gas, which develops in borewell water that stays unused for several hours. The smell is more noticeable when you first open the tap in the morning or after a long gap.
Good to know:
If the smell goes away after running the water for a few minutes, the issue is likely in your pipes or overhead tank.
If the smell continues, the source is probably your borewell water.
My water smells metallic and leaves brown stains. Are these connected?
Yes, they are connected. A metallic or “rusty” smell is often caused by iron in borewell water. Many areas in Chennai have naturally high iron levels in groundwater. When iron comes in contact with air, it causes brown or yellow stains on bathroom tiles, taps, clothes, and wash basins.
An iron removal system can effectively solve both the smell and staining issues.
What is the best method to remove bad smell from borewell water?
There are two commonly used professional methods:
Aeration:
This process mixes water with air to release trapped gases that cause foul smells. It is a cost-effective solution for odor problems.Ozonation:
This advanced treatment uses ozone to remove smells and kill odor-causing bacteria. It also improves overall water quality without adding chemicals.
The right option depends on your water test results.
Can my regular RO purifier remove the bad smell from borewell water?
Most regular kitchen RO purifiers are designed only for drinking water and cannot handle strong odors at the source. At best, they may reduce the smell slightly, but the problem will continue in bathrooms, washing machines, and other taps.
For complete odor removal, a whole house water treatment system or an activated carbon filter installed at the main water inlet is recommended.
Why does borewell water smell worse during the rainy season?
During the Chennai monsoon, rainwater can carry organic waste or sewage into borewells—especially if the borewell is not properly sealed. This increases bacterial growth, which leads to stronger and more unpleasant smells.
Tip for homeowners:
If you live in areas like T. Nagar, Adyar, or other crowded neighborhoods, check your borewell casing and surroundings to prevent rainwater contamination.
Why Choose WaterSparks?
Backed by over 25 years of expertise in the Chennai water treatment industry, WaterSparks has deep insight into the geological and chemical complexities of South Indian groundwater. We go beyond simply supplying filters.we design and deliver engineered solutions such as Whole House RO Plants and Iron Removal Systems, precisely customized through detailed analysis of your water’s TDS, iron content, and bacterial presence. Our proven experience ensures a reliable flow of clean, safe, and odor-free water for your home or facility.
For Residential and Commercial Water Treatment Solutions, contact WaterSparks® at +91 98843 66644 or +91 98842 57744.