Why is My Water Leaving Green Stains

Why is My Water Leaving Green Stains and How to Remove It?

Water is an indispensable resource in our lives. However, at times, we may encounter unsettling green stains in sinks, bathrooms, or other areas at home or in workplaces, caused by the presence of copper content in water reacting with oxygen and forming green copper oxide deposits. This issue is not uncommon, and many people have experienced it. These green stains not only pose cleanliness concerns in our living spaces but also raise a series of questions: why is my water leaving green stains? Is it harmful to our health? How can we address this issue to maintain a clean and comfortable living environment?

In this article, we will delve into the reasons why water leaves green stains and provide solutions to this problem. Whether you are a homeowner or a manager in a commercial establishment, understanding and addressing this issue is crucial for maintaining water quality and hygiene. Next, we will explore copper and water quality issues, analyze possible causes, discuss hazards and effects, and offer solutions and recommendations. Let's explore how to tackle the challenge of water leaving green stains together.

What is water leaving green stains?

Green water stains in the sink are typically precipitates of Copper Oxide. When water with a high copper content comes into contact with copper pipes and oxygen, copper dissolves and undergoes an oxidation reaction, forming green copper oxide particles. As a result, green traces or stains are left on surfaces that come into contact with water. This phenomenon is commonly observed in sinks, bathtubs, faucets, and other places, especially when there is a high copper content in the water or water quality issues exist.

What causes my water leaving green stains?

Copper Materials in the Water Supply System and Fixtures

Pipe Corrosion: If your water supply system uses copper pipes and fittings, they can corrode over time. Corrosion can lead to the release of copper ions into the water, turning it green and leaving marks on sinks, bathrooms, or other surfaces.

Water Treatment Agents


Some water treatment agents and additives may contain copper. These additives are introduced during the water treatment process to control water quality or maintain the health of the pipes.

Water pH Levels

The acidity or alkalinity (pH) of water can affect its corrosiveness, which, in turn, affects the stability of metal surfaces like copper pipes or fittings. Acidic water has a lower pH (typically below 7) and is corrosive. Under acidic conditions, water is more likely to dissolve copper or other metals from the metal surfaces. Therefore, if your water source or the water in your supply system is slightly acidic, it may lead to copper release into the water and eventually result in green stains.

Water Quality Issues

Water sources can be contaminated by external factors such as industrial wastewater discharges, agricultural chemicals, or natural sources of pollution. Water may also contain other minerals or elements (such as iron, manganese, calcium, magnesium) that react with metal surfaces.

Installation Errors

Proper placement of water treatment equipment is essential to ensure its effective operation. If the equipment is installed incorrectly, it may not effectively remove metal elements from the water, leading to staining issues.

Extended Periods of Non-Use


Water systems that are unused for extended periods may stagnate, allowing the growth of microorganisms such as algae or bacteria. These microorganisms can interact with metal surfaces, leading to color and staining problems.

 Is the green staining in water a health risk?

Copper is an essential trace element for human health, and while small amounts of copper are generally harmless to humans, excessive copper in drinking water can have adverse health effects, such as:

Gastrointestinal Discomfort

Drinking water containing copper oxide can lead to gastrointestinal discomfort, including abdominal pain, nausea, vomiting, and diarrhea. This is because copper oxide can have an irritant effect on the gastrointestinal tract at high concentrations.
Liver Issues Long-term consumption of water containing copper oxide can have negative effects on the liver. Although these effects usually require prolonged accumulation.
Copper Poisoning  If the concentration of copper oxide in the water is exceptionally high, long-term consumption can lead to copper poisoning. Symptoms of copper poisoning include headaches, fatigue, dizziness, vomiting, diarrhea, liver damage, and neurological issues.
Health Risks for Children and Infants Infants and young children are at greater risk of copper poisoning because of their smaller body weight and higher sensitivity to copper. High concentrations of copper may negatively impact the growth and development of children.
Developmental Effects Pregnant women exposed to high concentrations of copper oxide over an extended period may have adverse effects on fetal development.

How to remove water leaving green stains?

As mentioned above, we now know the answer to why my water is leaving green stains. So, how to treat water leaving green stains?

Replace Pipe Fittings If you discover corrosion or damage to copper pipes or fittings in your water supply system, which can lead to green stains in the water, it's essential to replace them with fittings that meet health standards.
Adjust pH Levels Adjust the pH of the water to keep it within a neutral or slightly alkaline range. This can be achieved by using water treatment equipment or using alkaline water treatments like baking soda.
Regularly Flush Water If the staining issue is due to water stagnation from long periods of non-use, you need to turn on the faucets and let the water flow for some time to prevent water from lingering in the pipes.
Clean the Stains If stains have already formed, you can clean the green water stains on faucets or sinks using substances like citric acid, vinegar, baking soda, etc.
 Install a Water Purifier or Filter If you find that the primary cause of green stains is water quality issues or you're unsure about the source of these blue-green stains, installing a filter or water purifier can help address the problem.

Here, we recommend the Membrane Solutions® T1-400 tankless reverse osmosis water system, which has been tested and certified by SGS. It uses a 5-stage water filtration process (PP+CTO+T33+RO+UV) to remove up to 99.99% of contaminants, including chloride, microorganisms, heavy metals, lead, viruses, and over 1000 other pollutants. If you want to ensure your water is free from other contaminants and eliminate issues like why my water is leaving green stains, this is the most effective treatment solution!

 Why is My Water Leaving Green Stains

How to prevent my water from leaving green stains?

Regular Maintenance of the Water Supply System Regularly maintaining the water supply system, including fittings, pipes, filters, and water pressure, and testing the functionality of water quality alarm systems helps ensure the health of the water quality and reduces the risks of water quality issues and system failures.
 Water Quality Testing Water quality monitoring is a critical step in ensuring the safety of the water supply system and drinking water. It helps detect potential issues early, reduces water quality-related risks, and ensures people have access to high-quality and safe drinking water. Please note that water quality testing requires specialized knowledge and equipment

In summary, green stains in water may be caused by various factors, affecting not only water quality but also posing health risks to humans. It is crucial to address this issue promptly to maintain water quality and prevent contamination. By installing a reverse osmosis system to filter water, you can ensure that your water is safe, clean, and enjoyable to drink.