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The Different Types Of Water Contamination After A Flood

A flood can be a dangerous experience, whether it’s confined to your basement or a large-scale weather event. In order to stay safe, it’s crucial to understand the different types of floodwater, what floodwaters contain, and how contaminants can affect you.

In addition to the risks of drowning, electrocution and injury that are present in the aftermath of a flood, contamination is a serious threat to your health and must be taken into consideration. In general, there are three types of floodwater you might encounter. Clean water and greywater floods are usually confined to the home, while blackwater floods can happen at home but also on a larger scale, such as the widespread flooding after a hurricane or other severe weather event.

Clean Water

Floodwater that does not post an immediate health threat is known as clean water. Seems obvious, right? Clean water floods can result from malfunctioning appliances, toilet holding tanks, and melting snow and rainwater. Clean water home floods are generally safe for you to clean up yourself, but remember--time is an important factor. Standing clean water can become greywater in as little as 48 hours.


Greywater, or sullage, refers to wastewater that is not contaminated with fecal matter. As far as household wastewater goes, greywater could include water from bathtubs and showers, washing machines, dishwashers, and sinks. It generally contains fewer pathogens than blackwater and can be reused for non-potable purposes, such as toilet flushing. Greywater still contains small amounts of contaminants and can induce illness if ingested.

Floods by greywater can be caused by a weather event, an overflowing plumbing fixture or appliance or even a broken pipe. This type of greywater can saturate carpeting, furniture and drywall. If you experience a home flood with greywater, be cautious when beginning the cleaning process. Wear protective gear such as rubber boots and gloves, and keep children, pets and individuals with a compromised immune system away from the flooded area. If the flood is extensive, such as several inches of water in the basement, it is advisable to hire professionals to safely clean up and decontaminate the area. Cleanup must begin immediately--greywater can become blackwater in as little as 48 hours.


Blackwater refers to wastewater contaminated with human waste or other fecal matter. Blackwater comes from flush toilets and bidets, and contains human waste such as urine and feces as well as toilet paper. Blackwater can also include water from food preparation sinks, dishwashers and other sources. Raw sewage is classified as blackwater. Blackwater is a haven for dangerous bacteria and pathogens that must fully decompose before being released into the environment. It can also be contaminated with dissolved chemicals and particulates, making contact even more dangerous.

When it comes to home flooding emergencies, blackwater floods are the most dangerous and the most destructive. Because of the grossly unsanitary conditions of the water, porous and absorbent items such as carpets, upholstery and drywall are often unsalvageable. Contact with blackwater via ingestion or skin contact can cause illness in both humans and pets.

If you suspect that your home flooding situation involves sewage or blackwater, it is advisable to contact a professional plumber or water restoration expert to assess the situation before attempting to begin remedying it yourself.

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