What Is Grey Water and How Can You Use it?

what is grey water

According to the Environmental Protection Agency, an average family unit uses 300 gallons of water daily. This has resulted in limited available and accessible fresh water and has prompted the need for reusable water. This is where grey water comes in.

Grey water is domestic wastewater free of fecal contaminants. In homes and offices, any water from, dishwashers, showers, bathtubs, washing machines, kitchen and bathroom sinks, can be classified as grey water.

Its major determinant is that it doesn’t contain fecal matter.

While greywater contains contaminants, its pathogenicity is significantly lower. Because of this, greywater can be evenly treated and reused for various purposes outside of general consumption.

As we examine the question, “What is grey water?” You will learn how greywater provides the much-needed solution to your water shortage problem.

What Is Grey Water Used For? 

You can use gray water for a variety of purposes, and its usage is dependent on the condition of the water itself. Some greywater uses are listed here:

Flushing Toilets

Flushing toilets in households account for about 50% of water usage. Before implementing greywater, we used fresh water to flush toilets. In fact, about 1.6 gallons of water is needed to wash toilets thoroughly. 

So before the idea of greywater, we were wasting almost 2 gallons of drinking water daily on flushing alone. Hence, when greywater became legal in some states, it was quickly adopted. 

Using greywater for flushing toilets comes with a rule —don’t store greywater for flushing because the organic load in the water would multiply over time. This may lead to the development of disease-carrying pathogens.

The best way to use greywater for flushing is to collect it only when there is an immediate need to flush.

grey water irrigation


Homesteaders with lawns, gardens, and farms can use an irrigation system to supply greywater to their plants. The irrigation system can be constructed in such a way that greywater from in-house sources can be dispensed directly to the garden.

Watering the plants should be done using a hose without a sprinkler because you will have to prevent the grey water from touching the leaves, fruits, or any consumable part of the plants.

So when watering, a hose should be used and added directly to the soil. The exit hose for spraying water should have a filter at its outlet, also, its filter must be cleaned every 2 to 3 days to clear debris.

Using greywater for irrigation must be carefully carried out, especially when there are fruit trees in your homestead. Untreated greywater is not supposed to be stored. Any storage of greywater builds grime and increases organic matter, which would cause illnesses if ingested by humans.

Water Source for Husbandry

Homeowners with an animal farm can use greywater to feed their animals instead of potable water. Of course, it means greywater action is subjected to a higher degree of treatment to ensure good water quality.

Before collection, it is crucial that no harsh chemical material is used in the treatment and that the filtration system is top-notch. This combo reduces or even removes any chemical load.

The organic load can serve as a nutrient source for the animals. However, treat grey water to kill off pathogens and avoid poisoning the animals that need water for sustenance.

Benefits of Greywater Use 

Implementing the greywater reuse system has to have more advantages than just water conservation and reducing the water bill. The following are other benefits;

It Reduces Sewage Build-Up

To prevent the complete accumulation of sewage, you would have to live in a house without water. Sewage is a part of life, but the use of greywater reduces its accumulation in the septic system.

Water from washing plates, flushing toilets, bathing, washing clothes, and other household chores that require water would naturally constitute sewage. However, Treatment lowers the pathogen content of sewage in the septic tank and makes it suitable for other benefits

It Increases Available Freshwater 

As stated earlier, when fresh water was used for irrigation, flushing toilets, mopping floors, and other chores that shouldn’t use drinkable water, the world was riddled with fresh water shortage.

Greywater has been a vital substitute for fresh water during chores. This change is essential because 50% of freshwater usage in the homestead that goes to flushing toilets is now available for consumption.


Provides Nutrition for Plants and Animals 

Greywater serves as a nutrient source for both plants and animals. It is advisable to source your greywater from the kitchen sink since it contains more biological condiments. 

These biological condiments when added to the soil through irrigation lines will be broken down into their constituent nutrients. The nutrients are then taken up by the plants. In order to ensure the plants and animals are not hurt by greywater from the sink, it is crucial to avoid using harsh chemicals such as boron. 

For animals, the greywater from the sink should be treated mildly, since it will be going directly to the animals. 

The organic load adds more nutrients to their diet, while still serving as drinkable water. With animals and plants taking up the organic content, the load on the septic tank and sewage system is greatly reduced.

Other sources of greywater are mostly unusable because of soaps, detergents, and cleaning products. The greywater from baths and washing machines has a high chemical load which is detrimental to the health of both plants and animals. 

How Can Greywater Be Treated for Reuse? 

Reusing greywater requires it to pass through specific treatment systems that determine its usefulness. The treatment process begins before the water becomes grey water. 

The homesteader who knows there is a plan to recycle greywater should start treatment by scrutinizing anything mixing up with the water to become greywater.

For example, a person using an off-grid washing machine must avoid using soaps or detergents with harsh chemicals to wash clothes. Knowing fully, he would use the greywater from the washer to irrigate his crops.

After taking these precautions, you can start treatment as follows:

The Physical Separation

Physical separation is a simple system in which a container collects greywater, which will vary according to the volume of water. With time, gravity pulls the solid substances to the bottom. This process is called sedimentation. 

Sedimentation is a simple process that minimizes the use of chemicals for coagulation so that the water is not rendered useless because of chemicals by the completion of treatment.

There are special greywater tanks used for sedimentation. Emptying these tanks often prevents clogging. Even some homesteads add aerators to oxygenate the greywater and make it okay for irrigation.

grey water treatment

Chemical Disinfection

After the liquid part of the sedimentation process has been collected. Water with iodine or chlorine-based products like household bleach, chloramine, calcium, and sodium hypochlorite kills bacteria, viruses, and other harmful microbes.

Solar Disinfection

The solar disinfectant is ultraviolet light (UV rays). The sun heats the water for more than 6 hours a day; this combines with the UV rays to kill bacteria and other microbes.


Filtration is another chemical-free process. Filtration is a physical process that involves passing the chemically treated water through a permeable membrane, like a sieve, or fine sand, to trap the tiny microorganisms in the moisture. Our greywater comes out ready for use.

What are Different Ways to Collect Greywater? 

The collection is the second level of greywater treatment. There are ways of collecting greywater. Some need a container, and others require more complex construction.

Simple Containers

Simple containers like buckets and tanks are placed under the outlets of pipes running from sinks, dishwashers, washing machines, and bathroom showers. These containers are then manually emptied for the next step.

Laundry to Landscape 

The washing machine drain hose joins a distribution channel that ends with an emitter outside, using a 3-way diverter valve. The pipes have filters and other gadgets that will reduce the waste load.

Pumped Irrigation

Here, the simple container (tank) collects greywater. The greywater irrigation lines connect to the tank. So, it would be best to have a pump to move the water through irrigation lines.

Branching Drains

Branching drains rely on gravity to move greywater into different pipes running into separate areas. The tubes are inclined to slope for gravitational pull. Branch drains may require effort to install.

Surge Tank 

The surge tank is a simple collection method. A tank with an outlet at the bottom collects greywater. A hose attached to the outlet manually dispenses greywater. The amount of water would naturally determine the size of the tank.


What are greywater systems? 

Greywater systems are construction or arrangements that collect greywater from the source of use, treat it, and transport it to the point of use.

Is shower water considered greywater? 

Yes, shower water is grey water. It can be a collection of bathwater, water from washing machines, and others.

Is greywater the same as black water?

No, grey water is different from black water. Grey water has no fecal contaminants, while black water has this fecal matter. Black water adds water collected from toilets to grey water, therefore requiring a different means of collection, treatment, and use.

What are standard greywater guidelines? 

Greywater guidelines must be adhered to, as a few states do not even support using greywater. Different states with their jurisdiction have policies.

Don’t store greywater water for any period; treat or use it immediately after it is collected. Treating greywater starts with maintaining caution with what we wash and bathe. 

The soap and washing agents we use, mix with the greywater and can complicate usage. Refrain from using greywater with sprinklers to prevent greywater from touching plants’ leaves, fruits, and edible parts. Conduct soil tests if you are using irrigation for salinity and other plants damaging chemicals 

Final Thoughts 

Grey water has dramatically improved the water situation and that is why some states have fully adopted the treatment of greywater for use.

Although some other states still have reservations about the efficacy of greywater, they have implemented guidelines to help everyone utilize it effectively.

Being able to use greywater onsite or at home requires knowledge, plumbing, and a good understanding of greywater recycling systems. With these, many people would not need to rely on the government for their daily needs. 

As a homesteader, remember that adhering to your state’s guidelines concerning greywater use will be your surest path to getting the most out of reusing greywater.