Greywater (What is it and Why use it?)

Greywater is wastewater from houses or commercial buildings. It is produced by activities like laundry, showers, and washing the dishes. Basically, all of the wastewater from a building that does not come from a toilet is considered greywater.

It contains fewer pathogens than black water, which is sewage waste. That means it can be reused for activities like watering the lawn, but it can not be consumed by people or pets. Overall, greywater makes up more than half of the wastewater from the average household. Most households’ greywater makes up 50 to 80% of the water waste.

Greywater vs Blackwater

Blackwater is sewage water. It contains urine and fecal matter which is harmful to consume. Blackwater contains more organic material than greywater. Some studies say kitchen wastewater is considered blackwater too.

Research has found the wastewater from kitchens typically has protein and fats that can be harmful to plants. Blackwater needs to be treated at a sewage treatment and should not be used around plants or animals.

How Does Greywater Help the Environment?

Reusing greywater reduces the demand for fresh clean water and the amount of water that has to be transported and treated. Here’s an overview of all its benefits.

1. Freshwater Conservation

Using greywater lowers the amount of freshwater used in a household. Greywater can be used to flush toilets and water plants.

If the plants are going to be eaten, the water should not touch the edible part of the plants in case there are contaminants in the water. This can reduce the amount of freshwater coming into a house and will help regions in dry climates or the areas experiencing drought.

2. Reduce the Amount of Water Wasted

Catching greywater before it goes down the drain will reduce the amount of water that is dumped into the sewage. This lowers unnecessary waste.

It can reduce the amount of water wasted in a household by half. Saving even just a little water before it is dumped into the sewage water will conserve resources.

3. Less Energy Consumption

The less freshwater that is being used in a house means less energy being used to pump the water into the house. Reusing water also reduces the amount of water that has to be pumped into the water treatment facility and treated. This uses less electricity, which cuts down on fossil fuel use and reduces greenhouse gas emissions.

4. Fewer Chemicals Used in Water

The less water that is sent to sewage plants, the fewer chemicals will be used to treat the water. This is good for the environment because it reduces the demand for chemicals used to treat the water.

Lessen the water that needs to be treated and it lowers the number of chemicals needed to do the job. Reusing water and lowering the amount sent to treatment plants also lowers the risk of the sewage processing companies accidentally dumping chemical waste. It lowers the cost too.

Greywater can be used to water lawns and other plants. The nutrients in the water act as a natural fertilizer and reduce the need to spray yards with chemical fertilizers.

5. Reusing Nutrients

Kitchen and bathwater hold a lot of organic material that can be beneficial to plants. Unlike blackwater, which can house diseases like e. Coli, greywater can have material that can help plants grow.

This does not apply to greywater that has harsh cleaning chemicals or other potential contaminants in it. Capturing kitchen water and bathwater to release into the yard will reduce the need for freshwater to be pumped up to do the same job. It will also keep the grass greener without costing the household any extra money.

6. Naturally Filters Water

When greywater is used to water plants it is filtered by the plants and soil. Most toxins are filtered out naturally through the soil. Unless there are excess amounts of toxins, this should not be harmful to the soil or organisms that live in it.

7. Recharges Groundwater

Since the greywater is filtered by the soil, it moves down and replenishes the dirt as it goes. The water will also replenish waterways such as rivers and underground aquifers.

8. Adds Beauty to the Landscape

Collecting and redirecting greywater into yards and gardens will help the landscape stay moisturized and pretty. This can be helpful for wildflowers and grasslands as well.

When used with mulch and drip irrigation, the water can last longer and help grow trees and other plants in the yard. This will help beautify the landscape while conserving water and helping the environment.

Uses for Greywater

The easiest use for greywater is to have it piped directly outside and used for decorative plants or fruit trees. It can also be used to water vegetable plants too as long as it does not get used on the edible parts.

If greywater is going to be used that way it is important to use products that are plant-friendly. They should not have a lot of salt, boron, or chlorine bleach since the buildup of these can damage plants.

Guidelines for Greywater

Greywater has organic matter in it so it requires different guidelines than freshwater. It should not be stored for more than 24 hours since the nutrients will start to break down and smell bad. If it is stored for too long it can start to grow bacteria. 

Try to minimize the contact greywater has with humans. It can potentially contain pathogens that can be dangerous for people before it is filtered.

Do not allow greywater to pool or runoff. It should be allowed to soak into the soil and the plants. The amount of greywater pumped out to plants should match the plant’s needs. If an underground greywater system is built, it is important to know how well water soaks into the soil so the irrigation system routes the water to the right spots.

Simple systems will require less maintenance so they should last longer. Installing a 3-way valve will allow for switching between the greywater system and the sewer system.