We use a lot of water: to flush our toilets, cook our food, fill our bathtubs, water our plants, wash our clothes, and brush our teeth. An average family of four in the U.S. uses about 400 gallons of water each day, according to the U.S. Environmental Protection Agency, and about 120 of those gallons are wasted. but a lot of the water we use can be repurposed. Reusing water is especially important as climate change raises temperatures and diminishes available water supply. And that’s where greywater comes in.

Greywater is the lightly used water from showers, bathtubs, sinks, and washing machines in the home that often just spirals down the drain, flowing into sewers. While this water is a pollutant when released into natural water bodies, it is a beneficial source of water and nutrients for garden and household plants alike, and can be repurposed in many ways. Greywater can be safely used if it contains traces of grease, hair, dirt, food, and some cleaning products, but not if it contains feces, so all water from toilets or from washing diapers – called “blackwater” – is off-limits.

Reusing greywater – whether through a simple, DIY mechanism or a professional system installed in your home – can reduce water waste by up to 40%. As droughts become more pervasive due to climate change – like the megadrought in the U.S. West that scientists estimate is 42% more extreme due to climate change – many regions are implementing strict limits on water use, including Los Angeles, Ventura, and San Bernardino counties in California, where millions of people will be impacted by new orders next month that limit outdoor water use to only one day a week. Greywater systems make water available for outdoor use even in the face of such restrictions, insuring that your gardens and indoor plants won’t become casualties of water shortage. Greywater systems also save money: if you’re reducing your water use by 40%, you’re also slashing your water bill by the same amount.

Greywater is primarily used to water ornamental plants like trees, shrubs, flowers, and native grasses, but can also be used to water vegetable plants and other garden edibles as long as the water touches only the soil and does not come into contact with the edible part of the plant that will be harvested. When watering plants, make sure to use water that doesn’t contain products harmful to the soil, like bleach or high amounts of salt.

If gardening isn’t your forte, use water without grease – like wastewater from laundry machines – to wash the car. Collected greywater can also be used to “bucket flush” toilets instead of using clean water, which serves little purpose for flushing our waste.

Professional greywater systems are often expensive to install, but simple DIY systems can be very functional and produce comparable savings. Greywater Action is a group of educators dedicated to developing new codes and incentives to reduce water use in communities by utilizing greywater, and who develop and share designs for low-tech, affordable greywater systems for residential use. They also offer online workshops and courses about installing these systems yourself – take one to find out which at-home system is best for you, given the construction of your home, your personal water usage, and your budget.

Greywater Action has many designs for greywater systems that require minimal materials and maintenance, including a simple solution for repurposing spent water from laundry machines. Since you won’t necessarily need all of the used laundry water for your plants, installing a diverter valve is a good way to switch between the greywater and sewer/septic systems. Connect the machine’s discharge hose (from which the water is pumped out) and attach it to the diverter valve. On the greywater side, use a hose to direct the water flow into a large plastic drum, then insert a spigot or hose into the bottom to dispense the water for yard use – or, use the valve to divert water directly to an irrigation system in the yard.

More elaborate, professional systems can reconfigure household plumbing to reroute water from all applicable sources, but can cost up to $10,000. While more expensive, these systems can save between 10,000 and 50,000 gallons of drinking water each year – savings which are especially important in regions like California facing unprecedented drought. Greywater Action has a directory of companies and individuals who have completed training and can professionally install greywater systems. Find a trained professional to help build a system that works for you, or look into other local services.

Water security – both sustainable supply and clean quality – is a critical aspect in ensuring healthy communities. Yet, our world’s water resources are being compromised.

Today, 80% of our wastewater flows untreated back into the environment, while 780 million people still do not have access to an improved water source. By 2030, we may face a 40% global gap between water supply and demand.

The World Economic Forum’s Water Possible Platform is supporting innovative ideas to address the global water challenge.

The Forum supports innovative multi-stakeholder partnerships including the 2030 Water Resources Group, which helps close the gap between global water demand and supply by 2030 and has since helped facilitate $1Billion of investments into water.

Other emerging partnerships include the 50L Home Coalition, which aims to solve the urban water crisis, tackling both water security and climate change; and the Mobilizing Hand Hygiene for All Initiative, formed in response to close the 40% gap of the global population not having access to handwashing services during COVID-19.

Want to join our mission to address the global water challenge? Read more in our impact story.

Even without an established system, you can reuse greywater every day! Collect water by placing buckets in the shower while the water is warming up, or nest a bowl underneath a colander when washing produce or draining pasta. Save the water from steaming vegetables or whatever is leftover in dog/cat water bowls. Even leftover coffee can be used to water acidity-loving plants, like begonias and azaleas.

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This article is published in collaboration with EcoWatch

The views expressed in this article are those of the author alone and not the World Economic Forum.

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