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San Diego State University

Common Experience Water

Greywater/ Rainwater


Problem: Reusable water is wasted when it goes directly into a sewer or water treatment plant rather than being recycled within a household. This water can be used primarily to irrigate yards/plants but instead is thrown away requiring more immediate need to irrigate with potable water. On an environmental level, effluent that is discharged into regional rivers or streams degrades water quality and can be detrimental to existing aquatic life and to the entire ecosystem.


Solutions: Collect this wastewater with greywater recycling tanks (requires installation). Redistribute treated greywater into other applications such as irrigation, pluming, and heating. Collect rainwater with outdoor storage tanks and use this rainwater to irrigate, wash, or even purify and consume.


*More about rainwater [below]


What is greywater? [Definition from Wikipedia]


Greywater, is generally accepted as being wastewater generated from wash hand basins, showers and baths, which can be recycled on-site for uses such as WC flushing, landscape irrigation and constructed wetlands.


* Greywater often (not always) excludes water from laundry, dishwashers, and kitchen sinks due to high levels of chemicals and nutrients (contaminants). Greywater is different from blackwater as it is not considered sewage.


How greywater recycling works.




Why is greywater good?


With a properly connected greywater system, residents can potentially save up to 30% of the water used in their homes. The use of greywater reduces the need to use potable (drinkable) water that is highly valuable to conserve.


How rainwater collecting works.


Diagram from: 


Why rainwater collection a good method of water conservation?


The immediate benefit is minimizing to eliminating the need to irrigate with potable water. The long-term benefit to collecting rainwater is an economic benefit of saving money on water bills.

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