Duke SmartHome Graywater Reuse System

gray wa·ter [noun: greywater]

the relatively clean waste water from baths, sinks, washing machines, and other kitchen appliances.


Daily, each person uses roughly 30 gallons of graywater. For a four-person household, that's 120 gallons per day and 3600 gallons per month per household of graywater. If we could get back just 50% of that, it would provide savings of roughly 21,000 gallons per year for a household of four people. This project intends to use the Duke SmartHome as a case study to develop a prototype that can aid in water conservation. The scope could later be expanded to implement this product in residential homes.

Project Summary

In order to prevent graywater waste in homes, my team (Ale Ferrara and Minhaz Islam) and I proposed a Graywater Reuse System. We took advantage of the cycles in water quality that occur in graywater sources and designed a mechanism that diverts water to storage or sewage according to its quality. After researching the various parameters that control the characterization of water as 'graywater', we decided to focus on 3 vital parameters: conductivity, pH and turbidity. Before we began working on the design, we brainstormed the various risks associated with the project. We used the countermeasures developed in this session to create a device schematic (below) to outline our plan. An initial sand filter clears large debris, and then a series connection of transmitters and solenoid valves provide pass-fail test for vital parameters such as conductivity, pH, and turbidity, resulting in the cleanest graywater output possible.