Validating PATH’s prototype design

PATH field tests its new prototype water filter among low-income households in India

Women attempt to assemble HWTS device.

A volunteer family puzzles out how to assemble a device for household water treatment and storage without instructions or external help. Photo: PATH/KFlick.

PATH staff and partners recently completed a three-month longitudinal study to field-test a prototype of a household water treatment filter developed by PATH and Seattle-based Cascade Designs, Inc  (www.cascadedesigns.com). This product was developed on the basis of design guidelines that PATH generated after its extended user testing work in the state of Andra Pradesh. By testing this pre-production (very close to final) prototype in low-income households, we were able to validate the guidelines and gain a clearer understanding about which guidelines can be followed loosely and which ones are nonnegotiable among this target market.

Research methodology

Beginning in September 2010, a team of researchers placed 15 prototypes in low-income households in peri-urban and rural areas near Hyderabad, in Andhra Pradesh. During the first visit, the team focused on ease of assembly and first impressions of the device and the filtered water it provided. After six weeks, researchers visited each household again to learn how they were using it, cleaning it, and integrating the practice of water treatment into their lives.

Water quality evaluations were also performed to track the relative contamination of their treated and untreated drinking water over time. During the final visit in December, researchers again met with families and discussed use habits, attitudes, and behavior and then removed the filters for further analysis.


Overall, the results were very encouraging: participants could assemble the device with minimal assistance or instruction, they liked having the unit in their houses, they used it without any major difficulties, and were able to clean it effectively and use it correctly. All prototypes were still being regularly used after three months.

In several cases, researchers were able to see how water treatment behavior was beginning to shift. Some families reported that they no longer wanted to drink untreated water. They would bring their own water to the neighbor’s house and bottle their children’s water for school.

Although household water treatment products are beginning to penetrate lower-income markets in India, our research confirmed earlier observations that users are highly unfamiliar with water treatment products or practices. This makes it particularly important to design products that are discoverable in their assembly, cleaning, and use; every part must have a clear purpose. PATH worked diligently to design a product that could only be assembled one correct way.

Indian woman takes a sip of water purified by the PATH prototype water filtration device.

Participants were able to assemble the device in under 19 minutes and enjoyed the taste of the water it produced. Photo: PATH/KFlick.

This work paid off, as all households were able to assemble the devices without instruction in less than 19 minutes. We also experimented with a pictorial assembly guide and we think that the first assembly could likely be shortened to 5 minutes or less. The product was by no means perfect, however. Limitations in molding and fabricating the prototype required us to violate design guidelines related to durability of the plastic and ease of cleaning.

The pre-filter displayed some unexpected disadvantages: it caused spilling, and the cloth tore with cleaning and discolored over time. This stymied some users who, unfamiliar with water filters, were not confident that the device could still operate without a pre-filter. This kind of valuable learning would not have been possible without testing the device in the field and observing user behavior over time.

Cross-cultural research

Our learnings extended beyond the device itself and included insights into the process of conducting research across language and cultural boundaries. We found that observations of product assembly were best conducted with a non-Telugu-speaking researcher and a video camera, as this limited the temptation to assist, answer questions, or give nonverbal feedback.

We also learned that nuanced interview questions were so often lost in translation that it was better to focus exclusively on the context behind the research protocol and the rationale for each question first. Only when a common understanding was reached was the research team really equipped to translate and revise the moderator’s guide to the local context.

What’s next?

Now that PATH has seen how our design guidelines hold up in a real-world context, we can speak with confidence with manufacturing partners that want to adopt the technology or adapt their own technology for low-income markets. This is helpful to manufacturers who cannot invest in lengthy and in-depth research for an under-developed market segment. PATH released its design guidelines in April 2011 and will work with manufacturers that want to apply them to their products.

To supplement our deep user-experience research in India, we have also kicked off formative research studies and user needs assessments regarding safe water and sanitation in Africa. Such data helps us identify some of the similarities and differences of users in different cultural contexts, allowing us to develop or refine our design guidelines for manufacturers targeting the African market.

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