Time between maintenance: filter element replacement
Intervals between replacement of major components (filter element) meet user expectations for device capacity (volume), service life (time), and cost.
Quality and safety of treated water remain within acceptable limits between replacement intervals.
Consumers demonstrate acceptance of the ratio between recurring costs and initial purchase price (by purchasing replacement components at suggested intervals).
Replacement frequency meets consumer expectations for durability and economy (based on analogous products).
Filter element threshold capacity: 2000 L.
Filter element most desirable capacity: 4000 L.
Treated water quality does not exceed safety limits in the intervals between filter element replacement.
Notes and exceptions
Volume-based intervals for better element replacement may be difficult for users to measure in the absence of more explicit indicators.
Low-income consumers will likely expect product components to last several multiples of their advertised capacity or life.
Users may tolerate higher replacement frequencies for very low-cost replaceables such as paper pre-filters or chlorine tabs.
Replacement frequencies should align with cultural norms (holidays, religious events, agricultural cycles, seasons, etc.) that are familiar and easy for users to remember.
PATH. Formative Household Research Point-of-Use Household Water Treatment and Storage Products for Low- and Middle-Income Populations in Andhra Pradesh: Revised Final Report. Seattle, WA: PATH: 2009. Available at: http://www.path.org/publications/detail.php?i=1717.
Reference Design Beta Prototype User Reviews. PATH, unpublished data, 2010.