Accessing clean water and sanitation is a constant challenge for urban residents in informal settlements and marginal areas. For most residents, informal local water and sanitation service providers meet these basic needs. These local entrepreneurs or enterprises provide services paid for directly by the clients. They are not planned, authorized, supervised, or acknowledged by the formal authorities as part of the official system. These services include water tankers, bottled water delivery, provision and management of shared or community latrines, unregistered pit emptying, container-based sanitation, or piped water to a private household or shared tap. These informal service providers, or intermediaries, have emerged in response to a significant essential service gap. Since the unstructured nature of water provision in Nairobi County is a major problem that needs to be addressed, this study evaluated the structure of the system of water service provision that is in existence in Nairobi County. The study utilized descriptive research design. The research was informed by the systems theory. Target population for the study consisted of households from the informal settlements and other water related stakeholders. Data was collected from a sample of 388 households from nine slums in 12 sub-counties derived through simple random sampling. Household questionnaires were used to collect data. The data was analyzed through descriptive and inferential statistics. Findings from this study indicated that 51.0% of the respondents had no water service structure, 8.7% had basic structure, 2.9% had intermediate structure, and 37.5% of the respondents had full water service structure. It was also established that, water structure had a significant relationship with availability, access and quality. Examined, against sub-counties, there was a significant influence between water structure and the sub-counties. Based on the findings, the study concludes that, provision of infrastructure alone may not lead to household water security and recommends that while planning the development of a water supply system structures (production, treatment, storage and distribution), the decision should be based on whether the investment will improve availability, access, quantity, quality, affordability and reliability of service. Accordingly, this decision should help inform the investment by policy makers to ensure water security.
