Lagos, Nigeria's largest city, faces significant challenges in providing clean water to its residents, particularly in slum areas where access is often unreliable and contaminated. A mixed-methods approach combining qualitative interviews and quantitative surveys was employed to collect data from 300 youths aged 12-18 years living in four selected slum areas of Lagos. Data collection occurred at baseline (pre-intervention) and follow-up after the installation of eco-friendly water pipelines. The longitudinal study revealed a significant reduction in gastrointestinal disease incidence among participants, with a 40% decrease observed compared to pre-intervention levels. Eco-friendly piped water systems have demonstrated positive health benefits for urban youth in Lagos slums, particularly in reducing the prevalence of gastrointestinal diseases. This intervention can serve as a model for similar urban settings. Local governments and NGOs should prioritise the implementation of eco-friendly water pipelines to improve public health outcomes in underserved areas of Nigeria and beyond. Eco-Friendly Pipelines, Urban Youth Health, Lagos Slums, Gastrointestinal Diseases, Hygiene Practices