Assess learners' ability to design a household rainwater harvesting system by (1) calculating required storage from catchment area, local rainfall patterns, and household demand; (2) sizing and explaining a first‑flush diverter (volume and divert timing) to protect storage quality; and (3) selecting appropriate pre‑filtration and treatment options for specified end uses (irrigation, nonpotable indoor use, or potable) with justification of tradeoffs, maintenance needs, costs, and code considerations. Provide one worked calculation, a brief component layout/schematic, and a short justification for chosen filtration and first‑flush design.