Check the intended rainwater use and local requirements, model one rain event with tank limits, and plan installation, overflow and maintenance records.
Start with a specific low-ingestion use such as watering ornamental plants, then check local health, water and building requirements. Record who will use the water and how access is controlled. For edible plants or other uses with ingestion exposure, obtain appropriate local guidance before designing the system.
Identify the horizontal roof area actually routed to one tank and the rainfall depth for an observed or clearly labeled assumed event. Record the runoff percentage and first-flush diversion source. Use either metric or US units consistently and note water already stored.
Enter the event data, usable tank capacity and initial stored water. Inspect theoretical runoff, diversion, retained inflow and overflow. Test a nearly full tank and a dry event to see the limits. The model assumes no drawdown during the event.
Use the manufacturer’s requirements and local design advice for filled-tank support, secured access, screening, overflow routing and maintenance access. Keep nonpotable collection separate from drinking-water plumbing. Include these parts and any required professional work in the installation plan.
After installation, check the system during a suitable event and record starting level, diversion behavior, overflow route and final level. Maintain screens, gutters and other parts as directed. Record uses, water-quality concerns and repairs, and reassess the plan before changing to a higher-exposure use.
Keep the intended use, local source links, permissions and unanswered water-quality questions. · Record the measurement method, rain-event source and diversion assumptions. · Keep the approved installation scope and acceptance checklist with the system instructions. · Save event observations, maintenance dates and the next inspection action.
Calculate one event’s retained inflow and overflow after documented runoff losses, first flush and available tank capacity.
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CDC describes microbial and chemical risks in collected rainwater and recommends safer sources for ingestion-related uses, including edible plants. Ask the local health authority about testing, treatment and intended use.
Gross volume is horizontal catchment area × rainfall depth. Routed inflow less diversion is capped by free storage. The output reports overflow and assumes no water use during that event.
Keep nonpotable plumbing separate and control access and mosquito entry. Follow applicable local requirements and the system’s maintenance instructions.
A dated rain measurement and starting tank level make the model easier to compare with actual operation.
Tank price alone omits support, screening, diversion, overflow and access work.