How much can the roof collect?
Estimate event or period yield in metric or US units.
International educational guide
Plan rainwater around rainfall, demand and safe overflow.
Estimate roof yield, compare tank sizes, map non-potable demand and understand the cost, water-quality and code questions that should be resolved before installation.
Choose the question you need to answer
A tank is only one part of the system. Start with supply, demand, overflow or water quality.
How much storage is useful?
Relate demand, dry period and reserve.
Where would the water go?
Build a weekly non-potable demand estimate.
What happens in a storm?
Estimate incoming water and potential overflow.
What is the simple payback?
Compare installed cost, maintenance and water value.
Is rainwater safe to drink?
Understand why potable use needs local health guidance and a validated treatment plan.
Small outdoor project
Rain barrel planning
Start with a stable base, screened inlet, controlled overflow and a realistic garden demand.
Integrated system
Cistern and indoor reuse
Coordinate structure, pumps, treatment, backflow protection, permits and maintenance responsibility.
Drinking-water warning: Rainwater is not necessarily safe to drink. Drinking, cooking, bathing or other high-exposure uses require local public-health advice, appropriate treatment, testing and compliance with applicable rules.