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Rainwater harvesting collects precipitation for irrigation, toilet flushing, or emergency use. It reduces groundwater demand and stormwater runoff.
Formel
Calculate: Annual collection = Catchment area × Annual rainfall × Collection efficiency
Trinn-for-trinn guide
- 1Calculate: Annual collection = Catchment area × Annual rainfall × Collection efficiency
- 2Roof collection: 90% efficiency, pavement: 70%, storage needed for dry periods
- 31000 m² roof, 1 m rain: 700-900 m³ water available
Løste eksempler
Inndata
Residential roof 100 m², annual rainfall 500 mm
Resultat
Annual collection ~45 m³ (45,000 L), covers 30-40% irrigation needs
Location dependent
Vanlige feil å unngå
- ✕Under-sizing tank for dry season needs
- ✕Forgetting overflow management (can cause flooding)
Ofte stilte spørsmål
Is rainwater safe to drink?
No without treatment. Suitable for irrigation, toilet, washing after basic filtration.
How large must storage tank be?
Rule of thumb: volume for one dry month. Location's dry season determines sizing.
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