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Rainwater harvesting collects roof runoff for garden irrigation, toilet flushing, and laundry. UK average rainfall of 600-1,200mm annually can supply 30-50% of non-potable water needs.

Formule

Collection potential = Roof area (m2) x Annual rainfall (mm) x Efficiency factor (0.85)

Guide étape par étape

  1. 1Collection potential = Roof area (m2) x Annual rainfall (mm) x Efficiency factor (0.85)
  2. 2UK households use approx 150 litres/person/day; approx 50% is non-potable uses
  3. 3Simple water butts (200L) cost 30-60 GBP and pay back in one gardening season

Exemples résolus

Entrée
80m2 roof, 700mm annual rainfall, 85% efficiency
Résultat
Annual collection: approx 47,600 litres

Questions fréquentes

What is Rainwater Harvest?

Rainwater harvesting collects roof runoff for garden irrigation, toilet flushing, and laundry. UK average rainfall of 600-1,200mm annually can supply 30-50% of non-potable water needs

How accurate is the Rainwater Harvest calculator?

The calculator uses the standard published formula for rainwater harvest. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.

What units does the Rainwater Harvest calculator use?

This calculator works with inches, litres, percentages. You can enter values in the units shown — the calculator handles all conversions internally.

What formula does the Rainwater Harvest calculator use?

The core formula is: Collection potential = Roof area (m2) x Annual rainfall (mm) x Efficiency factor (0.85). Each step in the calculation is shown so you can verify the result manually.

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Paramètres