Rainwater Calculator

RainCatcher’s Rainwater Harvesting Systems Calculator

This calculator shows you the tank size you will require and the savings you can expect from your rainwater harvesting system.

Part 1: Annual Rainwater Yield

Roof area (m²):
Roof type:

Annual rainfall in your region (mm):

Part 2 - Annual Water Demand

Number of occupants:
Type of building:

Daily Water Consumption per person (Litres):
Additional Daily Water Consumption (other than options below) (Litres):

System implemented for:
Washing Machine:
Garden Use/External Irrigation :

Part 3: Potential Saving

Water supply unit cost (£/m³):

Part 4 - Estimated payback period

Full system (Tank, Pump & Filter) price (£):
Installation Cost (£)

Avg. annual rainfall (mm):
Annual Water Yield (L):
Annual water demand (L):
Annual non-potable water saving (%):
Annual Saving (£):
Minimum rainwater storage (L):
Payback period (years):

This is a guide only based on the simplified approach seen in the QCF BPEC certified course content. Get in touch today to receive a full specification.

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