Biotech Rainwater Harvesting Systems


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Rainwater Harvesting

Calculate the correct Storage Tank Volume

The optimum tank size can be calculated by following the 3 easy steps below:

1. Determine local rainwater precipitation volumeRain Water Harvesting Tank Size
Consult the Met Office for Average Rainfall figures for your area. Typically these are about 1,000 l/m2 for UK and Ireland. Then write the average precipitation volume for your area in the box provided below.

2. Calculate the rainwater catchment area of your house
Determine the area of your house roof including all additional projections (independent of the roof slope). If you intend to only use one half of your roof for rainwater collection, then onlyuse this lesser value.

3. Determine the approximate water demand
If you intend to use rainwater for combined domestic and
garden use, you can take the approximate value of ca. 70 litres per person per day when toilets and washing machines are connected. For garden only irrigation purposes, a value of 60 litres per m2 of garden applies. Alternatively use the table below for a more accurate estimate. Now calculate the appropriate storage tank size for your application by following the example below.

Calculation Sheet.
(Please insert your own values in the spaces provided to calculate Yield, Demand, Tank Size and Potential savings)

1. Your annual rainwater yield

Rainwater Harvesting Tank Size Calculation

Rainwater Harvesting Tank Size Calculation