The FILTER efficiency of the FARMLAND RAINY RWH FILTERS is more than 90%

An example : The total roof top area available for rain water harvesting at Urban/ Rural Area is 30 x40 = (110 m2)

A tiled/RCC roof an area of 110 m2, Using a Rainy RWH Filter in an area with local annual rainfall of 800mm would yield:-110 x 0.85 x 0.90x 800 =(67000liters) (67 m3)

To calculate the required tank size:

A proven and workable rule-of-thumb in size of the tank to store rainwater has to be 5% of the annual rainwater yield. This has been shown to give a reliable optimum tank size. For our example therefore, the storage tank required would be: 5% 0f 67000=3400 (3.4 m3)

It is advisable to go for 4.5 M3 (4500 liters) Reinforced Cement Tank or existing tank can be used for collection of water and over flow can be connected to the bore well for re-charging the well.

Incase maximum rainfall per day is 50 mm/hr the rate of the flow of water will be 70 LPM at 85% /0.90% efficiency of Filter and Tiled Roof, so that you will get 4200 liters of water. Hence 4.5 M3 tank will be sufficient since the water can be used every day and thus the tank will be ready for holding the water of the next rains. Tank size may also be calculated on the required usage of rainwater.

WATER SAVING CALCULATION: The consumption of water per person in urban India is considered 130 liters per day. For a household of FOUR peoples the average annual demand will be: 130 x 4 x 365 = 189800 liters. The Rainwater Harvesting System (110 m2 Roof Area x 800 mm rainfall/ year using Rainy-FL150 RWH FILTER) supplies 67,000 liters. Considering every day consumption 520 liters, the harvested water will be sufficient for 130 days, an annual saving of 35% of the total annual requirement.