Question 1

Is harvested rainwater safe to use on plants?

Accepted Answer

Rainwater is generally excellent for plants — it is naturally soft, slightly acidic (pH 5.5–6.5), and free of chlorine and fluoride found in tap water. In urban areas, the first-flush from the roof (first 1–2 mm of rain) may carry dust and contaminants, so use a first-flush diverter and discard that initial flow.

Question 2

What is a first-flush diverter and do I need one?

Accepted Answer

A first-flush diverter automatically discards the first portion of roof runoff — typically 10–25 litres — which carries the most dust, bird droppings, and debris. It is highly recommended for drinking water use and good practice for edible crop irrigation. Simple DIY versions cost under ₹500 to build.

Question 3

How large should my rainwater storage tank be?

Accepted Answer

Size your tank to hold at least one month's peak collection to bridge dry spells. For a 50 m² roof in a city with 80 mm monthly rainfall, collection is roughly 3,600 L — so a 3,000–5,000 L tank is appropriate. Bigger tanks also provide buffer during dry months between monsoon cycles.

Rainwater Harvesting

Rainwater Harvesting