Rooftop rainwater harvesting is the most common type of rainwater harvesting (RWH) for domestic use. It is a simple low-cost technique that requires a minimum of specific expertise and that offers many benefits. Rainwater is collected on the roof and transported to a storage reservoir via gutters, where it supplies water at the point of use. Rainwater harvesting can supplement other water sources when they become scarce or are of low quality like brackish groundwater or polluted surface water in the rainy season. However, rainwater quality may be affected by air pollution, animal or bird droppings, insects, dirt and organic matter. Therefore regular maintenance (cleaning, repairs, etc.) and treatment before water use is very important (e.g. filtration or/and disinfection).