The answer is No… but why is that?
Collecting rainwater is not regulated in the slightest but what you do with it afterwards most certainly is if you intend to pipe it into a building or make it available for public consumption.
The critical aspect is that it must be clearly labelled as non-potable and must never, ever be allowed to backflow into the public mains water system to safeguard drinking water supplies.
Characteristics Of Rainwater vs Public Mains Drinking Water
Rainwater is essentially untreated water. That means it almost certainly contains contaminants or microbial agents, and possibly pathogens. Even rain that falls straight from the clouds will more than likely pick up particles of dust or fungus that float in the atmosphere. As rainwater harvesting usually collects water from rooftop surface areas, it is typically contaminated with bird and rodent droppings as well as dirt and dust blown by the wind. In short, it is not clean water and far from drinking water quality. It can easily be filtered to remove most physical impurities but would need to be treated in some way; e.g. ultraviolet light, or chlorination to destroy bacteria and pathogens.
What Are The Recommended Or Permitted Uses For Harvested Rainwater?
It may safely be used for purposes where there is no risk of contaminants endangering public health. That includes applications such as vehicle washing, toilet flushing (27% of domestic water consumption is flushed down the toilet), gardening and irrigation, washing machines and general outdoor washing such as cleaning pathways. Rainwater is also widely used in farming. However, it is not suitable for dishwashers, showers or bathing unless treated.