The rule stipulates that rainwater must remain completely separate from the public water supply. For amateur gardeners, this means: anyone who does not adapt their collection system runs the risk of being punished for mixing it with drinking water. The relaxing hours in the green could quickly take on an unpleasant aftertaste.
Rainwater is free and often less contaminated than tap water. Many plants, especially those sensitive to lime, thrive better with it. That's why numerous garden owners rely on their own collection and use to save money and protect the environment.