Treatment of rainwater ensures that the water will be safe to use. This section is divided into three sections to better help you understand the treatment of rainwater. The first section, Roofwater Quality, discusses potential contaminants in rainwater, which explains what we are trying to treat for. The second sections discusses pre-storage treatment, which makes the water cleaner before it enters the storage tank. The final sections will discuss after-storage treatment, which filters and disinfects the water so that it can be used safely.