‘Ultra Violet Sterilisation is the most environmentally friendly way to treat rainwater and make it fit for drinking.
The Water Supply Regulations 1999 classify rainwater in the same category as raw sewerage. Whilst this may seem unreasonable the rationale is that it may be contaminated with bird and rodent droppings from the collection roof and so may contain harmful bacteria. So for rainwater to be considered fit for drinking in the UK it must be treated.
The simplest and most reliable treatment is to use ultra-violet (UV) sterilisation. In addition the rainwater must be filtered to remove particle of sediment and dirt before entering the UV unit. Once fitted a UV sterilisation systm is safe, efficient and simple to maintain.’