The UK has one of the best water systems in the world, with a quality rating of 99.96% according to Discover Water. When you harvest rainwater, you don’t go through the same high quality treatment processes. This means you cannot use the water as drinking water.
However, rainwater is typically softer than treated water. This means that the water quality is more suitable to your appliance, and less likely to cause limescale build up. Furthermore, you can invest in a filtered rainwater harvesting system. These systems gently clean rainwater using natural resources as they store it.