Downspout First Flush Diverter Kits from Rain Harvesting are simple to install, operate automatically to help prevent pollution of your water tank, and are available in a number of different sizes to suit specific requirements. Simple and effective first flush devices, they are installed at the downspout and used when there are a small number of downspouts supplying water to the water tank/cistern. It is preferable to fit the longest length chamber as possible to ensure better quality water. Install from the roof gutter and after the rain head, to within 6" above the ground to allow easy access to the end cap.