First Flush Water Diverter

Fitting an appropriately sized first flush water diverter is critical to achieve good quality water. First Flush Water diverters improve water quality and reduce tank maintenance by preventing the ‘first flush’ of water, which may contain roof contaminants, from entering the tank. When it rains, water slowly builds up in the roof guttering system before it exits through the downpipe. The first flush of water from the roof can contain amounts of bacteria from decomposed insects, skinks, bird and animal droppings and concentrated tannic acid. It may also contain sediment, water borne heavy metals and chemical residues, all of which are undesirable elements to have in a water storage system. 

Instead of flowing to the water tank, these pollutants are diverted with the initial flow of water into the chamber of the water diverter. The first flush water diverters from RAIN HARVESTING utilise a dependable ball and seat system - a simple automatic system that does not rely on mechanical parts or manual intervention. As the water level rises in the diverter chamber the ball floats, and once the chamber if full, the ball rests on a seat inside the diverter chamber preventing any further water entering the diverter. The subsequent flow of water is then automatically directed along the pipe system to the tank. A slow release valve ensures the chamber empties itself after rain and resets automatically. The diverted water need not be wasted water because the drain pipe from the diverter chamber can be fitted to a standard drip irrigation system.

Calculating the amount of water to divert
Industry experience and field testing suggests that the amount of water diverted should be determined based on (1) the surface area of the roof, and (2) the amount of pollutants on the roof. The following factors can be used as a guide in determining the volume of water to be diverted.  As a rule of thumb, the more water that is diverted the better the quality of water in the tank. The Diverters are sold in kit form and incorporate standard 90, 100 or 300mm PVC pipes as the diverter chamber section. The length of pipe used will vary depending on the volume to be diverted. Diverters with a variable volume chamber are better than fixed-volume diverters because the volume of diverted water can be customised to the specific requirements of each roof.