Rain Harvesting First Flush Diverters 4" WDDP111 White PVC

From the manufacturer: Sold in kit form for easy installation and customisation, our first flush diverters play an essential role in protecting your rainwater quality. By isolating the first flush of contaminant- laden water before it reaches your tank, they keep organic and inorganic fine particles out of the rainwater you harvest so you enjoy the benefits of cleaner rainwater for your property. The following formulas offer general guidelines for calculating how much water you should divert: Areas with low pollution (open fields, no trees, no bird droppings or animal matter, clean environment) = divert 0.0121 gallons of water per square foot of roof Areas with higher pollution (leaves and debris, bird droppings, animal matter/carcasses, pollution) = divert at 0.0242 gallons of water per square foot of roof This calculation will allow you to determine what length and size pipe or pipes you need for your diversion chambers. The length of pipe required to form your first flush diversion chamber will depend upon how much water you need to isolate and capture. The following measurements are given as a guide only. 3 feet of 3? pipe = 1.5 gallons 3 feet of 4? pipe = 2 gallons 3 feet of 12? pipe = 19 gallons