Blue Mountain WDDP02 First Flush Downpipe

The Blue Mountain WDDP02 100mm First Flush Downpipe is designed to divert and discard the most contaminated water full of hazardous bacteria and fine particles that flow from your roof. By keeping this kind of water out of your tank, you will be able to improve the quality of the rainwater you collect, which is a key step in effective Rain Harvesting practices.

Your first flush diverter can be installed anywhere on walls, posts, stands or even under your eaves that are located between your roof catchment area and your rainwater tank to isolate and capture the first "flush" of dirty water at the beginning of a rain event. You may choose to install smaller diverters to divert rainwater from each downpipe, or you may choose to install larger diverters to divert rainwater from several downpipes.

The more water you divert, the better the quality of the rainwater that ends up in your tank, but be sure to manage exactly how much rainwater is diverted to avoid volume shortages. It's important to calculate your diversion needs and then divert the water accordingly. 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) should divert 0.5 litres of water per square metre of roof; areas with higher pollution (leaves and debris, bird droppings, animal matter/carcasses, pollution) should divert at 2 litres of water per square metre of roof. This should determine what length and size pipe or pipes you need for your diversion chambers.

Blue Mountain WDDP02 First Flush Downpipe Installation Guide