There are 3 main reasons for having a First Flush Tank:
1. If you are building a large Rain Harvesting System with a 3000+ Square Foot Roof.
2. There is a lot of tree coverage hanging over your collection area.
3. If you plan on building a system to bring rainwater indoors for consumption.
If you think about the time that goes by in between rain storms, roofs can get dirty from dust blowing in the wind, various pollen from plants and trees, leafs, sticks, acorns, bird & squirrel droppings, etc. Rain Harvesting First Flush Tanks are installed to wash your roof top by collecting the first bit of dirty water coming off of your roof in your First Flush Tank. Once it’s been filled, the water coming off of your roof will be clean. With proper plumbing, the rainwater will bypass the First Flush Tank and flow into your primary storage tank(s).