Do First Flush Diverters Remove Heavy Metals From Rainwater?

What First Flush Diverters Do

First Flush Diverters (FFDs) are devices installed at the roof gutter outlet to redirect the initial flow of rainwater, known as the first flush, away from the storage tank. This initial flow can contain high concentrations of debris, sediment, and contaminants that may have accumulated on the roof surface. By diverting this water, FFDs help to minimize the risk of contamination in the stored rainwater.

Effectiveness of First Flush Diverters

A typical First Flush Diverter is designed to divert the first 10-20 gallons of rainwater, depending on the device and the roof size. This initial diversion can range from 5-50% of the total roof area, and the actual amount diverted depends on the roof’s surface area and the gutter system’s capacity. For example, a small roof with a 1000 square foot surface area might divert 1-2 gallons per inch of rainfall, while a larger roof with a 10,000 square foot surface area might divert 10-20 gallons per inch of rainfall.

Heavy Metal Removal

While First Flush Diverters are effective in removing debris and contaminants from the initial rainwater flow, they do not remove heavy metals. Heavy metals, such as lead, copper, and zinc, can leach into the rainwater from the roof’s surface, the gutters, and other materials, and can persist even after the first flush has been diverted. To remove heavy metals from rainwater, additional treatment steps, such as filtration or chemical treatment, may be necessary.