What Is The First Flush, And Why Does It Matter?
When the skies finally open over a dry Australian suburb, it’s more than just a welcome downpour - it’s a rush of water over roads, roofs, and gutters, carrying with it weeks of dust, debris, bird droppings, and potentially even chemicals. You may have never thought about that first burst of rain, known as the first flush, but it can be impacting your water quality.
What is the First Flush?
The term first flush refers to the initial flow of rainwater during a rainfall event. In dry climates like ours, surfaces accumulate a layer of pollutants between rain events. When the rain finally arrives, that first flow picks up most of the accumulated grime and washes it into storm drains—or, if you’re collecting water, it washes into your rainwater tank.
You can capture and divert this polluted water by using a first-flush diverter to ensure that only quality rainwater makes its way into your tank.
How First Flush Diverters Work
As rain begins to fall, the first flush diverter collects the first portion of water - you decide based on your roof area and your environment how much water you want or need to divert.
In a traditional first-flush diverter that utilises a storage chamber, the first flush of water is stored in the chamber. There is a ball inside the chamber that, as the water level rises, floats to the top of the chamber. When the first flush of water has filled the chamber, the ball seals it off, and high-quality water flows into your tank.
There are large first flush diverters for properties that need to divert a lot of water, and there are first flush diverters that can be installed in-ground.
Rain Harvesting™ also offer chamberless first flush diverters for properties that might be short on space.
Meet the First Flush Carrot. This little powerhouse diverts the initial 20 litres of roof run-off without the need for a traditional storage chamber. You can learn more about the First Flush Carrot here.
💡Stratco Tip: There are first flush options that come with built-in leaf diversion, like the Total Rain. Consider if a combination first flush and a rain head is right for your home.
Take the First Step Toward Cleaner Rainwater
First flush systems offer a low-tech but high-impact solution that fits every home! Ready to upgrade your rain harvesting system?
Explore Rain Harvesting™’s First Flush Diverters—available now through Stratco.
Our team is here to help you design a smarter, cleaner water collection setup for your home.