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“Water is the driving force of all nature.” – Leonardo da Vinci
First Flush Diverter
The First flush diverter is a key part of the overall system in my opinion. There are automated first flush diverters or you could do it with a manual downpipe diverter. Clearly the automated version will save you time and water, but since there are only a few available here in England and the price tag is above £70 you may want to dispense with the cost and do it manually. A manual downpipe diverter can be used to create a budget solution, but you will have to manually open up the valve or flap after you feel that the roof has been cleared of dust debris and contaminants. (See downpipe diverters)
The image opposite is of a first flush diverter by Australian company Blue mountain co.
A first flush rainwater diverter is a simple yet effective device designed to improve the quality of harvested rainwater by diverting the initial run off, known as the "first flush," away from the collection system. This innovative tool plays a crucial role in rainwater harvesting systems, especially in areas where water scarcity is a concern. Understanding how a first flush rainwater diverter operates requires a closer look at its design and functionality.
The primary purpose of a first flush diverter is to capture and redirect the first portion of rainfall, which typically carries the most contaminants, debris, and pollutants from various surfaces such as roofs, gutters, and down pipes. These impurities can include bird droppings, dust, leaves, and other particles that may have accumulated on the catchment surface between rain events.
Here in Kent the garden of England, we have had dust storms that we are told originated in the Sahara Desert which have covered cars and building in a red dust. We have also had volcanic dust from Iceland. Between March and June 2010 a series of volcanic events at Eyjafjallajökull in Iceland caused enormous disruption to air travel across Western Europe and left a layer of dust over everything.
There are some who consider a first flush diverter to be a hindrance on the system. As a case in point, all 5 panelists at the American Rainwater Catchment Systems Association's national conference in 2013 agreed that they prefer not to use first flushes.
That being said, I consider this aspect of the system to be of fundamental importance and the information that we have today might of changed the minds of the 5 panelists when they made those assumptions 10 years ago. Apart from the points outlined above about general contaminants, one of my main concerns about the quality of the rain water that I collect, is what elements and compounds are being sprayed from aeroplanes during the “atmospheric aerosol injection” or “chemtrails”.
Whether you believe this to be a conspiracy theory or you have been observing the sky over time and have come to your own conclusions about this peculiarity, there are some wonderful people who have collected samples of dust and water after these events and found very unusual substances within. According to Dane Wingington of, Geoengineeringwatch.org, just to name a few, the following elements have been found in samples. Aluminium, Barium and Strontium.
He is not the only one who has found strange elements that shouldn’t be there is dust and rain water samples, but just to be on the safe side a first flush diverter will prevent that first cover of contaminants to be diverted over from your system.
The basic structure of a first flush diverter
The basic structure of a first flush diverter consists of a pipe or chamber that is connected to the downpipe of the rainwater harvesting system. The diverter includes a mechanism, often a ball or flap, that seals the diversion chamber during dry periods and opens when rainwater starts flowing. When the rain begins, the initial volume of water is directed into the diversion chamber rather than flowing into the main storage tank.
As the diversion chamber fills with water during the first flush, the floating ball or flap rises, sealing off the chamber from the incoming water. This prevents subsequent rainfall from entering the chamber and redirects it into the main storage tank or other designated storage areas. The trapped water in the first flush chamber can then be discharged or flushed away through an overflow pipe.
The size of the first flush chamber is a critical factor in its effectiveness. It must be large enough to capture a sufficient volume of the initial run off, ensuring that the most contaminated water is diverted away. The size of the diverter is often determined based on the surface area of the catchment (roof) with larger catchment areas requiring larger first flush chambers.
Regular maintenance is essential to ensure the proper functioning of a first flush rainwater diverter. Cleaning the diverter periodically, depending on the level of debris and contaminants in the area, helps prevent clogs and blockages. Some diverters also feature removable screens or filters that can be easily cleaned.
In summary, a first flush rainwater diverter operates by capturing and redirecting the initial run off, which tends to carry the highest concentration of contaminants, away from the main storage tank. This helps improve the overall quality of harvested rainwater, making it a valuable tool for sustainable water management in areas facing water scarcity or if you wish to filter the water further for drinking. The design and functionality of the diverter, including the size of the diversion chamber and maintenance requirements, are crucial aspects that contribute to its effectiveness in rainwater harvesting systems.
