WaterWater Harvesting

How Does a First Flush System Work?

What is a first flush system? It’s a system where you flush the first dirty rainwater after it rains. This is to eliminate or reduce the contaminants present in your rainwater harvesting system. When you harvest rainwater for future use, you have to make sure that it’s clean enough. If it’s not, the debris and contaminants might clog the pipes and the spouts.

With a first flush system though, you eliminate or reduce the contaminants. There will be fewer worries about the clogs. In addition, your rainwater harvesting system will be much more effective. You can perform irrigation on your garden in a timely manner without relying on your local water supply.

About Rainwater Harvesting

Let’s first discuss rainwater harvesting before we study how first flush systems work. Rainwater harvesting is becoming a popular trend. It makes households somehow self-sufficient. Instead of letting the rainwater run off, they can store that for future use. That’s important especially when it comes to irrigation. The plants and the garden need consistent and continuous supply of water. When it’s summertime and there are a few days when it rains, some of the rainwater must be harvested. This way, you’ll have free water to irrigate your plants even during the dry days.

How Does a First Flush System Work 01

Rainwater harvesting sounds simple. All you need is a collection and storage system where you can gather and store rainwater. However, the collection and storage part are critical. You have to make sure that the water is clean so you can prevent algae growth. Growth of algae and other organisms can clog your spouts and pipes. They can also make the tanks darker and unusable.

The Importance of First Flush System

That’s why we go back to the first flush system mentioned at the beginning. Keep in mind that we’ll be storing rainwater for future use. It could be days or weeks before you can use some of that rainwater for your garden.

Your first flush system will somehow make the rainwater clean for storage. Here’s how it works. Rainwater flows from the roofs and gutters toward the upper end of the downspout. A plastic filter should be there so big junk can get filtered out before they can enter further down into the pipes.

Finally, the 3- or 4-inch pipes lead into a low point where you can turn on and off the flush system. At the start of the rain, the water being gathered is dirty. That’s because the roof and the gutters will be full of dust and other small particles. The inside of the pipes might have also gathered some dirt. Those will go with the “first batch” of rainwater.

If they go straight to the storage tanks, algae growth and accumulation of dirt occur. That will make the tanks discoloured and they might also clog the spouts where water is supposed to come out. That’s why you need to flush the “first batch” of rainwater that comes.

Heavy rain

The total length of the joined pipes (3- or 4-inch diameter each) might be 20 feet or more. It could be much shorter depending on the design of your rainwater harvesting system. After the flushing, clean water can now start coming into your storage tanks. The tanks get filled and you can use the water for future irrigation of your plants.

There you have it. You’ve learned the importance of a first flush system in rainwater harvesting. You’ve also learned how it works. This way, you can install a proper first flush system that helps you collect and store clean water. Your rainwater harvesting system will also work properly because you avoid the accumulation of dirt and clogging of the pipes and spouts in the long run.

A Great Video

Nicholas Burtner and the First Flush

For more from Nicholas, please be sure to check out;

Visit his Website: https://schoolofpermaculture.com/
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The Permaculture Research Insitute

PRI Zaytuna Farm functions as a model farm (in development) and permaculture training facility. Geoff and Nadia Lawton, world-renowned permaculture educators and consultants, lead the project. Much of Geoff and Nadia’s time over the last few years has been spent away from the Institute, consulting and helping set up projects in diverse locales around the world. Seeing the worldwide demand for knowledgeable permaculture consultants and teachers increase exponentially, as fuel and fertiliser prices skyrocket and the effects of climate change, soil depletion and water shortages begin to hit hard, priority and focus is now shifting back to the Institute, where growing the training program will increase the output of quality teachers to help fill the growing need for them.

One Comment

  1. Great explanation of a First Flush System. Important to note, these are not just restricted to small deployments, in larger areas e.g. large carparks etc. where hydrocarbons are present an industrial First FLiush System can also be used to harvest rainwater while reducing contaminants.

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