How Should I be Filtering My Harvested Rainwater?

How Should I be Filtering My Harvested Rainwater?

Collecting rainwater is a fabulous way to save a wide variety of household water expenses; from flushing toilets to washing cars to irrigating lawns, putting the rainwater you collect to use is great for both the environment and your wallet!

But collecting water for drinking is a little bit different - naturally, there are considerations to be made when you plan on using the collected water for drinking or cooking.

Before you select filter methods and other add-ons, make sure you have a plastic collection tank that is intended specifically for potable water. These tanks will be black or dark green in colour to avoid excess sunlight penetration and keep algae growth inside the tank at bay.

The next step you'll want to take is assessing what measures you have available for filtering the water before it enters the tank. The better this water is filtered, the more sanitary it will be before the final filtering process. You should have a minimum of two points of filtration between the roof and the collection tank, but 3-4 methods is preferable. Filtration will also depend on how you'll be using the water; garden use will require less filtration and potable use will require more.

Step 1: gutter covers

The first point of filtration should be where the rain enters the gutter from the roof; a fine mesh filter screen fitted to the top of the gutter is best. This filtration is intended to block out heavy leaves, sticks, shingle grit, and other large and easily diverted debris. This will eliminate the need to clean gutters and get cleaner water into your tank.

Step 2: rain head

The second point of filtration is a rain head fitted to the downspout past the point where the water has passed through the gutter mesh.

This second filter is a rain head with a sloped screen and a much finer grated liner; this is intended to keep out insects and other pests and to catch anything that may have fallen through the first filter.

Step 3: first flush diverter

The third point of filtration is a first flush diverter located between the downspout and the collection tank.

The water should flow through this diverter to avoid sediment buildup and other contaminants from entering the tank - this means cleaner water entering your reservoir and it's once again filtered to remove debris.

Step 4: calming inlet

The fourth thing you'll want to keep in mind is that you need to avoid disturbing the sediment that settles at the bottom of the tank by installing a calming inlet; you'll want to draw water from the middle of the tank where it's the cleanest. Pumps with floating suctions enable this process.

Once you've set up a number of filtration methods to clean the water before it hits your tank, now you can sit back, relax, and let your reservoir fill with rainwater.


Your final step in turning rainwater into drinking water is to find a filtration method that will safely remove bacteria, chlorine, and any leftover debris such as sediment. This will require a more advanced method, such as a chemical treatment or a commercial water filter before actually consuming the water.

For more information or to get started on designing a rainwater collection system, contact us today! Our team is highly experienced in designing both residential and commercial rainwater harvesting systems; we’ll help you select the right products and put together a system that works for your property and make sure you have an ample capacity reservoir to meet all your household needs.

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