How to keep your rainwater clean inside your water tank

Is your rainwater clean?

Whether you use your rainwater for irrigation or for domestic purposes, there are a few simple ways to make sure the water inside your rainwater harvesting systems remain as clean and fresh as possible. Click here to see Recommended Rainwater Cleaning Solutions.

1. Make sure your roof and gutters are clean

Make sure your roof and gutters are cleaned regularly from leaves and other debris. Use preventative and non-harmful measures to limit bird and pest droppings and nests under your roof and in your gutters. If you live under trees or in an area with a lot of bird life, consider installing a gutter brush and gutter guards to keep your gutters clean at all times.

You should also ensure your gutters are connected to your downpipes at an angle for the water to flow properly and prevent it from sitting (test by letting the water run from all ends of your gutters).

    2. Install a Leaf Catcher

    A Leaf Catcher, a.k.a Leaf Eater, is a pre-filter that prevents leaves and large debris from entering your rainwater tank. The water from your gutters is directed into the Leaf Catcher before being directed into your water tank with no loss, even during heavy rainfall. If you reside by trees, nesting birds, a dusty or sandy area, then all of the leaves, pieces of nests, deceased geckos, lizards etc, that can get stuck onto the grid are washed out on the side by the current of the water.

    Pro tip: Cut your existing downpipe at an angle so that it directs the water immediately against the grid of the leaf catcher. Be sure to leave a 50mm gap between the downpipe and leaf catcher.

    50mm gap between downpipe and leaf catcher
    Downpipe cut at an angle

            Leaf catcherLeaves and debris in Leaf Catcher

    Dirt and sediments collected in the Leaf Catcher

    Benefits of a Leaf Catcher:

    • A Leaf Catcher is an inexpensive and efficient way to prevent large debris from entering your water tank
    • It is long-lasting and requires little maintenance as it mostly self-cleans (well-made Leaf Catchers also allow you to unclip and clean the grid)
    • By restricting the amount of organic matter getting into your tank, the Leaf Catcher decreases sludge build-up and bacteria contamination

    3. Install a First Flush Diverter

    The First Flush Diverter is positioned between your Leaf Catcher and your water tank. It is used to capture and divert those first few litres of rainwater that wash off from your roof and gutters, and prevent it from entering your water tank. The first few litres of water are often contaminated, by dust (if you reside in a windy area), airborne pollutants (if you reside near an airport or factory), animal fecal matter (mainly from bird droppings) and leaf debris.

    First Flush Diverter
    First flush diverter

    Contaminants are removed at the bottom of the First Flush Diverter (the vertical pipe), while cleaner water enters your tank

    Benefits of a First Flush Diverter:

    By filling up your tank with clean water, the First Flush Diverter will:

    • slow down the growth of algae, harmful bacteria, protozoa and bloodworms
    • limit the build-up of sludge, sediments and contaminants
    • prolong the life of your water pump and filter cartridges used to process your water

    4. Clean you rainwater harvesting tank regularly

    Empty and clean your tank manually (first method, tedious)

    You can empty your tank and use a high-pressure hose to clean the inside, and then let it dry before you connect your tank back to your gutters. However, this method is particularly time-consuming and can be risky as someone is expected to enter the inside of the tank.

    We recommended that you empty and clean your tank at last once every two years.

    Use an automatic tank cleaner (second method, recommended)

    A more efficient and safer way is to install an automatic tank cleaner. A tank cleaner is a system of pipes that siphons the water at the bottom of your tank every time it overflows. It effectively withdraws the water at the bottom 10cm of your tank that contains bacteria, sludge and sediments.

    We recommend that you allow your tank to overflow 3 to 4 times a year when using an automatic tank cleaner.

    How an automatic tank cleaner works

    How an automatic tank cleaner works

    Key benefits of using an automatic tank cleaner vs manual cleaning:

    • Once the tank cleaner is installed, you can set it and forget it, as it is automatic
    • No maintenance is required                                                                 
    • Less water is wasted over time

      Recommended Rainwater Cleaning Solutions

      Leaf Catcher for Rainwater Harvesting
      Leaf Catcher, 80mm for Rainwater Harvesting
      leaf catcher with 80-110mm adaptor

      Leaf Catcher with 80-110mm Adaptor for Rainwater Harvesting

      First Flush Diverter, 80mm
      80mm First Flush Diverter
      First Flush Diverter, 110mm
      110mm First Flush Diverter
      EcoDepot Tank Cleaner System
      Tank Cleaner System

      Is purifying your rainwater recommended? 

      It is highly recommended to install a water system and to ensure that the water entering your tank is as clean as possible to prevent leaves, debris and the harmful growth of unhealthy bacteria. If you intend to use the water in your tank for cleaning, drinking or cooking purposes, the water should be tested (in South Africa: "SANS 241-1:2015 lab test - microbiological and chemistry") and purified through a filtration system that matches the lab test results, making it safe to drink. A standard Big Blue filtration system with a 55W UV sterilizer is the most common purification system used for rain water in South Africa. If any of your rainwater collection systems contain contaminants such as heavy metals or chemical compounds, you might have to invest in a reverse osmosis filtration system.

      Useful links