Rainwater Harvesting Above Ground

The installation of a tank that is filled automatically when it rains. This will require the installation of suitable guttering and piping to transport rainwater to the tank.

The Benefits

It is simply, easy and offers advantages like self-sufficiency and the convenience of not being dependent on regulated water resources.

It presents the opportunity to replace high quality drinking water with rainwater, for low grade uses such as toilet flushing, irrigation, household cleaning and car washing. As a result you will save water, reduce your water bill and have access to an adequate water supply when none is available.


Above Ground Rainwater harvesting component structure

For a basic system you will require:

  1. Tank - Standard tank fittings (intlet/overflow and outlet) are included in the price.
  2. Base / plinth
  3. Pre-filtration
  • Mesh/Tank Screen – beneath tank lid.
  • Rainhead i.e. Leaf Eater
  • First Flush Diverter
  1. Pipes – 3 x 110 mm SV pipes Lengths will vary depending on installation.
  • From bottom of T-junction to slow release control valve.
  • From side of T-junction to elbow.
  • From elbow through lid into tank.
  1. Elbow – 110mm
  2. Tap – 20mm


Note:Purchased separately from dealer and an additional 40/20 reducer is then also required to fit it onto the tank.


How to Maintain Your above Ground Rainwater Harvesting System

  1. Rooftops - Rooftops should be cleaned regularly to avoid contamination of the runoff. During dry weather, dust, leaves, animal excrement and dead insects accumulate on the roof. Make sure that the roof is cleaned before the rainy season starts, followed by a monthly check to keep it clean.
  2. Overhanging Branches - Check that branches overhanging the roof are regularly trimmed back.
  3. Gutters - Ensure that the gutters are free from leaves - consider installing gutter mesh.
  4. Pre-Filtration - Regularly check the pre-filtration device/s to ensure that it is free from leaves and that rainwater can pass through.
  5. Tank Screen- If there is a tank screen below the lid of the tank, clean it if full of debris.
  6. First Flush Diverter - If a first flush diverter is installed, check and clean it out on a monthly basis.

Ensure the diverter is dripping out sufficiently to reset the system.

  1. Keeping your tank Clean - Inspect the inside of the tank every 3 months to make sure that leaf litter has not built up in the bottom of the tank. A properly designed system should not allow leaves and other material to get into the tank.
  2. Water Quality – Please remember that water collected from a roof will not be clean. If the intent is to use the rainwater for drinking purposes, consult an installer with experience in installing water filtration systems. For irrigation purposes however, the water would be perfect.


How to Install Your above Ground Rainwater Harvesting System


Choose a tank

How to calculate what size tank would be sufficient for Rainwater Harvesting:


Roof p/m2

Tank Size

50 – 100

750 L – 2 200 L

200 – 400

2 500 L – 10 000 L

The biggest downfall of Rainwater Harvesting is lack of storage capacity.

Tank placement

Should preferably be at a downpipe, or alternatively be repositioned by use of proper piping/guttering.

Base / foundation

Tanks must be installed on a sound, level and smooth surface. Level paving will suffice, or a properly designed tank stand, alternatively a concrete plinth needs to be built. Ideally the plinth should be covered by a concrete topping at least 85mm thick.

Tank Placement

Should preferably be at a downpipe, or alternatively be repositioned by use of proper piping/guttering.

For installation of your rainwater harvesting system, contact a preferred installer in your area. Installers are listed here.


Recommended base sizes are as follows:



     750 L

     260 mm

1 500 L

1 410 mm

2 200 L

1 420 mm

2 500 L

1 420 mm

5 000 L

1 820 mm

10 000 L

2 200 mm



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