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Rainwater Harvesting Tanks Guide

A Comprehensive Guide for RotoTank™

Rainwater Harvesting Systems

Rainwater harvesting is a sustainable and environmentally friendly way to collect and store rainwater for various uses. One of the key components of a rainwater harvesting system is the rainwater harvesting tank. Our Rainwater Harvesting Tanks Guide explores the world of rainwater harvesting tanks and answers some common questions.

  • Including how to determine the size of the tank you need.
  • The legality of rainwater harvesting in South Africa
  • And the best types of tanks for rainwater collection.
rototank, rainwater harvesting tank

How Big of a Tank Do I Need for Rainwater Harvesting?

Determining the size of the rainwater harvesting tank you need depends on several factors.

  • Your location
  • Average annual rainfall
  • Your water usage
  • And the intended purpose of the harvested rainwater.

Our Rainwater Harvesting Tanks Guide helps you calculate the tank size:

a) Calculate Your Water Needs: Start by estimating your water consumption for different purposes. A typical example is for, irrigation, toilet flushing, and outdoor usage. This will give you an idea of your water needs.
b) Measure Your Roof Area: Measure the roof area that will be used for rainwater collection. Multiply the roof area (in square meters) by the annual rainfall (in millimetres) to calculate the potential volume of rainwater.
c) Adjust for Efficiency: Keep in mind that not all the rain that falls on your roof can be collected efficiently. Typically, you can collect around 80-90% of the rainwater that hits your roof.
d) Calculate Tank Size: Divide your estimated water needs by the efficiency-adjusted potential rainwater volume to determine the tank size required. Remember to round up to ensure you have enough capacity.

At RotoTank™ we work on a general guideline of a family of four requiring a 5000l rainwater harvesting tank. A smaller household with two people would find our 2500l or 2200l ample. This depends on the ground area you have available on your property. Tanks should be closest to your downpipes to set up your rainwater harvesting system.

Our vertical 5000l rainwater harvesting tank has a diameter of 1800mm. The diameter of a vertical 2500l rainwater harvesting tank is 1400mm. With various other options available for confined spaces, we advise our clients to measure the area. We can assist with the tank that will give them maximum collection to utilise the space they have available.

Is Collecting Rainwater Harvesting Illegal in South Africa?

In South Africa, rainwater harvesting is generally legal and encouraged. This practice helps conserve water resources, especially in regions prone to drought. There are regulations and guidelines in place to ensure responsible rainwater harvesting practices.

Here are a few key points to consider:
a) Permit Requirements: In some municipalities, you may need to obtain a permit for rainwater harvesting. Particularly if you plan to use the harvested rainwater for potable (drinking) purposes. Check with your local municipality for specific requirements.
b) Water Quality: Ensure that your rainwater harvesting system meets water quality standards. Especially if you intend to use the collected rainwater for drinking or cooking. We will always encourage filtration on a rainwater system. Researchers at RotoTank™ have investigated the best solutions. We supply all the filter units required via our turnkey solutions and Combo units.
c) Sustainable Practices: Follow sustainable and responsible rainwater harvesting practices. Such as using appropriate filtration systems and maintaining your tank and gutters to prevent contamination.

At RotoTank™, we recommend you consult your local authorities or body corporates. Adhere to local regulations when setting up a rainwater harvesting system in South Africa. The correct installation is essential, especially your runoff, in situations when the tank overflows with heavy rains. Your overflow must not impact a neighbour’s property, by undermining walls or natural run offs.

What are RotoTank Rainwater Harvesting Tanks?

A rainwater harvesting tank is a storage container designed to collect and store rainwater from rooftops or other surfaces. These tanks come in various sizes, materials, and designs to suit different needs and preferences. Here are some common types of rainwater harvesting tanks:

a) Polyethylene Tanks – RotoTanks: These are by far the most cost-effective and lightweight, making them easy to install and maintain. Our Tanks are available in various sizes and are suitable for above ground and underground installation. RotoTank™ rainwater tanks are manufactured with only the highest standard of polyethylene pellets. Produced with a protective black inner liner to guard against the high UV radiation, that cause bacteria and algae.
b) Concrete Tanks: Concrete tanks are often buried underground. They can store large volumes of rainwater, they are vulnerable to tree roots. It is difficult to see the volume in the underground tanks. Tanks require submersible pumps to get the water out.
c) Metal Tanks: Metal tanks are known for their strength and durability. They are often used for industrial and commercial rainwater harvesting systems. They are extremely expensive and are susceptible to rust and corrosion.
d) Fiberglass Tanks: Fiberglass tanks are corrosion-resistant and lightweight. They are a suitable choice for above-ground installations only. Unfortunately, they are brittle and do not have a long lifespan. Fiberglass Tanks do not have a liner to protect against the harsh weather fluctuations, resulting in higher pollutants.
e) Bladder Tanks: These flexible, collapsible tanks are ideal for limited space and can be placed in crawl spaces or basements. The major flaw with bladder tanks is punctures, that can result in flooding your home.

What is the Best Tank for Rainwater Harvesting?

RotoTank™ has the best range of rainwater harvesting tanks, depending on your specific requirements, budget, and available space. Here are some considerations to help you make an informed decision:

a) Tank Material: Consider the material’s durability, cost, and suitability for your climate.

For example, polyethylene tanks are excellent for all climates, especially during South African summers with high humidity. Typically our tanks do extremely well with frost, the tanks have a stretch and give, that acclimates to the weather conditions.
b) Tank Size: Choose a tank size that aligns with your water needs, available space, and budget. Remember to factor in the efficiency of your rainwater harvesting system.
c) Water Quality: If you plan to use harvested rainwater for drinking or cooking, invest in a tank and filtration system that meet water quality standards. A full range of these items is available online or instore at all RotoTank™ Branches.
d) Installation Location: Determine whether you want an above ground or underground tank, depending on your space and aesthetic preferences. RotoTank™ has both options in various sizes.
e) Maintenance: Consider the ease of tank maintenance, including cleaning and repairs. Regular maintenance is always recommended. Water purification tablets are an added essential to your system for more information on the correct dose for your tanks. Refer to our RotoTank™ online shop platform.


In conclusion, there are several reasons to choose a RotoTank™ Rainwater Harvesting System.

Rainwater harvesting is an eco-friendly and sustainable practice that can help you reduce your reliance on traditional water sources. Make the most of a RotoTank™ rainwater harvesting system. Use our rainwater harvesting tanks guide for assistance in choosing the right rainwater harvesting tank. It is essential to ensure the correct size for your needs while also ensuring compliance with local regulations.

In South Africa, for the best quality and durable rainwater harvesting tanks choose RotoTank™. The brand that stands out from the alternatives. Our ten-year warranty and all the fixtures, filters and pumps required to set up your system. RotoTank™ offers a unique shopping experience with turnkey solutions that get delivered free to your door.

RotoTank™ Rainwater Harvesting Tanks Guide you can harness the power of rainwater to benefit your household and environment without shocking your pocket.

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Read More about Installing Rainwater Harvesting
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