Rainwater Harvesting Guidelines You Should Know

There still are communities around the world that practice rainwater harvesting. Some communities do this as a way of saving water, while other communities do this due to mitigate issues with the water utility provider at times. Still, there are other communities that practice rainwater harvesting as a way of preparing for upcoming dry spells or droughts.

There are two primary methods to harvest rainwater. The first method involves the placement of an empty barrel under a downspout, and the second method involves the construction of a rainwater harvesting system. While both methods work, in that they allow you to take advantage of a clean and safe form of for multiple household uses. Many people choose to use rainwater for all uses in the home, like drinking water, but others choose to use only for select needs, like gardening or washing the car.  For all uses, ensuring that you harvest cleaner, safer rainwater requires that you follow a few key  guidelines.

What You Need to Start with Rainwater Harvesting

  • A drainage and catchment system. This is composed of the roof, gutters, and downpipes that connect tank and roof, among others.
  • A storage tank and its companion accessories.
  • A rain treatment system composed of a number of filters, screens, as well as a first flush device.
  • A pump
  • Fixtures that are connected to the rainwater harvesting system.

General Guidelines for the Installation of the System Components

Drainage and Catchment Parts for Rainwater Harvesting

Many roofing materials are considered to be suitable for the practice of rainwater harvesting, provided that none of the water harvested from these roofs will be used for human or animal consumption. Ensuring that a roof stays suitable for collecting rain involves keeping it clear of debris, plants, and fallen plant and tree parts.

Rain that flows off the roof then goes to downpipes evenly distributed throughout the guttering. Downpipes can be gravity-fed straight to the tank or connected to the underground via a charged drain system. More details on these drain system options are highlighted below.

Gravity system – Comprises at least one tank that is directly fed by downpipes above or near it. Many tanks in a site that are fed by gravity may be connected by underground pipes so that storage in every tank is regulated.

Charged system – Set up so that roof catchment draining is maximised to one tank. Often, pipes remain filled with water between storms unless drained manually. Charged pipes need to be drained to prevent the stagnation of water. Stagnant water causes organic material buildup.

The flow capacity and arrangement of charged drains must be confirmed by either a hydraulic engineer or plumber to prevent gutter overflow during big storms.

Below-Ground Tanks – Need to be sealed in order to prevent groundwater inflow. Also needs to be sited to allow free draining of downpipes to tank. To do this, make sure overflow coming from tank is at least 50mm below inlet above tank.

Choosing Your Storage Tank for Rainwater Catchment

It shouldn’t be hard to select a tank for your residential rainwater harvesting system. After all, tanks are now available in a wide variety of shapes, sizes, and capacities. If you’re looking to save space whilst still enjoying the benefits of clean, safe rainwater, then go for the slimline, underdeck, or underground tank.

Rain Treatment Systems

Rain treatment options come in different variants. You may need many of them to make your rainwater suitable depending on how you’ll be using your water.

Screens for Downpipe and Gutter – A combination of fine and coarse screens positioned at breaks in downpipes (which are located between tank and roof surface) and on at least one section of the gutter can help separate debris from rainwater. They also prevent tank water access by animals like rodents, mosquitoes, and frogs.

Inlet and Tank Screens – To filter water even further, screens need to be set on top of the tank (inlet screens). Finer screens also need to be set over tank outlets to prevent access by mosquitoes. There must also be screens or sun-shades set up to cover every tank inlet so light penetration is minimised, and thus prevent algae growth, which lowers rainwater quality.

First Flush Diverter – The first flush diverter, which needs to be set up after the screening devices on every downpipe and before a tank inlet, keeps out the first flow of water during rainfall, which is filled with contaminants and debris.

Filters – Filters are recommended in situations where water discolouration and pollutants are major concerns. Keep in mind the increased maintenance they need, or else, these may become detrimental, and not helpful, to your system.

Outlet Height – A minimum outlet height measuring 100mm reduces the resuspnsion of sediments trapped at the tank bottom.


A pump is needed to ensure proper distribution of collected rainwater across all sections of your house where water is used the most, so don’t settle for a pump that can’t do just that.


Because rainwater has everything plants need, it’s important that the following maintenance steps be done to your collection system as needed.

  • Regular inspection and cleaning of gutters and roofs.
  • Regular inspection and cleaning of the inlet and outlet screens to prevent the entry of vermin and mosquitoes.
  • The regular checking and cleaning of guards, screens, and first flush diverter.
  • The desludging of the tank once per two or three years.
  • The assessment of a tank’s structure.
  • Check the mains control switch and pump to make sure it works well.
  • Ensure that every leak is fixed so that cyclic starting and stopping does not happen to your pump when a leak occurs.

This post is sponsored by Rainwater Tanks Direct

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