How to: build your own rainwater harvesting system

How to: build your own rainwater harvesting system

rainwater harvesting system

If you haven’t yet sorted out a water-saving system, now’s the time!

With states of drought declared all over the country, It’s imperative that each province adapts savvy water-saving
methods in the household.

Over and above contributing towards the greater good of the whole country, you’ll save on your water bill and avoid water restriction penalties. It’s also a valuable habit to instil in young children. A major component of domestic water consumption is gardening, estimated to be as much as 31-50% of household water use, but you don’t need to use municipal water for it. This amount can be drastically reduced by implementing rainwater harvesting at home. Because some parts of the country are still lucky enough to experience rain, it’s a good idea to take advantage of this
and harvest the rainwater. It can then be used for irrigation, cleaning the house, washing cars and clothes, as well as topping up the swimming pool.

Did you know?

Rainwater is better than tap water for gardening because it contains no chemicals and has the right pH level.

Advantages of rainwater harvesting

  1. Low-cost solution for saving water.
  2. Low setup costs (depending on requirements and installation), plus easy construction and maintenance.
  3. Easily accessible.
  4. Can work for most households. Although purchasing the components for a home rainwater harvesting system is not cheap (expect to pay between R9 000 and R15 000, depending on the brand), you’ll save a substantial amount of money in the long-term. For a household spending about R800 on a water bill, savings could amount to between R248 and R400 a month.

For example, if you save R300 a month on your water bill: R300 x 12 months (x 5 years) = R18 000 Over a five-year period, you could save R18 000.

3 factors to consider when choosing a tank

 1. Roof size

The larger your roof the more water you can harvest. However, make sure the tank you choose is lower than your roof. For a roof size 50-100m2, a tank ranging from 750-2 200 litres will suffice. For a roof size 200-400m2, a tank ranging from 2 500-10 000 litres should do.

2. Roof type

Metal roofs are the most efficient, followed by tiled. Thatched roofs are not recommended for rainwater harvesting.

3. Space

If space is limited consider a narrower tank, such as a Jojo Slimline Tank.

What you will need

rainwater harvesting system 2

  1. Suitably sized water tank, fitted with an outlet for a tap
  2. Catchment surface (roof)
  3. Gutters
  4. Downpipes
  5. Pre-filtration system (consists of leaf catcher/eater and a PVC first flush diverter pipe)
  6. Tank screen (to keep out insects and smaller debris)
  7. 90˚ PVC elbow pipe (dependent on setup)
  8. Plastic, nickel or solid brass tap
  9. Mounting brackets and nails
  10. PVC glue
  11. Pressure pump and tank connector kit (optional)
  12. Electric drill


Step 1: Placing your tank

  • Place the tank on a smooth and level surface. It should be next to the downpipes you will use.
  • If you don’t have paving, build a concrete platform at least 15cm high and wider in diameter than your
    tank. Make sure the platform is high enough for buckets to fit under the tap. Tank stands can also be purchased.
  • The best area to place your tank is at the lowest part of your roof to allow gravity to guide the rain into the
    gutters and to your tank.

Tip: If you live in an estate remember to ask your body corporate about the tanks they allow as well as the rules regarding tank placement.

Step 2: Connecting the gutters

  • Dry fit before you start, then using PVC glue, connect the leaf catcher on top of the first flush diverter pipe.
  • On the wall where you will mount the first flush diverter, drill two adjacent holes, leaving enough room for the pipe to run through.
  • Using brackets and nails, mount leaf catcher and first flush pipe onto wall below downpipe, leaving a 35mm gap between downpipe and leaf catcher.
  • Using PVC glue, join 90˚ PVC elbow (depending on your setup option) to first flush pipe, so that it can extend into the tank lid.
  • Install tank screen at entrance of tank (some tanks are already fitted; check when you purchase).
  • Install tap at the bottom of your tank. You’ll need a 40/20mm reducer and any 20mm tap.

Pressure pump for irrigation 

Some tank manufacturers offer packages that include a pressure pump as well as fittings that can be installed for added pressure to the system. These packages make it much easier for DIY connecting at home. This will typically be used in situations where you want to use rainwater harvesting with your irrigation system or garden hose. If no pressure pump is installed you will access the water from your tank using a tap.


  • If you want to use the rainwater for drinking, speak to an installer for filtration system options.
  • Remember to enclose the top of your tank to keep debris out and animals safe.
  • Make sure you clean your roof before every rainy season, followed by a monthly checkup to ensure it remains clean, as dust, leaves, animal excrement and dead insects can accumulate on the roof.

Sources: Clearwater Pumps; How to install a Jojo Rainwater System – DIY on BuildersFan YouTube; Installation of a Rain Harvesting System using a JoJo Slimline Tank on Free Rain Conservation YouTube;


Nolwazi Dhlamini

About Nolwazi Dhlamini

Features Writer for Your Family magazine. She’s worked in print and digital media, and finds thrill in understanding human behaviour. Nolwazi believes everyone has a fascinating story to tell, and it just takes the right person, asking the right questions, to find it.


Send this to a friend