Water · break-even
Rainwater tank or borehole — when does it pay?
Johannesburg’s water went up 12.5% this year, and the top bands cost three times the bottom ones. Pick a rainwater tank or a borehole, put in the quote, and see the year the water you no longer buy covers the cost.
How we calculate it
- The water you replace comes off the top of your bill — municipal tariffs rise in steps, so a saved kL is priced at the band your last kL fall in, not the average.
- A rainwater tank can only replace what your roof catches — roof area x rainfall x the share the tank holds before it overflows. A borehole replaces all of it.
- Year 0 is the install cost, as a minus. Each year saves the kL you no longer buy x the price that year, less the pump’s power and servicing.
- The water price rises by the increase you set. With a loan rate, interest runs while you are still behind.
- Rand as spent, not today’s money; sanitation charged on the water you use, repairs and a new pump are left out.
We calculate; we never name a product, a driller or an installer. Get more than one quote, have borehole water tested before you drink it, and check your municipality’s borehole registration rules.
Where the typical figures come from
- Water prices: Johannesburg Water 2026/27, per kL a month — 0–6 kL free, 6–10 R28.91, 10–15 R29.84, 15–20 R35.65, 20–30 R64.53, 30–40 R69.45, 40–50 R86.81, over 50 R94.92 (12.5% up on 2025/26). Each preset uses the band its saved kL fall in, plus 15% VAT: R33.25 (6–10), R41.00 (15–20), R74.21 (20–30), R89.85 (30–50, the average of two bands). City of Johannesburg, Water Tariffs 2026/27.
- Cape Town 2026/27 (domestic, excl. VAT): R22.10 a kL to 6 kL, R30.37 to 10.5 kL, R47.48 to 35 kL, R95.63 above. Cape Town also charges sanitation on the water you use, so a saved kL is worth more there — add it to the price slider. City of Cape Town, 2026/27 water tariffs.
- Price increases — Low 4.5%, Moderate 9.3%, High 12.5%: Cape Town’s 2026/27 increase on its first two steps, on its third step, and Johannesburg’s increase on every band. Same sources as above.
- Borehole R70 000–R100 000: inside OurPower’s 2026 Johannesburg range of R55 000–R130 000 for a complete domestic borehole (drilling, casing, pump, yield and quality test, electrics). OurPower borehole costs, 2026.
- Rainwater tank R22 000–R48 000: a 2 400 L JoJo tank fully installed (plumbing, electrics, pump, labour) was R20 000 in 2024; a 5 000 L tank alone is about R5 000–R5 500. The Post / IOL, 2024.
- Rainfall 700 mm a year: Johannesburg’s average (South Africa as a whole: about 464 mm). Climate of South Africa.
- Our estimates, not sourced: each household’s monthly use and the kL it would replace, the 5 000–15 000 L tank prices (scaled from the 2 400 L figure), where each borehole sits in its range, the running costs, and the 50% of roof rain a tank catches. Use your own bill and your own quote.