Water Tank / JoJo Sizing Calculator for South Africa
Calculate the right water storage tank capacity for municipal backup or rainwater harvesting. Standard JoJo tank sizes, pump notes and installation guidance.
Quick answer: This calculator plans on 150 litres per person per day for full domestic use (our planning default, not an official standard). A 4-person household wanting 3 days of water security during supply interruptions needs 4 × 150L × 3 days = 1,800 litres minimum, making a 2,500-litre JoJo tank the most common household choice.
Water Tank / JoJo Sizing Calculator for South Africa
Full household use: 150 litres per person per day
For planning purposes only. Water tank installations connecting to house plumbing must be done by a registered plumber. Rainwater for drinking must be filtered and treated.
How to Use This Calculator
- Enter occupantsNumber of people relying on the stored water.
- Adjust daily usageDefault is 150L/person/day (our planning default).
- Select days of autonomyHow many days you need if supply is cut.
- Choose intended useFull household, sanitation only, garden or rainwater harvesting.
- Roof catchment area and provinceIf you selected rainwater harvesting, also enter your roof catchment area and select your province for the local rainfall average.
- Click CalculateResults show tank size, number of tanks, pump sizing and days of supply.
Water Storage for South African Households
Water security has become a significant concern for South African property owners. Municipal water supply interruptions (from infrastructure failures, drought restrictions and load shedding affecting pump stations) can leave households without water for days. A properly sized water storage tank provides essential resilience.
We plan on 150 litres per person per day (our planning default, not a DWS standard) for full domestic use including drinking, cooking, bathing, toilets and laundry. For planning a backup tank, this figure combined with your desired days of autonomy gives you the minimum required storage volume.
Standard JoJo Tank Sizes and Dimensions in South Africa
JoJo Tanks is the dominant manufacturer in South Africa. Their tanks are made from LLDPE (food-grade plastic), UV-stabilised and available nationwide. Dimensions below are height × diameter, sourced directly from JoJo's own product specifications. Check diameter against your available stand/plinth footprint before choosing a size, since that's what determines whether a tank physically fits a spot, not just its litre rating.
| Size | Dimensions (H × D) | Best For | Typical Price |
|---|---|---|---|
| 500L | 1,080mm × 840mm | Garden irrigation, small backup | R800–R1,500 |
| 1,000L | 1,300mm × 1,110mm | 1–2 person short-term backup | R1,500–R2,500 |
| 2,500L | 1,860mm × 1,420mm | Most popular residential choice | R3,000–R5,500 |
| 5,000L | 2,255mm × 1,820mm | Family backup 5+ days or rainwater primary | R5,500–R9,000 |
| 10,000L | 3,150mm × 2,200mm | Large property / small farm | R9,000–R16,000 |
| 20,000L | 4,270mm × 2,600mm | Farm, smallholding, commercial | R18,000–R30,000+ |
JoJo has since updated the moulds for its two most popular sizes without changing the footprint: the tank most SA households still call the "2,500 litre" is now manufactured and sold as 2,700 litres, and the "5,000 litre" as 5,250 litres. Both carry the identical dimensions listed above. If a supplier or online listing shows "2,700L" or "5,250L" instead of the round number, it's the same physical tank.
Rainwater Harvesting in South Africa
Rainwater harvesting collects water from roof surfaces during rainfall for storage and later use. The collection formula is: Annual collection (L) = Rainfall (mm) × Roof area (m²) × Runoff coefficient. Typical runoff coefficients: IBR/metal roof: 0.85; clay/concrete tile: 0.80; thatch: 0.60.
| Province | Avg Annual Rainfall | Monthly Average | Dry/Wet Season |
|---|---|---|---|
| KwaZulu-Natal (Durban) | 1,009mm | ~84mm | Summer rain |
| Mpumalanga (Mbombela) | 767mm | ~64mm | Summer rain |
| Gauteng (Johannesburg) | 713mm | ~59mm | Summer rain (Oct–Mar) |
| Eastern Cape (Gqeberha) | 592mm | ~49mm | Year-round |
| Free State (Bloemfontein) | 535mm | ~45mm | Summer rain |
| North West (Mahikeng) | 519mm | ~43mm | Summer rain |
| Western Cape (Cape Town) | 515mm | ~43mm | Winter rain (May–Sep) |
| Limpopo (Polokwane) | 475mm | ~40mm | Summer rain |
| Northern Cape (Upington) | 216mm | ~18mm | Low / semi-arid |
Rainfall is the 1991 to 2020 normal for one representative town per province (Johannesburg, Cape Town, Durban, Gqeberha, Upington, Bloemfontein, Polokwane, Mbombela and Mahikeng), taken from South African Weather Service climate data (read 2026-10-07). Rainfall varies widely inside every province, so check your own area.
Tank Installation Requirements in South Africa
Water tanks connected to household plumbing must be installed by a registered plumber. The connection requires a backflow prevention device (typically a double-check valve) to prevent contaminated tank water from flowing back into the municipal supply. This is a requirement under SANS 10252 and most municipal by-laws. Non-compliance can contaminate the municipal supply and the property owner may be held liable. Do not connect a tank to your plumbing without a registered plumber confirming the correct backflow protection is in place.
Tank positioning affects usable pressure. A tank elevated 1 metre above the outlet produces approximately 10 kPa of static pressure, barely enough for a toilet cistern. For gravity-fed systems to work, the tank must be elevated 3–5 metres above the highest outlet. A pressure pump (R1,500–R4,000) delivers consistent pressure regardless of tank height. This is the more practical solution for most South African residential installations where elevation is constrained by site conditions.
Water Quality and Treatment for Stored Water
Stored water in above-ground tanks is susceptible to algae growth, sediment and bacterial contamination. Food-grade LLDPE tanks such as JoJo's standard range are UV-stabilised and opaque to minimise algae, but unsealed tanks can admit insects and runoff contamination. Always fit a sealed lid, a fine-mesh first-flush diverter on rainwater inlets and an overflow pipe directed away from the foundation. For tanks storing water used for drinking or food preparation, filtration and UV sterilisation are essential. Rainwater is not potable without treatment regardless of how clean the catchment appears. Municipal top-up connections to rainwater tanks must also be managed carefully. A float valve that tops up the tank from the mains supply must be fed through a break tank or air gap to prevent backflow, and the water in a mains-topped tank is no longer classified as municipal supply once it has entered the tank, meaning it must be treated before consumption. SANS 241 sets the national standard for drinking water quality in South Africa. Stored tank water does not meet SANS 241 without treatment unless it comes from a consistently clean municipal source, has been stored for less than 48 hours in a sealed food-grade container and shows no signs of algae or sediment. For longer storage periods or any rainwater use, a basic treatment train of sediment filtration, activated carbon filtration and UV sterilisation is the minimum recommended before consumption. JoJo Tanks recommends draining, scrubbing and sanitising storage tanks with a food-grade chlorine solution every two years, more frequently in warm climates where bacterial growth accelerates.
Frequently Asked Questions
This calculator plans on 150 litres per person per day (our planning default; it is not an official standard). For a 4-person household wanting 3 days of water security during supply interruptions, you need 4 × 150L × 3 days = 1,800 litres minimum. A 2,500-litre JoJo tank is the most common choice for this scenario. For 5 days of autonomy (typical for areas with frequent supply interruptions), a 5,000-litre tank is recommended.
JoJo Tanks (the leading SA brand) are available in these standard sizes: 500L, 1,000L, 2,500L, 5,000L, 10,000L and 20,000L. The most popular residential sizes are 2,500L (municipal backup for small households) and 5,000L (backup for larger families or 5+ days autonomy). For agricultural or large property use, 10,000L and 20,000L tanks are standard. See the dimensions table above for each size's height and diameter.
JoJo tanks are food-grade LLDPE plastic and suitable for drinking water storage when correctly installed with a first-flush diverter (for rainwater) and proper sanitisation. Municipal backup tanks connected to mains water maintain water quality if the tank is cleaned every 6–12 months and UV exposure is minimised (tanks are black to prevent algae). Rainwater collected from roof catchment should be filtered and treated before drinking.
A JoJo tank system for municipal backup requires a transfer pump (typically 0.5–1.5kW), a pressure tank, a pressure switch and a changeover valve. The system switches between mains and tank supply automatically when mains pressure drops. This plumbing work must be done by a registered plumber in South Africa. The system should include a backflow prevention valve to protect the municipal supply from contamination.
The Department of Water and Sanitation sets a minimum basic water supply of 25 litres per person per day (National Norms and Standards for Domestic Water and Sanitation Services, 2017). The typical South African urban household uses roughly 150–200 litres per person per day (our estimate) for full domestic use (drinking, cooking, bathing, laundry, toilets). For garden irrigation, add 2–5 litres per m² of garden per week depending on plant type and season. This calculator uses 150L/person/day as the default for residential backup calculations.
A first-flush diverter automatically discards the first flush of rainwater from your roof after dry weather. This water contains the highest concentration of bird droppings, dust, leaves and pollutants. After the first flush (at least 0.5mm of rain, which is 50 litres per 100m² of roof), the diverter redirects cleaner water to the storage tank. A first-flush diverter is strongly recommended for any rainwater harvesting system and is essential if the water will be used for vegetables, drinking or any sensitive use.
JoJo LLDPE plastic tanks carry a manufacturer's warranty of 8 years and typically last 15–25 years in South African conditions. UV-stabilised black tanks outlast lighter-coloured alternatives because they block light that degrades the plastic. Avoid using the tank as a step or structural support, and do not allow the tank to be completely empty for extended periods. Clean the interior every 12–18 months to prevent sediment build-up and maintain water quality.
Yes, especially with increasing municipal restrictions and unreliable supply in many SA municipalities. A 2,500L JoJo tank costs R4,000–R7,000 installed. With municipal water at R25–R45/kL in most cities, payback is typically 3–6 years at average household usage. Rainwater harvesting further reduces the payback period.
JoJo's standard vertical tank dimensions (height × diameter), from JoJo's own product specifications: 500L is 1,080mm × 840mm; 1,000L is 1,300mm × 1,110mm; 2,500L is 1,860mm × 1,420mm; 5,000L is 2,255mm × 1,820mm; 10,000L is 3,150mm × 2,200mm; 20,000L is 4,270mm × 2,600mm. JoJo has since redesigned the 2,500L and 5,000L moulds to hold slightly more water at no change in footprint, so they're now sold as 2,700L and 5,250L; if you see those figures listed online, it's the same physical tank and dimensions most SA households still call the 2,500 litre or 5,000 litre JoJo.