Installing a Backup Water Tank: What's Involved

A burst main, a pressure drop, or simply Johannesburg Water’s documented 44.8% non-revenue water loss catching up with your street — there are plenty of reasons to want stored water on your property. But “get a tank” is the easy part. Understanding what the installation actually involves helps you ask the right questions, avoid surprises, and compare installer quotes on equal terms. Here is a plain walkthrough of the process.

Why Johannesburg homes are doing this now

Johannesburg’s reservoir system holds roughly 27 hours of citywide storage buffer. That sounds reasonable until you factor in burst mains, load-shedding-related pump failures, and the city’s own non-revenue water losses. The result is that supply interruptions — sometimes lasting 12 to 48 hours or longer — are a regular reality in many suburbs. A backup tank bridges that gap, giving your household its own small reservoir to draw from when municipal pressure drops or disappears entirely.

If you want a broader look at all your options, the backup water systems pillar covers tanks, boreholes, and JoJo-style solutions side by side.

Step 1 — Choosing where to put the tank

Siting is the first decision and it affects everything downstream. The main factors are:

• Gravity or pump-fed? A tank elevated above your roof can gravity-feed basic fixtures without a pump. In practice, most Johannesburg properties cannot achieve enough height for useful pressure, so a pump is nearly always required.
• Above-ground or underground? Slimline polyethylene tanks (commonly called JoJo tanks after the dominant brand) sit above ground and are easiest to install. Underground tanks need excavation — more cost and disruption, but they stay cooler and are invisible.
• Structural load. A 2,500-litre tank holds roughly 2,500 kg of water. Your slab, paving, or deck must handle that. A good installer will check this before committing to a position.
• Access for maintenance. The pump, inlet valve, and overflow need to be reachable. Cramming a tank into a tight corner saves space but creates problems later.
• Proximity to your main supply line. Longer pipe runs add cost and can reduce flow. Ideally, the tank tees off close to your water meter.

Step 2 — Connecting the tank to your supply

The tank needs a controlled inlet so it fills from the municipal supply when pressure is present, and stops before it overflows. This is handled by a ball float valve — the same principle as a toilet cistern, scaled up. The inlet pipe typically branches off your main supply line before it enters the house.

An overflow pipe must be fitted and directed to a safe discharge point (a garden bed, drain, or soakaway). Without it, a float valve failure floods your property.

A first-flush diverter is not relevant for municipal-fed tanks the way it is for rainwater harvesting, but a sediment screen on the inlet is worth having.

All pipework should use fittings and materials compatible with drinking-water use. South Africa’s drinking-water quality standard is SANS 241 (2024 edition), and any tank or fitting that touches potable water should be rated accordingly. When getting quotes, confirm that the installer specifies SANS 241–compliant components — the SABS (South African Bureau of Standards) certifies products against this standard.

Step 3 — The pump and pressure vessel

Unless your tank is gravity-fed at sufficient height, you need a pressure pump to push water from the tank into your home’s plumbing at usable pressure. A pressure vessel (accumulator tank) works alongside the pump to smooth out pressure fluctuations and reduce the number of pump start cycles, which extends pump life.

Borehole pumps and backup-tank pumps overlap in this space — a good surface pump rated for domestic pressure is typically what gets specified. Pump sizing depends on your household’s simultaneous demand (how many taps and showers might run at once) and the static head (height the pump must push water). An undersized pump gives you a trickle; an oversized one cycles on and off constantly and wears out faster.

As a rough guide, borehole pumps (which share the same product range as backup-tank pressure pumps) typically cost R15,000–R35,000 installed. For a backup tank setup specifically, total system costs — tank, pump, pressure vessel, pipework, and labour — typically fall in the R20,000–R40,000 range, with whole-house configurations around R55,000. Confirm actual pricing via installer quotes for your specific property.

Unsure what a fair price looks like for your suburb and tank size? Compare 3 free quotes — vetted installers, no obligation.

Step 4 — The switchover arrangement

This is the part that catches many homeowners off guard. Simply plumbing a tank into your supply without a proper switchover can mean:

• Municipal water and tank water mixing under certain pressure conditions (a cross-connection that some municipalities prohibit)
• The pump running dry if the tank empties and no one notices
• No easy way to isolate the tank for maintenance

The two common approaches are:

Method	How it works	Typical use case
Manual changeover valve	You turn a valve to switch between municipal supply and tank supply	Smaller budgets; owner is home and aware of outages
Automatic transfer switch / pressure sensor	A pressure sensor detects municipal supply drop and switches to tank automatically	Preferred for most households; works during load shedding or overnight outages

Automatic systems add cost but remove the human-response requirement. If you are regularly away from home or want the system to work without intervention, the automatic route is worth it.

A dry-run protection feature on the pump is also worth specifying — it cuts power to the pump if the tank runs empty, preventing pump burnout.

Step 5 — What happens on installation day

A typical single-tank installation runs one to two days on site for an experienced team. The rough sequence:

1. Mark and confirm the tank position with you present
2. Prepare the base (concrete pad, compacted gravel, or existing slab — depends on tank size and site)
3. Install the tank and connect the inlet float valve
4. Run inlet and overflow pipework
5. Install the pump, pressure vessel, and associated pipework inside the house or in a pump housing
6. Fit the changeover valve and any sensors
7. Connect to the electrical supply (a qualified electrician must do any new DB connections)
8. Test fill, check for leaks, verify pressure at fixtures, test switchover function

More complex installations — larger tanks, underground tanks, long pipe runs, or retrofitting into older plumbing — can take longer. Get a written scope of work before any job starts.

Ready to move from planning to quotes? Get installer quotes for your backup tank — free, no obligation, Johannesburg-based teams only.

What to check before signing off

When the installer hands over the job, run through these basics:

• Tank is full and float valve shuts off cleanly — no drip from the overflow
• Pressure at kitchen tap is acceptable — typically comparable to your pre-installation municipal pressure
• Automatic switchover works — ask the installer to demonstrate by temporarily closing the main supply valve
• Dry-run protection is active — ask how to test it
• All pipework joints are dry — check under visible fittings after the first fill
• You have a written record of the tank capacity, pump model, and pressure vessel size for future maintenance

Also confirm whether your installer has supplied a compliance certificate for any electrical work. In South Africa, new electrical connections require a Certificate of Compliance (CoC) from a registered electrician — it is a legal requirement, not a nice-to-have.

A well-installed backup tank system should need little attention beyond an annual check of the float valve, pump pressure settings, and a tank clean every few years. Getting the installation right the first time is considerably cheaper than fixing shortcuts later.