When to Upgrade from a Backup Tank to a Borehole

A backup tank gets most Johannesburg households through the odd outage without much drama. Fill it when the pressure is good, draw on it when things go quiet — simple enough. But there comes a point where topping up the tank feels like bailing out a boat rather than solving a problem. That is usually the moment worth pausing to ask whether a borehole belongs in the picture.

This article walks through the practical signs that you have outgrown a tank-only setup, the rough numbers involved, and how the two systems can work in combination rather than in competition.

Why a backup tank is often the right first move

A backup tank-and-pump system is relatively low-cost to install — typically R20,000–R40,000 for a straightforward setup, with whole-house configurations running around R55,000. It requires no drilling, no geological risk, and no borehole pump. You are simply storing municipal water and dispensing it under pressure when the tap runs dry.

For households that experience short, infrequent outages, that is often all they need. The backup water systems category covers the full range of tank options, pump types and sizing guidance if you are still at that stage.

The limitation is obvious: a tank only holds what you put in it. Once it is empty, you are waiting for the municipality just like everyone else.

The signs you are bumping up against those limits

A few patterns suggest you have moved past what a tank alone can reliably handle.

You are draining the tank regularly. If your household is hitting the bottom of a 5,000-litre tank every time there is a multi-day outage, storage alone is not keeping pace with your demand. South Africans use around 237 litres per person per day on average — a family of four can consume close to 1,000 litres in a single day without being particularly wasteful. A bigger tank buys time; a borehole buys supply.

Outages are lasting longer or happening more often. Johannesburg’s reservoir system holds roughly 27 hours of citywide storage buffer under normal conditions. When that buffer is under pressure — through demand spikes, infrastructure failures or the non-revenue water losses that Johannesburg Water has reported at 44.8% in its 2024/25 audited figures — outages can stretch well beyond what most tanks are sized for.

Your water bill is rising steadily. If you are using municipal water for garden irrigation, car washing, or pool top-ups, those volumes add up quickly at the metered rate. A borehole, once the capital cost is recovered, supplies that water at the cost of electricity only.

You are planning a significant property addition. A granny flat, an irrigation system for a large garden, or a small home-based business with meaningful water demand changes the calculus considerably.

What a borehole actually costs

Complete borehole systems in Johannesburg typically run R40,000–R150,000, with most residential projects falling between R60,000 and R100,000. That range reflects genuine variation: depth to the water table, ground conditions, pump specification, filtration requirements and whether you are connecting to an existing tank or plumbing the system from scratch. Borehole pumps alone typically cost R15,000–R35,000 installed.

Those are wide ranges for a reason. A quote from a registered driller who has worked in your suburb will narrow things down considerably — local geology matters more than any national average.

Payback period depends almost entirely on how much municipal water you can displace. For irrigation-heavy properties or households with four or more people, the numbers tend to look more compelling than for a couple in a small townhouse.

How the two systems work together

The most resilient setup most installers recommend is not a borehole instead of a tank — it is a borehole feeding into a tank. The borehole pump runs on a float valve or timer to keep the tank full; your house pump draws from the tank as normal. You get continuous supply even if the borehole pump needs servicing, and you avoid the pressure fluctuations that come from running a borehole pump directly into your plumbing.

This combination also means you are not wholly dependent on either source. If the borehole yield drops in a dry winter (which does happen in parts of Johannesburg), the tank can be topped up from the municipal supply. If the municipal supply fails, the borehole keeps the tank full.

For a detailed side-by-side breakdown of how these two systems compare as standalone options, see the post on borehole vs backup water tank — it covers yield expectations, running costs and practical trade-offs.

If you are seeing the signs above and want to know what a combined system would cost on your property, it pays to get more than one opinion. Compare 3 free quotes — vetted installers, no obligation.

Water quality: what changes when you add a borehole

Municipal water is treated to SANS 241 (2024 edition) standards before it reaches your meter. Borehole water is not treated at source — you are responsible for understanding what is in it and treating it appropriately.

For toilet flushing and garden irrigation, most Johannesburg boreholes are usable without treatment, though it is worth testing before you start. For drinking, cooking or any use where the water contacts food or skin, you need a water quality test first and appropriate filtration or treatment second. This is not a reason to avoid a borehole — it is simply a cost and a step that needs to be in your planning.

Use case	Borehole water typically suitable?
Garden irrigation	Usually yes, test recommended
Toilet flushing	Usually yes
Laundry	Depends on mineral content
Drinking / cooking	Test and treat first
Pool top-up	Test for pH and mineral balance

The decision in plain terms

If your tank empties faster than the municipality can refill it, or if your monthly water bill reflects volumes that a borehole could supply more cheaply, the upgrade case is straightforward. If outages in your area are short and infrequent and your household demand is modest, a well-sized tank may continue to do the job without the capital outlay of a borehole.

The honest middle ground for most Johannesburg households sitting on this decision: get a borehole quote alongside your current tank costs, run the numbers on how much municipal water you would displace, and make the call on payback rather than anxiety.

Knowing whether a borehole stacks up financially on your property starts with a real quote from someone who knows your area. Get your free installer quotes — no commitment, just numbers you can actually use.

A few things to sort out before you drill

Before committing to a borehole, it is worth confirming a handful of practical points. Check whether your municipality requires a registration or licence for borehole use — requirements vary and do change. Confirm the setback distances required from boundaries, septic tanks and structures. Ask the driller about success rates in your specific suburb; yield and depth vary significantly across Johannesburg. And factor in ongoing costs: pump electricity, annual water quality testing, and periodic pump servicing.

None of these are reasons to walk away — they are just the due diligence that separates a system that works well for years from one that causes headaches.