Constant-Pressure vs Standard Borehole Pumps

Choosing between a constant-pressure and a standard borehole pump is one of the more consequential decisions in any borehole installation. Get it wrong and you either overspend on technology you don’t need, or you end up with frustrating pressure drops every time two showers run at once. Here is a plain comparison to help you decide.

How each system actually works

A standard (fixed-speed) pump has one gear: on or off. When the pressure in your system drops below a set point, the pump kicks on at full power and fills a pressure tank — typically a small vessel with an air bladder — until the pressure reaches its upper limit, then it switches off. Pressure at your taps is reasonable when the tank is full, but it fluctuates as the tank empties between pump cycles.

A constant-pressure pump (sometimes called a variable-speed or inverter-driven pump) pairs the pump motor with a variable-frequency drive (VFD). Instead of cycling on and off, the drive continuously adjusts the motor’s speed to match actual water demand at that moment. Open a second tap and the pump speeds up; close it and the pump slows down. The result is pressure that stays within a narrow band — typically within a few kilopascals of your target — regardless of how many outlets are open.

Pressure consistency in practice

For a single-person flat or a weekend cottage with light, sequential water use, the difference between the two systems is barely noticeable. For a family home where someone is showering, the dishwasher is running, and someone else is filling a kettle simultaneously, it is very noticeable. Standard pumps struggle to keep up with simultaneous demand; the pressure tank runs low faster than the pump can refill it, and you feel the drop at the shower head.

Constant-pressure systems handle simultaneous demand more gracefully because the pump’s output is always matched to what is being drawn. This is particularly relevant in Johannesburg, where borehole drilling is increasingly the backbone of household water supply rather than a backup, meaning the pump needs to perform like a utility, not an occasional supplement.

Cost differences

As a rough guide, a standard fixed-speed submersible pump installed in Johannesburg typically sits in the lower portion of the R15,000–R35,000 installed range for borehole pumps. A constant-pressure system — pump, VFD controller, pressure sensor, and associated wiring — will typically add R8,000–R20,000 to that figure, though you should confirm exact numbers with installers via quotes, because controller specifications and borehole depth affect the total considerably.

For context on wider system costs, our guide on submersible borehole pump costs walks through what drives the price differences between pump specifications. The full borehole system, including casing, pump, pipework, and a pressure system, typically runs R60,000–R100,000 for most Johannesburg residential installations, with the overall range sitting at R40,000–R150,000 depending on depth and equipment choices.

Energy consumption

This is where standard-pump advocates have a point. A fixed-speed pump running at full power for short, sharp cycles can be efficient when demand is moderate and predictable. A variable-speed drive adds a small amount of baseline electrical draw from the controller itself.

That said, a constant-pressure pump running at reduced speed during low-demand periods uses less electricity than a fixed-speed pump cycling on and off repeatedly. The real-world efficiency difference depends heavily on your household’s water usage pattern. As a rough guide, homes with highly variable demand across the day tend to see modest energy savings with constant-pressure systems; homes with very consistent, low demand may see little difference. Ask installers to show you the motor efficiency curve at partial load for the specific unit they are quoting.

Not sure which pump type suits your borehole depth and household size? Compare 3 free quotes — vetted installers, no obligation.

Maintenance and failure considerations

A standard pump’s simplicity is a genuine advantage. Fewer electronic components mean fewer things that can fail, and a local pump technician can diagnose and repair most faults without specialist equipment. Pressure tanks can waterlog over time (the bladder fails), but they are straightforward to replace.

Constant-pressure systems introduce a VFD controller into the chain. These are reliable under normal conditions but are sensitive to power quality — voltage spikes, sustained undervoltage, and dirty generator power can damage the drive. Given Johannesburg’s ongoing load-shedding environment and the prevalence of borehole systems running off generators or solar inverters, the power supply feeding your pump controller matters. A proper surge-protection device and a clean, stable power source are not optional extras with a VFD system.

Our overview of choosing the right borehole pump size covers how flow rate and head requirements interact with pump selection — worth reading before you finalise any specification.

Which type suits your situation

Use this as a rough decision guide:

Situation	Likely better fit
Single household member, light use	Standard fixed-speed
Family home, multiple simultaneous outlets	Constant-pressure
Budget is the primary constraint	Standard fixed-speed
Borehole is primary (not backup) water source	Constant-pressure
Unreliable power supply, limited surge protection	Standard fixed-speed
Clean solar or inverter supply with stable output	Either — constant-pressure viable
Existing system upgrade, same borehole	Check yield and pipe size before upgrading

The table above is a starting point, not a rule. A borehole with a low yield (slow recharge rate) may not benefit from a constant-pressure pump at all — the pump will simply run at reduced speed most of the time regardless. Yield testing before specifying your pump is essential, and any credible installer should insist on it.

Ready to get specific costs for your property and borehole depth? Request your free installer quotes — no commitment, three independent prices.

Making the final call

Constant-pressure pumps are not universally superior — they are the right tool for households with variable, simultaneous demand and a reasonably clean power supply. Standard pumps are simpler, cheaper, and easier to service, and they do the job reliably for lower-demand applications.

Before committing to either, have an installer assess your borehole yield, your household’s peak demand, and the quality of your electrical supply. Those three factors, more than any general comparison, will determine which system gives you the best return. Drinking-water quality from the borehole is a separate consideration governed by SANS 241 (2024 edition) — treatment requirements can affect system design too, so factor that into your planning from the start.