There are a lot of questions people have about water purifiers: Is it good to remove all bacteria? Is it healthy to drink water with no nutritional value? Will a mineral filter truly replace lost minerals? Can purifiers actually make bacteria worse? These are all valid questions — and they deserve real answers.
Debunking Common Water Purification Myths
A simple way to understand the need for purification is to look at the filters themselves. If tap water were truly “clean,” a filter wouldn’t turn brown or become clogged. The visible discolouration on a sediment filter proves that our water contains contaminants — if you filtered bottled mineral water the same way, it wouldn’t turn brown, even with its added minerals.
In fact, some South African product standards require companies to purify municipal water before using it in their end-products. That’s a clear sign that for certain applications, tap water alone isn’t considered clean enough.
It’s also important to understand that all purifiers have a downside if not properly maintained. Never drink water from a purifier if the filters haven’t been replaced on schedule — neglected filters can actually become a breeding ground for bacteria, doing more harm than good.
The Water Purification Spectrum
Water purification is the process of removing undesirable materials, chemicals, and biological contaminants to make water fit for a specific purpose — from safe drinking water to the strict requirements of medical, industrial, and pharmaceutical use.
The process follows a filtration spectrum, moving from large particles down to the smallest dissolved solids:
- Particle Filtration — removes sediment and larger contaminants
- Microfiltration — removes particles up to 0.1 microns
- Ultrafiltration — removes particles up to 0.01 microns
- Nanofiltration — removes particles up to 0.001 microns
- Reverse Osmosis (Hyperfiltration) — removes particles down to 0.0001 microns
Reverse osmosis sits at the very top of that spectrum — it’s the most thorough purification method available.
The Science Behind It: Osmosis vs. Reverse Osmosis
To understand reverse osmosis, it helps to first understand osmosis itself.
Osmosis is a natural process where water moves from an area of low solute concentration to an area of high solute concentration, across a semipermeable membrane — balancing concentration on both sides. The force driving this is called osmotic pressure.
Reverse osmosis inverts this natural process. By applying external pressure greater than the natural osmotic pressure, water is forced from the high-concentration side (where the impurities are) through the membrane to the low-concentration side — separating pure water from its contaminants.
Reverse osmosis was first observed back in 1748, but it only saw large-scale water filtration use centuries later — most notably for desalinating seawater.
How the Membrane Actually Works
At the heart of every RO system is a semipermeable membrane — a layer of material with microscopic pores just 0.0001 microns in size. That’s small enough to block minerals and impurities from passing through.
When pressure is applied, water is forced against the membrane. This pushes pure water molecules through, while contaminants are left behind and flushed out separately as wastewater. The result is water that’s 97–99% pure.
For applications requiring even higher purity — like pharmaceutical production, or cleaning high-voltage power lines — water can be passed through more than one membrane to reach 99.9–100% purity. Since this water has no dissolved minerals, it also has no conductivity, which is exactly why it’s safe for technicians to use on live power lines without risk of electrocution.
Here’s an interesting side effect: because purified water contains no dissolved solids, it doesn’t transfer heat as efficiently as tap water. That makes it excellent for keeping engines and machinery cool — but less efficient for geysers, which end up using more electricity to heat it.
Why Multi-Stage Filtration Matters
In a home RO system, water typically passes through four to seven stages before it reaches your tap.
The first stage is always a particle filter, removing sediment and larger contaminants. Each subsequent pre-filter removes progressively smaller particles, protecting the delicate RO membrane from clogging and extending its lifespan. The specific type and number of filters depends on the quality of your water source.
Keeping these pre-filters clean is essential. A dirty, clogged pre-filter restricts water flow, which can allow bacteria to grow and water quality to worsen — forcing the system to work harder, increasing wastewater output, and potentially letting contaminants slip past the membrane altogether.
Some advanced RO systems include a final mineral filter after the membrane. This reintroduces essential minerals that were removed during filtration, giving the water nutritional value and a more balanced taste — so you get the benefit of both purified and mineralised water from a single tap.
Not sure which purifier is right for your home or business? Read our full buyer’s guide to find the perfect system for your water — or get in touch and our team will help you choose.
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