Clean drinking water matters. Tap water is treated, yet it may still pick up chlorine, metals from plumbing, and fine particles on the way to your glass. This blog explains how water filtration works, what filters remove, and which filtration systems are available. You will also see how independent certification helps you compare products with clear facts.
What is a water filter?
Water filters are devices that physically or chemically remove impurities from drinking water. Most home systems combine stages so they can catch particles, improve taste and odour, and reduce selected dissolved contaminants. The key point is simple. Different technologies remove different things, so start by matching the filtration method to your needs.
Key components you will often see
- Mechanical filtration (sediment pre-filter) that strains grit, rust and sand to protect finer stages.
- Activated carbon to adsorb chlorine or chloramine and many organic chemicals that affect taste and smell.
- Reverse osmosis (RO) membrane to reduce dissolved contaminants that carbon alone cannot address.
- Post-filters to polish taste before the water reaches your glass.
Water filters are increasingly used to reduce specific contaminants, improve flavour, and cut plastic waste from bottled water. Choosing a system with independently certified performance helps ensure results.
AquaTru is tested to remove up to 99% of all harmful substances in your water. It comes in plug-and-play countertop options (Classic and Carafe) and an Under Sink system.
What does a water filter do?
A water filter removes contaminants from tap water. Its purpose is to make water safer to drink, better tasting, and clearer.
- Support health and wellbeing. By lowering exposure to unwanted chemicals and metals, a suitable, independently certified filter helps reduce everyday intake of substances that can affect health over time. Always check claims against recognised standards so you know which contaminants are covered.
- Help with microbes when needed. Some devices remove or inactivate microorganisms that can cause gastrointestinal illness. Public supplies are disinfected, but point-of-use treatment can add a barrier where risk is higher, for example, on private supplies. Choose products certified for specific microbiological claims.
- Improve taste and smell. Filters can reduce disinfectant residuals and other compounds that cause off-tastes and odours, and remove fine particles so water looks clean.
What do water filters remove?
Below are common contaminants that may be present at low levels in drinking water, why they matter for health, and why many households choose filtration.
- Lead. Lead can leach from older pipework and fittings. There is no safe level of lead in drinking water, particularly for children, due to effects on the brain and central nervous system.
- Nitrate and nitrite. High nitrate in drinking water can cause methaemoglobinaemia in infants. Families using private wells often check nitrate and consider treatment if levels are elevated.
- PFAS (for example PFOA and PFOS). Long-term exposure to some PFAS has been linked with adverse health outcomes. Regulators note that granular activated carbon, ion exchange and reverse osmosis are effective treatment options when systems are certified for PFAS reduction.
- Microplastics. The WHO reports low concern at current levels and highlights important data gaps. Many treatment processes can remove a proportion of microplastic particles. Some consumers still choose filtration as a precaution as microplastics are associated with oxidative stress, immune response, metabolic disorder, neurotoxicity, and more.
Other contaminants can also be reduced or removed, including pesticides, VOCs, microbial contaminants, pharmaceutical residues, and chlorine/chloramine that affect taste and odour.
Combining filtration technologies
Because contaminants vary in size and chemistry, a house water filter system often combines activated carbon with reverse osmosis to cover more ground.
AquaTru, for example, pairs high-grade activated carbon with reverse osmosis and is independently tested by IAPMO to NSF/ANSI standards. Performance Data Sheets for each model are available for review.
Water filtration methods
Most home filtration systems use a mix of physical and chemical processes to clean water. Physical steps strain particles with barriers such as cartridges or membranes. Chemical steps bind, swap, or transform contaminants using media like activated carbon or ion-exchange resins. Many products combine several methods to cover more contaminant types and to improve taste and odour.
Common methods you will see in the water filtration process
- Mechanical filtration that catches sediment, rust and sand.
- Membrane filtration such as microfiltration, ultrafiltration, nanofiltration and reverse osmosis (RO) for finer removal.
- Granular activated carbon for chlorine, chloramine and many organic chemicals that drive taste and odour.
- Ion exchange for dissolved ions such as hardness minerals and some metals.
- UV disinfection to inactivate microbes when needed.
Physical vs. chemical filtration: the key differences
Find the key differences between physical filtration and chemical filtration in the table below, covering how each works, what they target, typical media, strengths, limits, and examples to help you choose appropriately.
|
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Physical filtration |
Chemical filtration |
|
How it works |
Uses a physical barrier to strain particles. Includes microfiltration, ultrafiltration, nanofiltration and RO. |
Uses filters that adsorb contaminants or exchange ions. |
|
Typical targets |
Sediment, rust, sand, microplastics. With fine pores, cysts, bacteria, viruses. |
Chlorine and chloramine, taste and odour compounds, some pesticides/VOCs; hardness ions and some metals. |
|
Common media |
Pleated or depth cartridges, ceramic elements, polymer membranes, RO membranes. |
Activated carbon, ion-exchange resins; some systems add catalytic or sequestration media. |
|
Where it shines |
Clarifies water, protects downstream stages, and with tight membranes can remove very small organisms and dissolved salts (RO). |
Improves taste and smell and targets dissolved chemicals that pass physical screens. |
|
Limits |
Basic cartridges do not change dissolved chemistry. |
Each medium is selective; you must match contaminants to technology and verify claims. |
How do water filter systems purify water? 6 types of filter
Different filters use different science to clean water. Some physically block particles. Others adsorb chemicals, swap ions, or neutralise microbes with light. Many home systems combine methods so they can handle more contaminant types and improve taste. You will find 6 filtration methods below.
1. Reverse osmosis filters
How RO works. Reverse osmosis pushes water through a semi-permeable membrane to separate it from dissolved contaminants.
AquaTru illustrates this clearly in a four-stage flow. It uses a patented four-stage process that pairs carbon with RO to widen protection and refine taste:
- Phase 1: Mechanical filtration. A sediment stage removes large particles such as limescale and rust.
- Phase 2: Pre-carbon filtration. An activated carbon pre-filter reduces chlorine and chloramine and other taste and odour compounds.
- Phase 3: RO membrane. Water is pushed through the reverse osmosis membrane to reduce dissolved contaminants including metals, fluoride, and trace chemicals such as pharmaceutical residues.
- Phase 4: Post-carbon polish. Activated coconut-shell carbon improves taste before the water reaches your glass.
As mentioned above, AquaTru models deliver reliable, independently tested results.
2. Mechanical filters
What they do. Mechanical or sediment filters physically strain particles. They improve clarity and protect downstream stages from clogging.
Typical removals. Rust, grit, sand, and other visible or fine particles. In multi-stage systems they usually act as a pre-filter ahead of carbon and RO.
3. Activated carbon filters
How carbon filters work. An activated carbon filter uses adsorption. Many contaminants stick to its highly porous surface. Carbon has a large internal surface that can easily draw in and trap chemical impurities.
What they target. Strong for chlorine and chloramine and many organic chemicals that affect taste and odour. Depending on the product and certification, carbon stages may also reduce selected pesticides, VOCs, and some disinfection by-products. Carbon is widely used as part of multi-stage filtration systems.
Formats. Granular activated carbon (GAC) and carbon block filters. Blocks increase contact time and often have a micron rating.
4. Sequestration filters
How sequestration works. Sequestration media, often polyphosphates, bind hardness minerals such as calcium and magnesium so they stay in solution and are less likely to form limescale.
Why does it help? It protects appliances and plumbing from scale and supports the performance of downstream filters. It conditions hardness rather than removing it.
5. Ion exchange filters
How ion exchange works. A resin swaps ions. In softening, it replaces calcium and magnesium with sodium or hydrogen to reduce hardness.
Where it is used. Helpful for scale control and to protect membranes. Specialised resins can also target certain heavy metals in the dissolved phase.
6. Ultraviolet (UV) filters
What UV does. UV light inactivates bacteria and viruses by damaging their genetic material.
Important to note. UV is disinfection, not particle removal, so it is usually paired with filtration to clear the water and improve taste. It does not add chemicals to the water.
What is in water filters that remove hardness from drinking water?
Hard water contains higher levels of calcium and magnesium. These minerals form limescale on kettles, pipework, and heating elements. In the UK, hardness varies by region and is often expressed as mg/L as calcium carbonate.
Components that tackle hardness
- Ion exchange resins. These resins swap calcium and magnesium for sodium or potassium, which reduces hardness directly and helps prevent scale. Ion exchange can also reduce small amounts of iron and manganese in some cases.
- Sequestration media. Polyphosphate agents bind hardness minerals so they stay in solution and are less likely to deposit as scale. This controls scale rather than lowering hardness numbers.
- Reverse osmosis membranes. RO can reduce dissolved minerals, which lowers total dissolved solids and softens water at the tap, though most homes use RO for overall contaminant reduction rather than as a whole-house softener.
Benefits of reducing hardness
Reducing hardness can make water feel healthier to drink by improving taste and clarity and helping hot drinks brew cleanly. If you use reverse osmosis to reduce hardness, you can still meet mineral needs through food, and many systems offer optional remineralisation for taste.
The goal is simple: water that is clean, pleasant to drink, and suited to your household.
What type of water filter do I need?
Choosing a filter can feel overwhelming. Keep it simple. Focus on your water, your goal, and what fits your home.
AquaTru is a strong all-round choice for broad coverage and suits most homes. Pick AquaTru Classic for quick, plug-and-play setup in family kitchens. Choose the compact AquaTru Carafe water jug for smaller households or desk-side use. Go with AquaTru Under Sink water filter if you prefer a built-in tap and higher capacity.
Whichever model you choose, replace filters on time and do regular maintenance like descaling to keep performance and taste consistent.
Get access to filtered water with AquaTru
This article has come to an end. You now understand how water filters work and the options available. If you want a high-quality system, AquaTru delivers. Its multi-stage reverse osmosis with activated carbon provides clean, great-tasting water while helping to cut single-use plastic.
AquaTru is simple to install and maintain, making it easy to keep your family and pets hydrated and healthy every day. Choose the model that fits your home and enjoy a reliable source of pure, refreshing water.
Learn more about AquaTru water filters today.
