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Domestic
One point of use, a compact stack of stages under a sink, feeding a dedicated drinking tap.
- Sized by household drinking demand
- Compact cartridge-based pretreatment
- Small membrane and pressure storage tank
How water treatment works
From raw water to reliable water
A treatment plant is a sequence of stages, each one solving a different problem and each one chosen because of what the incoming water actually contains. This is what happens between the supply and the outlet.
PretreatmentPressureMembranePolishing
The core idea
The plant is a sequence, not a single filter
Each stage solves a different problem, and each one exists because of something specific in the water. Remove one and the stage after it starts doing work it was never designed for.
- 01
Source
What arrives, and what it carries
- 02
Pretreatment
Remove what would damage the membrane
- 03
Pressure
Drive water against the membrane
- 04
Membrane
Separate water from dissolved solids
- 05
Polishing
Condition what comes through
- 06
Storage
Hold it and deliver it at the outlet
The treatment journey
Nine stages, and what each one is actually for
Select a stage to see what it does, what it protects and whether it appears in every plant.
Stage 01 · Standard
Raw water inlet
Where the supply enters, and where the design begins
Water arrives from a mains connection, a bore, a tanker or a storage tank, and what it carries is the single biggest influence on everything downstream. Two buildings on the same road can receive water that needs different treatment. This is why a plant is designed after an analysis rather than picked from a catalogue.
- Decides
- Every stage that follows it
Stage 02 · Standard
Sediment & multimedia filtration
Takes out suspended solids before anything finer sees them
A bed of graded media traps sand, silt, rust and other suspended matter. It is the coarse work, and it exists so that the finer, more expensive stages are not asked to do it. A supply carrying heavy sediment loads this stage hard, which is why the media is sized against the water rather than the building.
- Protects
- Cartridge filters, pump and membrane
Stage 03 · Configuration dependent
Carbon filtration
Removes chlorine and organics that attack membrane material
Activated carbon adsorbs chlorine and a range of organic compounds. This matters mechanically rather than cosmetically: the thin film used in RO membranes is damaged by continuous chlorine exposure, so where the supply is chlorinated, carbon sits upstream of the membrane to take it out first.
- Protects
- The membrane surface from chlorine
Stage 04 · Configuration dependent
Softening
Exchanges the hardness that would otherwise scale the membrane
Hard water carries calcium and magnesium that precipitate onto membrane surfaces and reduce what a plant can produce. An ion exchange softener swaps those ions out before the water reaches the membrane. Whether it is fitted, and how it is sized, comes from the hardness in the analysis.
- Handles
- Hardness, where the analysis shows it
Stage 05 · Standard
Cartridge filtration
The last mechanical guard before the pump and membrane
A replaceable cartridge catches the fine particles that survived the earlier stages. It is the cheapest component protecting the most expensive one, and it is deliberately consumable — a cartridge that blocks is doing its job and telling you something about the supply.
- Protects
- The high pressure pump and the membrane
Stage 06 · Standard
High-pressure pump
Supplies the pressure that makes separation possible
Reverse osmosis does not happen on its own. The feed has to be pushed against the membrane hard enough to overcome the osmotic pressure of the dissolved solids in it. The pump provides that, and the operating point it is set to depends on the membrane, the feed water and the output the plant is designed for.
- Delivers
- The driving force across the membrane
Stage 07 · Standard
RO membrane
Where the separation actually happens
Under pressure, water passes through a semi-permeable layer while most dissolved solids do not. What gets through is product water; what does not is carried away as concentrate. This is the stage that changes what a TDS meter reads, and every stage before it exists to keep it working.
- Separates
- Water from most dissolved solids
Stage 08 · Configuration dependent
Post-treatment & polishing
Conditions what the membrane has produced
Depending on what the water is for, treated water may pass through a post-carbon stage for taste, a UV or UF stage where disinfection is specified, or mineral conditioning. None of these is automatic. They are specified for an application, not fitted as standard.
- Configured for
- The application, not the catalogue
Stage 09 · Standard
Storage & distribution
Holds treated water and delivers it where it is needed
Treated water is stored so that supply meets demand at the moment of use rather than the moment of production. Tank size, material and the distribution arrangement follow from the daily requirement and the layout of the building.
- Matches
- Production to actual demand
Actual configuration depends on feed-water analysis and required output quality. Not every plant contains every stage.
Before the membrane
Why pretreatment matters
A membrane is the most expensive component in the plant and the least tolerant of what arrives at it. Almost everything that shortens a membrane’s life is something that should have been dealt with upstream.
- Sediment removal
- Traps sand, silt and rust carried in the supply.
- Wherever the water arrives with suspended solids.
- Carbon filtration
- Adsorbs chlorine and organic compounds.
- Where the supply is chlorinated or carries organics.
- Softening
- Exchanges the calcium and magnesium that cause scaling.
- Where the hardness in the analysis warrants it.
- Cartridge filtration
- Catches the fine particles the earlier stages missed.
- Standard ahead of the pump and membrane.
Stage 07
Where separation happens
Under pressure, water passes through a semi-permeable layer and most dissolved solids do not. Everything before this stage protects it; everything after it conditions what it produces.
Feed water
Enters the housing under pressure from the booster pump.
Semi-permeable layer
Water molecules pass. Dissolved solids do not.
Product water
Spirals inward to the centre tube and leaves as treated water.
Concentrate
Carries the rejected solids away to drain.
A membrane also produces a concentrate stream. An RO system uses more water than it makes — how much more is a property of the design and the feed water, not a fixed number.
Pressure & flow
Why the high-pressure pump exists
- Pressure is the driving force
- Left alone, water moves from the less concentrated side of a membrane to the more concentrated side. Reverse osmosis pushes it the other way, and pressure is what does the pushing.
- The operating point is not universal
- What a system needs depends on the membrane fitted, the dissolved solids in the feed and the output the plant is designed to produce. A figure that is right for one plant is wrong for another.
- Flow and pressure are read together
- Pressure alone says little. Read alongside product flow and outlet quality, it is how you tell a healthy plant from one that is starting to foul or scale.
This page does not publish operating pressures. A figure that suits one membrane and one feed water is misleading applied to another, and the right one comes out of the system design.
After the membrane
Treatment doesn't end at the membrane
What happens to product water depends on what it is for. These stages are specified for an application rather than fitted as standard.
Where specified
Post-carbon polishing
A final carbon stage, used where taste and odour are a consideration.
Where specified
UV or UF disinfection
Fitted where disinfection is specified for the application rather than as a default part of every system.
Where specified
Mineral conditioning
Reintroduces selected minerals after the membrane, where that is part of the specification.
Standard
Storage
Treated water is held so that production and demand do not have to coincide. Sizing follows the daily requirement.
Standard
Distribution
Pipework, pumping and outlets that get treated water to the point of use, arranged around the building rather than the plant.
Scale
Same process. Different system.
The principle does not change between a kitchen and a factory. What changes is the source, the quality required, the demand and the application — and every one of those changes the plant.
Building
Commercial
A plant serving a whole facility, where downtime is the thing the design has to defend against.
- Sized on survey and peak demand
- Vessel-based pretreatment selected from the analysis
- Storage and distribution designed around the building
Process
Industrial & custom
Built to a process requirement, where the water quality is an input to something else rather than an end in itself.
- Designed against a process specification
- Pretreatment train built for the source
- Controls and monitoring to suit the operation
Actual configuration depends on feed-water analysis and required output quality. Not every plant contains every stage.
Your water
Want to know what your water actually needs?
The answer starts with a reading, not a recommendation. Tell us the building and the source and we will test the supply. Or call 0300-4334482.