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The question I get asked most often: "Keith, I don't want to mess about. I want the best. What do I need to get the cleanest water I can for my family?"
Fair enough. After 25 years working with industrial filtration and 18 years building RO/DI purified-water systems, I've learned that some people want the research, and some people just want the answer. This guide gives you both.
The Short Answer
For most UK homes on mains water: A 5-stage reverse osmosis (RO) system with remineralisation will remove 95-99% of all contaminants including lead, PFAS, microplastics, bacteria, and dissolved solids. Cost: £150-300. DIY installation possible.
For complete sterility (well water, immunocompromised family members): Add a UV steriliser after the RO system. This kills any remaining bacteria and viruses. Additional cost: £100-200.
For hard water areas: Install a water softener before the RO system to protect the membrane and extend its life. Additional cost: £400-800.
Now, if you want to understand WHY these recommendations work, and which specific setup is right for YOUR situation, read on.
Understanding Filter Sizes
Different contaminants are different sizes. To remove them, you need a filter with holes smaller than the contaminant. Here's our visual guide:
Key takeaway: Only reverse osmosis (0.0001 microns) removes dissolved contaminants like PFAS, heavy metals, and dissolved solids. Carbon filters and jug filters cannot do this - they're too coarse.
Find Your Scenario
Your ideal setup depends on your specific situation. Find yours below:
Standard UK Mains Water
Most UK homes on mains water supply
Main Concerns
- Chlorine taste
- Microplastics
- PFAS
- Lead (older pipes)
Recommended Solution
5-stage RO system with remineralisation
What You'll Need:
| Product | Purpose | Est. Cost |
|---|---|---|
| 5-Stage RO System | Core filtration | £150-300 |
| Remineralisation cartridge | Adds minerals back | £20-40 |
| Total Estimated Cost | £170-340 | |
Low Water Pressure
Flats, older properties, gravity-fed tanks
Main Concerns
- Insufficient pressure for RO
- Slow flow rate
- System inefficiency
Recommended Solution
RO system with booster pump
What You'll Need:
| Product | Purpose | Est. Cost |
|---|---|---|
| 5-Stage RO System | Core filtration | £150-300 |
| Booster pump | Increases pressure to 60+ PSI | £50-100 |
| Pressure gauge | Monitor pressure | £10-15 |
| Total Estimated Cost | £210-415 | |
Hard Water Areas
London, South East, East Anglia, Midlands
Main Concerns
- Limescale buildup
- Membrane damage
- Reduced filter life
Recommended Solution
Water softener + RO system
What You'll Need:
| Product | Purpose | Est. Cost |
|---|---|---|
| Water softener | Removes hardness before RO | £400-800 |
| 5-Stage RO System | Core filtration | £150-300 |
| Anti-scale cartridge | Extra protection | £30-50 |
| Total Estimated Cost | £580-1,150 | |
Private Well/Borehole
Rural properties not on mains supply
Main Concerns
- Bacteria
- Nitrates
- Pesticides
- Heavy metals
- Unknown contaminants
Recommended Solution
Multi-barrier system with UV
What You'll Need:
| Product | Purpose | Est. Cost |
|---|---|---|
| Sediment pre-filter (20 micron) | Remove particles | £30-50 |
| Carbon block filter | Remove chemicals | £40-60 |
| 5-Stage RO System | Core filtration | £150-300 |
| UV steriliser | Kill bacteria/viruses | £100-200 |
| Annual water test | Monitor quality | £50-150 |
| Total Estimated Cost | £370-760 + annual testing | |
Immunocompromised Family
Cancer patients, transplant recipients, HIV/AIDS, elderly
Main Concerns
- Cryptosporidium
- Giardia
- Bacteria
- Any pathogens
Recommended Solution
RO + UV + 0.2 micron final filter
What You'll Need:
| Product | Purpose | Est. Cost |
|---|---|---|
| 5-Stage RO System | Remove 99%+ contaminants | £150-300 |
| UV steriliser | Kill all pathogens | £100-200 |
| 0.2 micron final filter | Absolute bacteria removal | £40-60 |
| TDS meter | Verify system working | £10-20 |
| Total Estimated Cost | £300-580 | |
Note: NHS recommends boiling water OR using RO+UV for immunocompromised patients
Baby Formula Preparation
Families with infants under 12 months
Main Concerns
- Lead
- Nitrates
- Bacteria
- Fluoride levels
Recommended Solution
RO system (removes fluoride - may need supplementation)
What You'll Need:
| Product | Purpose | Est. Cost |
|---|---|---|
| 5-Stage RO System | Remove all contaminants | £150-300 |
| Remineralisation cartridge | Balanced minerals | £20-40 |
| Total Estimated Cost | £170-340 | |
Note: Discuss fluoride supplementation with your health visitor if using RO water
Special Dietary Requirements
Low sodium diets, kidney patients, specific mineral needs
Main Concerns
- Sodium from softeners
- Mineral balance
- TDS levels
Recommended Solution
RO with specific remineralisation
What You'll Need:
| Product | Purpose | Est. Cost |
|---|---|---|
| 5-Stage RO System | Remove everything | £150-300 |
| Alkaline remineraliser | Add specific minerals | £30-50 |
| TDS meter | Monitor mineral content | £10-20 |
| Total Estimated Cost | £190-370 | |
Note: Consult your doctor about specific mineral requirements
The Multi-Barrier System Explained
A complete water filtration system uses multiple stages, each removing different contaminants. Here's what each stage does and why it matters:
Sediment Pre-Filter
5-20 microns • Lifespan: 6-12 months • Replacement: £10-20
Purpose: Protects downstream filters from clogging
Carbon Pre-Filter
5-10 microns • Lifespan: 6-12 months • Replacement: £15-25
Purpose: Protects RO membrane from chlorine damage
RO Membrane
0.0001 microns • Lifespan: 2-3 years • Replacement: £30-60
Purpose: Core filtration - removes 95-99% of contaminants
Carbon Post-Filter
1-5 microns • Lifespan: 12 months • Replacement: £15-25
Purpose: Final polish for taste
Remineraliser
N/A • Lifespan: 12 months • Replacement: £20-40
Purpose: Adds calcium, magnesium, raises pH
UV Steriliser (Optional)
N/A • Lifespan: 12 months (bulb) • Replacement: £30-50 (bulb)
Purpose: Absolute sterility for vulnerable users
Critical: Check Your Water Pressure First
⚠️ Before you buy ANY RO system, you MUST check your water pressure.
RO systems need minimum 40-60 PSI to work efficiently. If your pressure is lower, the system will produce water very slowly and waste more water during the purging process.
How to Test:
- Buy a water pressure gauge (£10-15 from any hardware store or Amazon)
- Attach it to an outside tap or washing machine connection
- Turn on the tap fully and read the gauge
- Test at different times of day (pressure varies)
✓ 40+ PSI: You're Good
Standard RO systems will work fine. No pump needed.
✗ Below 40 PSI: Need a Pump
You'll need a booster pump (£50-100) to increase pressure before the RO system.
Annual Running Costs
| Component | Replace Every | Annual Cost |
|---|---|---|
| Sediment pre-filter | 6-12 months | £15-30 |
| Carbon pre-filter | 6-12 months | £20-40 |
| RO membrane | 2-3 years | £15-25/year |
| Post-filter & remineraliser | 12 months | £30-50 |
| UV bulb (if fitted) | 12 months | £30-50 |
| Total Annual Running Cost | £80-195 | |
Compare to bottled water: A family of 4 drinking 2L each per day spends approximately £500-1,000 per year on bottled water. An RO system pays for itself within 6-12 months.
Frequently Asked Questions
Does RO water taste "flat"?
Pure RO water can taste flat because minerals are removed. That's why I always recommend a remineralisation stage - it adds back calcium and magnesium, raises the pH slightly, and gives the water a pleasant, natural taste.
How much water does RO waste?
Traditional RO systems waste 3-4 litres for every 1 litre produced. Modern "zero-waste" systems recirculate this water, reducing waste significantly. However, even with standard systems, the cost is minimal - about £10-20 per year in water bills.
Can I install this myself?
Most under-sink RO systems are DIY-friendly if you're comfortable with basic plumbing. You'll need to connect to the cold water supply and drain. If you're adding a water softener or have complex requirements, I'd recommend professional installation.
What about whole-house filtration?
Whole-house RO is expensive (£2,000-5,000+) and usually unnecessary. Most contaminants of concern are only an issue when ingested. A point-of-use system at your kitchen tap is more practical and cost-effective for drinking water.
Final Thoughts
Look, I've spent 25 years in industrial filtration and 18 years building RO/DI systems. I've seen every situation imaginable — from worried new parents to immunocompromised individuals needing the highest level of protection, from rural farmhouses on well water to London flats with Victorian lead pipes.
The truth is, UK mains water is already safe to drink for most people. Water companies are legally required to meet strict standards. But "safe" and "optimal" aren't the same thing.
If you want the peace of mind that comes from knowing your water is as clean as it can possibly be - free from microplastics, PFAS, lead, and everything else - then a properly configured RO system is the answer.
And if you're not sure which setup is right for you, take our quiz or check your water quality first. Don't buy something you don't need - but don't compromise on your family's health either.
— Keith Wilks, Filter Authority
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