BBy Bikram Nath·Researched from UK Amazon listings·Updated 2026-09-21·4 products compared
What are the best reverse osmosis systems to buy in the UK?
Our top pick for Reverse Osmosis Systems in the UK is the VIVA21 5-Stage Reverse Osmosis System — Premium Under Sink Water Filtration.
For UK homeowners who want the purest possible drinking water direct from the tap, the VIVA21 5-Stage Reverse Osmosis System is the top recommendation — it is sold as a complete under-sink kit with a lead-free faucet, which matters in homes with older plumbing, and VIVA21 states it is independently tested to NSF/ANSI standards across a wide contaminant range including PFAS, lead and arsenic. If you need zero-TDS water for an aquarium, hydroponics or specialty coffee, the Finest-Filters units with a DI chamber are the better fit; if you want a tank-based system at a lower price, the Naturewater is the practical mid-range option.
Disclosure: As an Amazon Associate I earn from qualifying purchases. This guide contains Amazon affiliate links, and we may earn a commission — at no extra cost to you — but it never changes our rankings.
Reverse osmosis is the most thorough water filtration technology available for UK homes — it removes up to 99% of dissolved solids, heavy metals, fluoride, nitrates, bacteria, PFAS, and even pharmaceuticals that other filter types cannot touch. For UK households, RO is particularly relevant in areas with ageing lead pipework, very hard water (London, South East, East Anglia), or where tap water taste is a persistent concern. The technology works by forcing water through a semi-permeable membrane under pressure, leaving contaminants behind in a waste stream. Modern tankless RO systems have addressed two historic UK objections: space (they are now compact under-sink units) and wastewater (the best 2026 models achieve 1:1 or 2:1 pure-to-drain ratios). Installation requires connection to your cold water supply and a drain — a DIY-capable job for most UK homeowners in 1–2 hours, or a quick job for any plumber.
Buying guide
What should you look for in Reverse Osmosis Systems?
1Check the pure-to-drain ratio before buying — cheaper RO units waste 3–5 litres of water for every litre of pure water produced; modern units achieve 1:1 or 2:1.
2Tankless RO systems save under-sink space compared with tank-based designs; a storage tank takes more cupboard room but keeps filtered water ready to draw instantly.
3GPD (gallons per day) rating matters for flow rate: 50–100 GPD suits most families, and tank-based systems store filtered water so the GPD figure matters less day to day.
4NSF/ANSI certification on the membrane and housing verifies contaminant reduction claims independently — look for this label.
5Budget for an annual membrane and filter replacement — typically £30–£60 per year depending on the system brand.
Our process
How do we choose our picks?
We don’t lab-test products ourselves. Instead we synthesise the strongest independent evidence — current Amazon UK listings, verified-buyer feedback, published specs and UK pricing — into clear, honest recommendations. We earn a commission if you buy through our links, but that never changes which products we rank.
Current UK availability
We check each pick against live Amazon UK catalogue data rather than last year’s model lists. Stock moves fast, so a listing can sell out after we publish.
Publicly visible buyer feedback
We look at how each product is received by UK shoppers — its overall rating standing and the praise or complaints that recur in public reviews — rather than relying on a single reviewer’s opinion.
Published specs & value
We compare manufacturer specifications, typical UK price bands, warranty and running costs so each pick is right for a real budget and use-case.
UK-specific fit
We factor in UK voltage, plug/fitting standards, CE/UKCA marking and Consumer Rights Act cover — details that generic global lists miss.
PFAS, chlorine, fluoride, lead, arsenic, asbestos and more
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Heavy metals, pesticides, hormones, bacteria, protozoa, nitrates, phosphates
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Di Resin
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Included — reduces TDS to 0
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High-quality DI resin — TDS to 0
Available Sizes
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50GPD, 75GPD, 100GPD
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50GPD, 75GPD, 100GPD
The rankings
The best Reverse Osmosis Systems, ranked
1
VIVA21
Best Certified
VIVA21 5-Stage Reverse Osmosis System — Premium Under Sink Water Filtration
VIVA21 positions this as a premium health-first system — independently tested against NSF standards for a wide range of contaminants including PFAS and arsenic. The included lead-free faucet is a thoughtful addition for UK homes. A credible choice if you want certification-backed assurance on a complete system.
Stages
5-stage filtration
Contaminants Removed
PFAS, chlorine, fluoride, lead, arsenic, asbestos and more
Finest-Filters Reverse Osmosis RO Unit with Booster Pump and DI Stage 50GPD
The Finest-Filters RO unit with booster pump and DI stage is the specialist choice — it produces genuinely zero-TDS water, which matters for aquarium keepers, hydroponic growers, and specialty coffee enthusiasts. Not the right buy for everyday drinking water production, but unmatched for purity-demanding applications.
Stages
4-stage with DI chamber
Flow Rate
50 GPD
Booster Pump
Di Resin
Included — reduces TDS to 0
Auto Flush
Pressure Gauge
Available Sizes
50GPD, 75GPD, 100GPD
What we like
+Built-in booster pump ensures optimal pressure — works even with low UK mains pressure
+Auto membrane back-flush extends membrane life significantly
+DI chamber reduces TDS to 0 — essential for aquariums, specialty coffee, lab use
Worth noting
–More complex than consumer-grade units — aimed at technical users and aquarium hobbyists
–Slower flow rate at 50 GPD
£144.99Amazon.co.uk price as of 08 Oct, 19:00 (London time). Details
Naturewater Reverse Osmosis System 190L/day NW-RO50-NP35 with Storage Tank
The Naturewater RO unit offers solid 5-stage filtration with a storage tank included at a competitive price. The traditional tank-based design is less space-efficient than a tankless unit but delivers reliable broad-spectrum filtration for drinking water. A practical mid-range choice for UK households who want complete RO without the premium price.
Stages
5-level filtration
Flow Rate
190 litres/day (max)
Membrane
50 GPD
Contaminants Removed
Heavy metals, pesticides, hormones, bacteria, protozoa, nitrates, phosphates
Tank
Included
Installation
Under-sink
What we like
+Complete system with storage tank included — no separate tank purchase needed
+Filters heavy metals, pesticides, hormones, and bacteria — broad-spectrum protection
+Competitively priced for a 5-stage system with tank
Worth noting
–Dispatched within 7–8 days — longer delivery than Prime alternatives
–Tank-based design takes more under-sink space than tankless systems
£95.99£99.99−4%Amazon.co.uk price as of 08 Oct, 19:00 (London time). Details
Finest-Filters 100GPD 4-Stage Reverse Osmosis RO Unit with DI Chamber
The 100 GPD Finest-Filters unit without the booster pump is the lower-cost entry into zero-TDS RO filtration. It fits standard UK 15mm copper pipework directly, which simplifies installation. If your mains pressure is adequate, this produces the same zero-TDS output as the pumped model at a lower cost.
Stages
4-stage with DI chamber
Flow Rate
100 GPD
Di Resin
High-quality DI resin — TDS to 0
Connections
Waste water clamp valve + self-piercing feed valve for 15mm copper pipe
Available Sizes
50GPD, 75GPD, 100GPD
What we like
+100 GPD flow rate — faster production than the 50 GPD model
+Self-piercing feed valve for 15mm copper pipe — fits standard UK plumbing
+DI resin stage for zero-TDS output
Worth noting
–No booster pump — requires adequate mains water pressure
–Minimal product description and no feature bullet points — buy from a trusted reseller
View on Amazon UKAmazon UK shows no offer for this product as of 08 Oct, 19:00 (London time). Details
Product prices and availability are accurate as of 08 Oct, 19:00 (London time) and are subject to change. Any price and availability information displayed on Amazon.co.uk at the time of purchase will apply to the purchase of this product.
Editor's Note
UK mains water pressure typically runs 1–3 bar, which is sufficient for most RO membranes without a booster pump. If you are in an older property with low pressure or a gravity-fed system, a booster pump is essential — without it, membrane efficiency drops and wastewater ratio worsens significantly. Tank-based systems store filtered water so you are not waiting on the membrane, at the cost of cupboard space and a tank that needs periodic sanitising. Annual running costs are modest — typically £30–£60 for filter cartridges and membrane replacement.
Our Take
The VIVA21 5-stage system is the RO to buy for most UK kitchens — VIVA21 states it has been independently tested to NSF/ANSI standards for PFAS, fluoride, lead and arsenic, which chlorine-only filters cannot touch, and it arrives as a complete under-sink package with a lead-free faucet rather than a parts list.
Questions & answers
Frequently asked questions
Is reverse osmosis water safe to drink in the UK?
Yes. RO water is safe to drink. It removes most dissolved minerals alongside contaminants, which some people address by remineralising via an alkaline filter stage. For healthy adults, RO water is perfectly fine. It is the preferred choice for specialty coffee, baby formula, and households with older lead pipework.
Does reverse osmosis remove limescale in UK hard water?
Yes — this is one of the primary reasons UK households in hard water areas install RO systems. The membrane removes calcium and magnesium ions responsible for limescale, producing noticeably softer water that is kinder to kettles, coffee machines, and dishwashers.
How much does it cost to run an RO system in the UK?
Running costs are primarily filter and membrane replacements — typically £30–£60 per year depending on the system and your water quality. Electricity use for pumped systems is minimal (5–20W). Modern RO systems with 1:1 or 2:1 drain ratios have also addressed the historic wastewater concern.
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