Undersink Reverse Osmosis
A second tap at your kitchen sink delivering filtered drinking water — pure enough to taste the difference. No tank, no plastic bottles, no replacement jugs. Just pull, pour, drink.
What it is
A compact filtration system that lives under your kitchen sink, plumbed straight off your cold mains. Four stages of filtration strip out almost everything — including PFAS — and deliver clean drinking water to a dedicated tap fitted next to your existing mixer.
It runs on demand. There's no tank taking up cupboard space, no waiting for water to fill, no stale water sat in storage. Pour a glass in eight seconds straight from the source.
How the 4-stage system works
Mains water enters the unit and passes through four filtration stages before reaching the drinking tap. Each stage handles a different job — and by the time water reaches the glass, up to 99.8% of common contaminants have been removed.
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1
Spun polypropylene — sediment trap
Catches sand, rust, scale particles and pipework debris carried in from the mains. First line of defence — protects the more sensitive media downstream.
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2
Carbon block — chemical filter
Strips out chlorine, organic compounds and the chemical taste that puts people off drinking from the tap. Also protects the membrane in stage three.
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3
Reverse osmosis membrane — the serious one
Sub-nano filtration removes calcium ions, fluorine, organic matter, heavy metals (including lead), chloramines, PFAS, PFOS, bacteria and viruses. Removes up to 99.8% of contaminants by weight.
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4
Final carbon polish — taste & odour
A final carbon stage tunes the taste and odour. What you actually notice in the glass.
Optional fifth stage — remineralisation cartridge. Reverse osmosis strips everything, including healthy minerals. If you want calcium and magnesium added back into your drinking water, a remineralisation cartridge is available as an upgrade.
How the install works
Step 1 — Free on-site water survey
Jordan visits, tests your mains supply, talks through how you use water, and recommends the right configuration. Twenty minutes. No pressure.
Step 2 — System designed around your kitchen
Pricing in writing. Tap finish, dedicated tap position, cabinet space — all agreed before anything is ordered.
Step 3 — Install day — typically 2 to 3 hours
Cold mains tapped, unit mounted, drinking tap drilled into your sink or worktop, leak-tested, flushed. The system is online before Jordan leaves.
Step 4 — Aftercare & filter changes
Filters typically need replacing every 12 months. Either you call us when due, or join the maintenance subscription and we handle it automatically.
What it costs
Honest pricing. Your install matches your kitchen, your water, and your usage — not a one-size-fits-all kit.
- Basic 4-stage install. 1-person flat, straightforward plumbing.
- Standard family install. 4-person home, dedicated tap, full leak protection.
- Premium with remineralisation. Premium tap finish, remineralisation upgrade, commercial-grade leak shutoff.
Every install is quoted individually and confirmed in writing after the free 20-minute on-site survey — the price depends on tap finish, cabinet layout, and whether a new tap hole is needed.
Includes the system, dedicated drinking tap, full plumbing, leak protection, commissioning, and a year of aftercare. No call-out fees. No subcontractors.
What's included as standard
- 4-stage filtration system
- Dedicated drinking tap (chrome standard; brushed nickel, matt black, copper, gunmetal as options)
- All cold mains tapping and pipework
- Built-in leak protection
- LED filter-change indicator
- 2-year workmanship warranty
- 12-month filter set
- Plain-English aftercare brief
- One follow-up call at 6 weeks to check satisfaction
Undersink RO is right for you if…
- You currently buy bottled drinking water.
- You don't like the taste of your tap water.
- You make a lot of tea or coffee.
- You're worried about PFAS, chlorine or lead in mains supply.
- You want clean drinking water without the cupboard space of a tank-based system.
Probably not right if…
- You want every tap in the house filtered — see Whole-House Water Filtration.
- You want instant boiling water from the same tap — see 4-way Boiling Tap Installation.
- Your priority is removing limescale — talk to us about a softener via Bespoke System Design.
Frequently asked questions
How much does an undersink RO system cost installed?
Every install is quoted individually and confirmed in writing. The price depends on tap finish, cabinet layout, remineralisation options, and whether a new tap hole is needed. Free 20-minute on-site survey for an accurate quote.
How fast does an undersink RO system produce water?
Direct-flow RO systems run at about 90 litres per hour, filling a glass in around 8 seconds. The 600 GPD (gallons-per-day) membrane is more than most homes ever use. No tank needed — water is produced on demand.
How long does the install take?
Most installs take 2–3 hours. Up to half a day if a new tap hole needs drilling into a stone or composite worktop.
How often do RO filters need changing?
Sediment and carbon filters every 12 months. The RO membrane lasts 24–36 months. We track this for you if you're on the maintenance plan, or you can call us when due.
Does reverse osmosis remove PFAS?
Yes. Reverse osmosis is one of the most effective domestic methods for removing PFAS (per- and polyfluoroalkyl substances, the "forever chemicals" increasingly found in UK mains water). The 4-stage system reduces PFAS content by up to 99%.
Will RO water taste flat?
Some people notice. Reverse osmosis removes everything including healthy minerals. We offer an optional remineralisation cartridge as a fifth stage which adds calcium and magnesium back in. Most customers find pure RO water simply tastes clean rather than flat.
Other services
Undersink Water Chiller
Pairs naturally with an RO system — the chiller sits after the filter, so the same dedicated tap area serves filtered and chilled.
Learn more →Whole House Water Filtration
Point-of-entry system treating every tap in the house. The big upgrade — bathrooms, showers, every appliance.
Learn more →4-way Boiling Tap Installation
Instant boiling, filtered cold drinking, plus standard hot and cold from a single tap. Replaces your kettle.
Learn more →Bespoke System Design
Unusual property, water profile or contaminant concern — designed and installed to fit.
Learn more →Book your free 20-minute survey
Tell us where you are and what you're after. We'll come back within 1 working day.