Whole-house and under-sink filtration systems built with independently certified components — with replacement filters delivered to your door across the UK.
Every Happy H2O system uses standard-format cartridges, so replacements are simple and never overpriced.
800g granular activated carbon + 200g KDF55 in a refillable 10"×4.5" Big Blue housing. Whole-home protection against chlorine, heavy metals, taste and odour.
All-in-one twist-out cartridge — PP, fibre, coconut-shell carbon and nano-silver in a single unit. Change the whole cartridge in seconds, no tools.
Under-sink 3-stage system: PP sediment, 3-in-1 carbon block, and 0.5-micron lead-removal carbon — up to 98.88% lead reduction (IAPMO tested), removes PFOS/PFOA while retaining beneficial minerals.
Sediment + GAC, premium multi-media (antiscale · alkaline · fluoride reduction · KDF55), and resin polishing stage. Comparable systems sell for £220+.
Two questions decide it: do you want better drinking water at the kitchen tap, or treated water at every tap in the house — and how big is your home?
| HK99 — £64.99 | HP99 — £129.99 | |
|---|---|---|
| Best for | Renters, caravans & boats, simple upgrades — twist-out cartridge, no tools | Families who want maximum drinking-water protection |
| Treats | Sediment, chlorine, heavy metals, cysts, asbestos & VOCs, taste & odour | All of that plus 0.5-micron lead removal (up to 98.88%, IAPMO tested) and PFOS/PFOA |
| Cartridges | 1 all-in-one (HKF), change yearly | 3-stage: SED + CB1 + CB2 |
| Filter cost / year | ~£37 | ~£73 |
| Flow | 6 L/min @ 60 psi | Direct connect to your existing tap, with pressure regulator |
| SBB10 — £69.99 | 3S-10BB — £189.99 | |
|---|---|---|
| Best for | Flats and 1–2 bedroom homes; appliance & chlorine protection on a budget | 2–4 bedroom family homes wanting full treatment |
| Stages | 1 — GAC + KDF85 (800g + 200g media, refillable Big Blue) | 3 — sediment + GAC, multi-media (antiscale · alkaline · fluoride reduction · KDF55), resin polishing |
| Treats | Chlorine, heavy metals, taste & odour | Sediment, chlorine, fluoride reduction, limescale prevention, water softening & mineral balance |
| Filter cost / year | ~£39 | ~£89 |
| Fits | Standard 10" systems suit typical UK mains flow — adequate for an average home up to 4 bedrooms (UK guidance: 15–30 L/min peak demand for 3–4 beds). Homes with 3+ bathrooms or high simultaneous use should ask us about higher-flow options. | |
Tip: the two work together — a whole-house system protects your pipes, boiler and appliances, while an under-sink system gives the kitchen tap the highest-grade drinking water. Many households run one of each.
Choose your Happy H2O system and we'll show the right replacement cartridges and when to change them.
Genuine Happy H2O cartridges keep your system performing to spec. Buying direct from us always beats marketplace prices — and you can set a free reminder below so you never miss a change.
5–10 micron polypropylene sediment filter. Removes rust, dirt, sand and particles.
3-in-1 carbon block, 3–5 micron. Reduces chlorine, chloramine, taste, odour and sediment.
0.5-micron lead-removal carbon block. Removes lead, PFOS/PFOA and heavy metals — retains beneficial minerals.
All-in-one twist-out cartridge: PP + fibre + coconut-shell carbon + nano-silver. Reduces cysts, asbestos & VOCs.
10"×4.5" Big Blue cartridge — granular activated carbon + KDF85. Chlorine, heavy metals, taste and odour.
10"×2.5" sediment + GAC cartridge. Removes particles, rust and chlorine.
10"×4.5" premium multi-media: antiscale · antibacterial · alkaline · fluoride removal · KDF55.
10"×2.5" ion-exchange resin + silicon-phosphorus cartridge. Prevents limescale, softens water.
Straight from the owner's manuals — every system installs on the cold line under your sink, no plumber required. Always use the supplied PTFE (plumber) tape on threaded connections for a watertight seal.
Hardness is the amount of dissolved calcium and magnesium in your water, measured in mg/L of calcium carbonate. It's harmless to drink — but it's what furs up your kettle, scales your boiler and shortens appliance life. Most of England is in the hard-to-very-hard bands.
| Classification | mg/L CaCO₃ |
|---|---|
| Soft | 0–50 |
| Moderately soft | 51–100 |
| Slightly hard | 101–150 |
| Moderately hard | 151–200 |
| Hard | 201–300 |
| Very hard | 300+ |
Every UK water company publishes hardness data for its supply zones. Find yours:
Thames Water · Severn Trent · Anglian · United Utilities · Yorkshire · Northumbrian · Southern · South East · South West · Wessex · Affinity · Bristol · Essex & Suffolk · Portsmouth · SES · Cambridge · Bournemouth · Welsh Water · Scottish Water
We publish our component certifications — ask any competitor to do the same.
Jacobi AquaSorb activated carbon — certified for material safety and chlorine/taste/odour reduction.
IAPMO R&T tested to NSF/ANSI 53-2017 (low-pH lead reduction): up to 98.88% reduction. Model HLCB30/11/113.
FLUIDFIT push-fit fittings, WRAS approval No. 260402039, valid to 30 April 2031.
Attestation de Conformité Sanitaire (CARSO Lyon) for FLUIDFIT fittings, valid to 8 September 2027.
Certifications listed apply to the named components and media. Full-system WRAS approval is in progress via NSF Wales.
Our systems use standard cartridge sizes — you'll never be held hostage by a proprietary filter that costs more than the system.
Dispatched from UK warehouses with real support by email. Sold by Smart MCS Ltd, a UK registered company.
Tell us your system and we'll email you when it's time to change your filter — nothing to remember, no subscription required.
NSF/ANSI certified media and WRAS-approved fittings — documentation available on request.
Join the reminder list — we'll email you when your cartridges are due, with a direct reorder link. No spam, unsubscribe anytime.
The things customers ask most — and the practical stuff.
All four systems are designed for DIY installation on the cold line with the supplied hoses, PTFE tape and fittings — see the step-by-step guides above. If you're not confident cutting into your mains for the whole-house systems, any plumber can fit one in under an hour.
Use the Filter Finder above — pick your system and it lists the exact cartridges and when to change them. Each cartridge also has an install-date box on the label so you can write down when it went in.
GAF10, Filter 1, Filter 2 and Filter 3 use standard 10" formats that fit most housings of the same size. SED, CB1, CB2 and HKF are dedicated twist-fit cartridges for Happy H2O systems.
Under-sink systems operate between 20–80 psi (1.4–5.5 bar) — normal UK mains. The SBB10 housing is rated to 125 psi; if your supply can exceed 115 psi, fit a pressure regulator first.
Our carbon media is NSF/ANSI 42 & 61 certified (Jacobi AquaSorb), the HP99's lead-removal media is IAPMO-tested to NSF/ANSI 53 (up to 98.88% reduction), and our push-fit fittings hold WRAS approval No. 260402039 and French ACS. Full details in the Certifications section.
Free UK delivery on orders over £25. Orders are dispatched from UK stock — filters typically arrive within 2–3 working days.
Shop with confidence under UK consumer law: 14-day no-quibble cancellation on online orders, and if anything arrives damaged or develops a fault we'll replace it — contact us before installing and we'll sort it. Inspect the box contents against the manual before installation.