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G3 qualified plumbers installing and servicing unvented cylinders, immersion heaters and instantaneous water heaters — with the correct safety devices, labelling and paperwork every insurer and building surveyor expects.
G3 qualified · Gas Safe · Building Regs Part G compliant · £2M insured
What it is
Installation, replacement and servicing of unvented cylinders, vented (gravity) cylinders, direct/indirect cylinders, immersion heaters and small point-of-use water heaters.
Who it's for
Homeowners upgrading from gravity systems for better shower pressure, larger homes with multiple bathrooms, and landlords maintaining safe, compliant hot-water systems.
When you need it
When mains pressure allows and you want proper flow at every tap; when replacing a failing cylinder; when converting a heat-only system to include stored hot water.
Why use a professional
Unvented cylinders are pressurised vessels — installation is a G3 matter under Building Regulations Part G. Done incorrectly, the risks are real and serious.
The cheapest time to deal with a plumbing or heating fault is almost always now. Water damage, gas issues and system stress compound quickly — the invoice grows with them.
If you leave it
Common DIY mistakes
You get the same sequence every time — so there are no surprises on the invoice and nothing missed on the job sheet.
We measure incoming mains pressure and flow rate, calculate hot-water demand, and assess airing-cupboard space and discharge routing.
Cylinder model, ancillaries, discharge pipework and controls — quoted fixed.
Cylinder fitted by G3 qualified plumbers with correct safety group: expansion vessel, PRV, T&P valve, tundish, discharge pipe.
Filled, purged, temperature set, thermostat verified, discharge routed safely, labelled to Building Regs.
Benchmark completed, Building Regs Part G notification issued through a competent-person scheme where relevant.
Optional annual service to maintain warranty and safety — expansion vessel pressure checked, safety valves tested.
Unvented systems give you mains-pressure showers throughout the house — no more third-floor dribble.
Legal, insured, correctly notified — no future conveyancing surprises.
Cylinder capacity matched to your bathroom count and household size — hot water that keeps up on Sunday morning.
Tundish and discharge routed to spec — no risk of scalding water venting into the airing cupboard or a loft void.
Benchmark and Building Regs notification issued — the paperwork you'll want at sale time.
Keep the warranty valid and catch weep-stage faults before they become failures.
Hot-water storage is one of the more regulated areas of domestic plumbing. Here's what actually goes in and why every component matters.
Pressurised, mains-fed cylinders — stainless or copper — connected to a boiler (indirect) or heated by immersion (direct). Deliver mains-pressure hot water throughout the property. Installation requires G3 qualification under Building Regulations Part G because of the stored-energy safety implications.
Every unvented cylinder must have: an expansion vessel (absorbs the expansion of heated water), a pressure reducing valve (PRV — keeps incoming pressure below the cylinder rating), a T&P valve (temperature and pressure relief — vents the cylinder if anything goes wrong), and a tundish plus discharge pipe (routes any relief water safely to drain, with a visible air break so you can see if it's discharging).
Older, gravity-fed cylinders with a cold-water storage tank in the loft. Lower pressure, no G3 requirement, cheaper to install and maintain. Perfectly serviceable in the right property; not always the right choice for larger homes or multi-bathroom lifestyles.
Electric heating elements inside the cylinder — usually as a backup or off-peak (Economy 7) heat source. Elements scale up over years, thermostats fail; replacement is straightforward but requires the cylinder to be isolated and drained.
Small under-sink or utility-room water heaters for locations where running a full hot-water line isn't practical — outbuildings, cloakrooms, retrofit utility spaces. Installed with correct isolation, expansion protection and appropriate electrical supply.
Nothing here is generic — these are answers we give West London customers every week.
Ask us directlyLegally, yes. Under Building Regulations Part G, work on unvented cylinders must be carried out by a G3 qualified installer. All our cylinder work is G3.
Quoted fixed after an on-site survey. Price depends on cylinder capacity, incoming mains pressure/flow, discharge routing and any pipework changes.
Rule of thumb: 150L for 1 bathroom, 210L for 2 bathrooms, 250L+ for 3 bathrooms or larger households. We size on actual demand during the survey.
A like-for-like cylinder replacement is typically 1 day. A vented-to-unvented conversion or a new install with new pipework is usually 2–3 days.
Yes. Annual servicing checks expansion vessel pressure, tests safety valves, verifies discharge, and keeps manufacturer warranties valid.
Yes — it's the earliest warning that either the expansion vessel has lost pressure or a safety valve is passing. Book a service visit; don't ignore it.
Combi boilers give mains-pressure hot water instantly, but flow rate is limited to whatever the boiler can heat on-the-fly. For simultaneous demand across multiple bathrooms, a system boiler + unvented cylinder is usually a better answer.
Benchmark commissioning record, manufacturer warranty registration, and Building Regs notification through a competent-person scheme where applicable.
No pressure, no obligation. A Gas Safe engineer visits, scopes the job in person, and puts a written quote in your inbox — usually within 2–3 working days. For emergencies, call the line — it's answered 24/7 by the team, not a call centre.
G3 qualified · Gas Safe · Building Regs Part G compliant · £2M insured
