Cylinder selection
We select the right cylinder for the property from the main UK manufacturers — sizing decided by the number of bathrooms, simultaneous use patterns and incoming mains flow rate.
Unvented Hot Water Cylinders · G3 Certified
Unvented hot water cylindersinstalled, serviced and certified —by a G3 qualified engineer.
G3-qualified supply, install, annual service and repair of unvented cylinders. Mains-pressure hot water at every tap, properly engineered and lawfully signed-off.
★★★★★G3 Certificate of Compliance issued · Building Regs notified · Annual servicing keeps manufacturer warranty alive.
18 yearsin plumbing & heating
Gas SafeRegistered — every gas job certified
G3 CertifiedUnvented hot water qualified
Mon–Fri8am–5pm
Fixed priceQuote in writing before work starts
Service overview
Strong mains-pressure hot water, done legally
An unvented cylinder turns a single-bathroom property into a multi-bathroom one — mains-pressure hot water at every tap, no loft tank, no pump needed. But it stores pressurised hot water, which means it has to be installed and serviced by a G3-qualified engineer. We are.
What it is
Design, install, annual service and repair of unvented hot water cylinders to G3 Building Regulations standard. Includes expansion vessel, pressure-reducing valve, temperature & pressure relief valve, tundish, discharge pipework, full commissioning and the G3 Certificate of Compliance.
Who it's for
Homeowners with two-plus bathrooms, families that need hot water at multiple taps simultaneously, properties where loft space is limited or being converted, and landlords or letting agents needing service and certification across Scunthorpe, Hull, Grimsby and Doncaster.
When it's needed
When upgrading from a vented tank-and-cylinder setup, converting a back-boiler property, building an extension that demands more hot water capacity, or when an existing unvented cylinder needs servicing, repair or replacement.
Why a professional matters
Unvented cylinders store water at mains pressure. A failed safety device on an unqualified install is one of the few plumbing failures that can actually injure people. G3 certification is a legal requirement under Schedule G of the Building Regulations — not an optional badge.
What goes wrong
What goes wrong on poorly-installed unvented systems
Most of the unvented cylinder problems we attend in North Lincolnshire are installation problems, not failures of the cylinder itself.
Expansion vessel pressure wrong
Set incorrectly at install, the vessel fails to absorb expansion — the T&P valve discharges every heating cycle. Common, easy to misdiagnose, harder to undo.
Discharge pipework non-compliant
Discharge pipes too small, wrong material, or terminating somewhere they could scald a child. We re-run these to G3 spec regularly.
No annual service, warranty void
Most unvented cylinder manufacturers require an annual service to keep the cylinder warranty active. Skip it and a cylinder failure becomes your problem, not theirs.
PRV failed open
Pressure-reducing valves fail silently. House goes from balanced 3-bar to 5-bar, expansion vessel can't cope, leaks appear on taps and the cylinder relief blows.
Wrong size for the property
An under-sized cylinder trying to feed 3 bathrooms in a 5-person family. Runs cold every evening. Sizing is about capacity AND recovery time.
Immersion heater never tested
The backup immersion sits unused for years, the element corrodes, and when the boiler fails one winter the backup doesn't work either. We test it every service.
Our process
Our unvented cylinder process
Compliant from first survey to G3 certificate.
- 01
Sizing & Survey
Hot-water demand calc based on bathrooms, occupancy, simultaneous use. Mains flow rate measured at the property.
- 02
Fixed Written Quote
Cylinder model, manifold, controls, discharge pipework, all in writing. Three options where helpful.
- 03
Install
Cylinder positioned, primary heating circuit connected, expansion vessel and PRV set to manufacturer spec, T&P discharge pipework run to current G3 standard.
- 04
Commission
System filled, pressurised, vented, tested. Working pressures recorded, controls programmed.
- 05
G3 Certificate & Building Notification
Certificate of Compliance issued and Building Notification submitted. Both posted to you.
- 06
Service & Aftercare
Annual service reminder logged. Service preserves the manufacturer warranty (typically 25 years cylinder, 2 years internals).
Benefits
Why unvented + G3-qualified install matters
Mains-pressure hot water everywhere
Shower in one bathroom while the kitchen tap is running — no pressure drop, no waiting.
Loft space freed
No cold water tank, no F&E tank — loft becomes usable for conversion or storage.
Faster recovery
Modern indirect cylinders re-heat in 25–40 minutes — back-to-back showers without running cold.
Legal compliance
G3 Certificate of Compliance and Building Notification — both required at sale of the property.
Manufacturer warranty active
Annual service keeps your 25-year cylinder warranty live — and we keep the records.
Solar / heat-pump compatible
Twin-coil cylinders ready for future solar thermal or heat-pump integration.
Recent work
Real jobs, real installs.
A few recent unvented cylinders (g3) jobs completed across North Lincolnshire.
In detail
Cylinders, controls and what we install
We work with all the main manufacturers and choose the right cylinder for the property — not the one we have a deal on this week.
Sizing the cylinder
Roughly: 1 bathroom = 125–145l, 2 bathrooms = 170–210l, 3 bathrooms = 250–300l. Adjusted for family size, simultaneous use patterns, and whether high-flow showers are in use.
Twin-coil for solar / heat-pump readiness
If you might add solar thermal or an ASHP later, fit a twin-coil now. The cost difference is small; the future-proofing is significant.
Annual G3 service
What we check every year: working pressure, expansion vessel charge, PRV operation, T&P relief operation, immersion heater test, thermostat and overheat cut-out, discharge pipework condition. All recorded for warranty.
Discharge pipework — the bit that most fails
G3 sets strict rules on D1 (tundish to outside) and D2 (outside) discharge — material, diameter, falls, length, termination position. We re-run non-compliant discharge as standard on any service we attend.
Frequently asked
Straight answers,
in plain English.
Can't see your question? Ring Azim directly on 07576 593045.
What does G3 actually mean?
G3 is Schedule G of the Building Regulations covering unvented hot water systems. Only a G3-certified engineer can legally install, modify or commission one. We're qualified, registered and competent-person scheme members for unvented work.
How much does an unvented cylinder install cost?
Every unvented cylinder install is quoted as a fixed, written price covering cylinder, expansion vessel, PRV, discharge pipework and commissioning.
Do I need a Building Notification?
Yes — every unvented cylinder install is notifiable. We submit the notification and you receive the certificate within 30 days.
How often should an unvented cylinder be serviced?
Annually. It's a manufacturer warranty requirement and a safety best practice. We log the service in your records and remind you 30 days before the next is due.
Can my existing boiler heat an unvented cylinder?
If it's a system or regular boiler with adequate output (typically 18kW+ for a 210l cylinder), yes. A combi cannot — combis are instantaneous, not stored.
How long do unvented cylinders last?
Typically 15–25+ years on a stainless-steel cylinder with annual servicing. The expansion vessel and PRV typically need replacing once or twice in that period.
Can you service one fitted by someone else?
Yes — we service any G3-rated cylinder regardless of who installed it. We'll flag non-compliances we find (without using it as a sales tactic).
What happens if the T&P valve discharges?
It's a safety release — something else is wrong (usually the expansion vessel has lost pressure). Call us; it's a diagnosis and a written quote Mon–Fri.
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Next step
Need an unvented cylinder installed or serviced?
G3-certified engineer, Building Notification handled, annual service reminders. Across Scunthorpe, Hull, Grimsby and Doncaster.
- Gas Safe registered
- G3 certified
- Fully insured
- Family-run · Gas Safe registered 556262
Phone
07576 593045
Based
17 High Burgage, Winteringham, DN15 9NE
Hours
Mon–Fri 8am–5pm · Sat/Sun closed