JAB Cylinders: A Family-Run British Manufacturer Delivering Quality Since the 1980s
When it comes to hot water cylinders, installers and specifiers want products they can trust — built to last, competitively priced, and backed by a manufacturer that understands the realities of life on site. JAB Products ticks every one of those boxes. A proudly British, family-run business with roots stretching back to 1956, JAB has spent decades quietly building one of the most comprehensive cylinder ranges on the UK market, from compact direct unvented units for domestic airing cupboards right through to 500-litre Hi-Flo commercial cylinders for restaurants and salons.
In this guide, we take a closer look at the full JAB product range, the company's heritage, and why their cylinders have earned a loyal following among independent merchants and tradespeople across the country.
The JAB Story: Three Generations of British Manufacturing
J.A. Bunyan Ltd was founded in 1956 by James Alexander Bunyan as an independent hot water product distributor. His son Michael created JAB Products in the 1980s, spotting a gap for quality, competitively priced cylinders aimed squarely at the independent merchant network. Today the business is led by Michael's sons, James and Oliver — the third generation — continuing the family mission of delivering cost-efficient, British-made hot water products.
JAB Products launched as an alternative to traditional copper cylinders, then entered the unvented market with the JAB Duc 1.
Expanded with the Duc IE (internal expansion), the Duc 2 range (horizontal and slimline options), and the DOV vented range — a Duplex stainless steel upgrade to the copper cylinder.
Relaunched the Duc IE Compact with pre-plumbed options and introduced the JAB TSC thermal store for apartments where discharge pipework is prohibited.
Launched the Hi-Flo range (28mm inlets, up to 500L) for light commercial use. The JAB EMU 10L and 15L electric multipoint water heaters are due by end of 2026.
Proudly Manufactured in Britain
Every JAB cylinder is built in the UK using premium Duplex stainless steel
UK Manufactured
All JAB cylinders are designed and manufactured in the United Kingdom, supporting British jobs and ensuring short supply chains for fast merchant delivery.
Duplex Stainless Steel
Every unit is built from premium Duplex grade stainless steel, providing superior corrosion resistance and long-term durability compared to standard grades.
Full Spares Availability
JAB works in partnership with spare-part providers, so replacement thermostats, immersions, and safety valves are always available — keeping cylinders serviceable for years.
Shrink-Wrapped & Boxed
Every cylinder arrives shrink-wrapped to confirm unused condition and boxed for transit protection — reducing site damage claims and merchant returns.
The Full JAB Cylinder Range — By Type & Application
JAB currently manufactures six distinct product families, each targeting a different installation scenario. Every range shares the same core qualities — Duplex stainless steel construction, 316L grade fittings, and thoughtful design for real-world installation — but each solves a different problem on site.
JAB Duc 2 — External Expansion
The Duc 2 is JAB's flagship unvented cylinder range and the backbone of their domestic offering. Built from Duplex stainless steel with 316L grade 22mm compression fittings, these cylinders are designed for straightforward installation into existing airing cupboards as a direct upgrade from traditional copper cylinders. The 22mm primary coils provide increased surface area for quick recovery times, and capacities span from 90 litres right up to 500 litres across direct, indirect, slimline, horizontal, and solar twin-coil configurations.
JAB Duc IE — Internal Expansion
The Duc IE is JAB's compact, internal-expansion unvented cylinder. By building the expansion vessel inside the cylinder shell, the IE eliminates the need for a separate wall-mounted expansion vessel — saving space and simplifying pipework. This makes it ideal for tight airing cupboards, utility rooms, and specification-led projects where every millimetre counts. Available in standard and slimline profiles in both direct and indirect configurations, the IE Compact (relaunched in 2020) also introduced pre-plumbed options for faster installation.
JAB DOV — Duplex Open Vented
The DOV (Duplex Open Vented) range was introduced in 2014 to give homeowners and installers a modern, high-quality upgrade path from the traditional foam-lagged copper cylinder. At just 470mm wide — the same or narrower than a standard copper cylinder — the DOV is designed for retro-fit as well as new-build applications. Despite the compact shell, JAB has fitted 1" cold feed, 1" hot draw-off, and 1" secondary return connections as standard, ensuring the DOV delivers strong flow rates even in larger dwellings or properties with luxury shower systems. The indirect model includes a 22mm high-performance coil, cylinder thermostat, and a single 3kW immersion heater, while the direct model comes with 2 x 3kW immersions for Economy 7 compatibility. For properties with good mains pressure considering an upgrade, see our full range of unvented cylinders.
JAB TSC — Thermal Store Cylinder
Launched in 2022, the JAB TSC is an open-vented thermal store that solves one of the most common installation headaches in apartment buildings: the discharge pipe. Because the TSC operates at atmospheric pressure rather than mains pressure, it requires no temperature and pressure relief valve and no discharge pipework — eliminating the Part G compliance issue that prohibits routing a discharge pipe into a soil stack. Cold mains water passes through an internal heat exchanger coil, picking up heat from the stored primary water and delivering mains-pressure hot water to taps and showers without any pump. Designed for Economy 7 and off-peak tariffs, the TSC charges overnight and holds sufficient energy for a full day's domestic use. And because the immersion elements sit in static primary water that is never renewed, no scaling occurs — even in hard water areas — eliminating the annual maintenance obligation of unvented cylinders.
JAB EMU — Electric Multipoint Unit
Due for release by the end of 2026, the JAB EMU is a compact 10L and 15L electric multipoint water heater designed to supply hot water to single or multiple outlets — or even light commercial applications. Details are still being finalised, but the EMU will extend JAB's range into point-of-use territory, offering a British-made alternative in a category currently dominated by imported products. In the meantime, browse our existing instant and storage water heaters for point-of-use solutions available now.
JAB Duc Hi-Flo 400L & 500L — Built for High-Demand Environments
The Hi-Flo range is JAB's answer to the growing demand for large-capacity, high-recovery unvented cylinders in light commercial and large domestic settings. Launched in 2024 with 28mm inlets and oversized coils delivering 28kW on the 250L up to 38kW on the 500L, these cylinders are engineered for environments where hot water demand is relentless — multiple simultaneous outlets, back-to-back usage, and rapid recovery between peak periods.
Every indirect Hi-Flo model ships with 2 x 3kW backup immersion heaters as standard, 1" hot and cold connections, and a full unvented kit. The Duplex stainless steel construction provides the corrosion resistance needed for hard water areas and demanding commercial duty cycles. Available in both direct and indirect configurations from 250 to 500 litres. If you're pairing a commercial cylinder with a heating system, explore our electric boiler range or heat pump options for a complete solution.
Available Now at AIZO Quality Heating
JAB TSC 150L Direct E7 Man-Fill Thermal Store Cylinder
Open-vented thermal store delivering mains-pressure hot water via Economy 7 off-peak electricity. No discharge pipe, no G3 qualification, no annual maintenance. Specifically designed for new-build apartments where Building Regulations Part G prohibits unvented cylinder discharge into a soil stack.
£1,495.00 inc. VAT
£1,245.83 exc. VAT
JAB Cylinder Ranges at a Glance
| Range | Type | Capacities | Key Feature | Best For |
|---|---|---|---|---|
| Duc 2 | Unvented (External Expansion) | 90–500L | 22mm coils, slimline & horizontal options | Standard domestic replacement & new build |
| Duc IE | Unvented (Internal Expansion) | Various | No external expansion vessel, pre-plumbed options | Tight spaces, specification-led projects |
| Duc Hi-Flo | Unvented (High Recovery) | 250–500L | 28mm inlets, 28–38kW coils, 1" connections | Restaurants, salons, large homes, commercial |
| DOV | Vented (Open) | Various | 470mm wide, 1" connections, Duplex steel upgrade | Retro-fit from copper, low mains pressure areas |
| TSC | Thermal Store (Open Vented) | 150L, 180L, 210L | No discharge pipe, no G3, no annual maintenance | Apartments, restricted discharge properties |
| EMU | Electric Multipoint | 10L, 15L | Point-of-use electric water heater | Single/multiple outlets, light commercial (coming 2026) |
Choosing the Right JAB Cylinder
With six product families in the range, the right JAB cylinder depends on the property, the mains pressure situation, the installation constraints, and the hot water demand profile. Here is a quick decision framework to narrow it down — or use our water heaters buying guide for more detailed sizing advice.
Standard Domestic Home
The Duc 2 in direct or indirect configuration covers most domestic installations. Choose slimline or horizontal if the airing cupboard is tight. Add a solar twin coil if connecting to solar thermal.
Apartment or Flat
The TSC thermal store is purpose-built for apartments where Part G prohibits routing a discharge pipe into a soil stack. No G3 installer needed, no annual maintenance, and Economy 7 compatible.
Restaurant, Salon or Commercial
The Hi-Flo 400L or 500L delivers the high recovery rates and large storage volumes that commercial environments need. The 28mm inlet and up to 38kW coil output ensures rapid reheat between peaks.
Low Mains Pressure Property
The DOV vented range is designed for properties without adequate mains pressure for an unvented system. Built from Duplex stainless steel rather than copper, with 1" connections for maximum flow.
Frequently Asked Questions
What is Duplex stainless steel and why does JAB use it?
Duplex stainless steel is a two-phase microstructure combining austenitic and ferritic steel. It delivers roughly twice the yield strength of standard austenitic grades while offering superior resistance to stress corrosion cracking and pitting — particularly important in hot water cylinders where chloride exposure and thermal cycling are constant. JAB uses Duplex grade steel across all product families, with 316L grade stainless steel for fittings and connections, providing a long-service-life cylinder that resists the corrosion issues that can shorten the life of lesser-grade alternatives.
Do I need a G3-qualified installer for all JAB cylinders?
Only the unvented ranges (Duc 2, Duc IE, and Hi-Flo) require installation by a G3-qualified engineer under Part G of the Building Regulations. The JAB DOV is a vented cylinder and does not fall under G3 requirements. The JAB TSC thermal store, despite delivering mains-pressure hot water, operates as an open-vented atmospheric-pressure vessel — so it also does not require G3 certification. However, all installations should be carried out by a competent plumber in accordance with the relevant Building Regulations and manufacturer instructions. For more on ongoing servicing obligations, see our guide on how to service unvented hot water cylinders.
What makes the Hi-Flo range suitable for commercial use?
The Hi-Flo range is specifically designed for environments with sustained, high-volume hot water demand. Three features set it apart from standard domestic cylinders: the 28mm inlet valve allows higher incoming flow rates, the oversized coils (28kW on the 250L rising to 38kW on the 500L) enable rapid reheat between peak usage periods, and the 1" hot and cold connections ensure the pipework can deliver the flow rates that commercial taps and basins require. The indirect models also ship with 2 x 3kW immersion heaters as standard backup.
Why would I choose the TSC thermal store over an unvented cylinder?
The primary reason is installation constraints. In apartment buildings and properties where Building Regulations Part G prohibits routing a discharge pipe from an unvented cylinder into a soil stack, the TSC provides an alternative that still delivers mains-pressure hot water. Because it operates at atmospheric pressure, it needs no discharge pipe, no T&P relief valve, and no G3-qualified installer. It also requires no annual maintenance — the immersion elements sit in static primary water that is never renewed, so no scaling occurs even in hard water areas. The trade-off is that the TSC is an electrically heated thermal store optimised for Economy 7 tariffs, so it is not suitable for boiler or heat pump connections.
Are JAB cylinder spares readily available?
Yes. JAB works in partnership with specialist spare-part providers to ensure that thermostats, immersion heaters, safety valves, and other serviceable components are held in stock and available for fast dispatch. This is an important consideration for installers and maintenance engineers who need to keep cylinders operational over long service lives — particularly in managed property portfolios and social housing where rapid turnaround on repairs is critical.
Need Help Choosing a JAB Cylinder?
Our team can help you match the right JAB product to your project — whether it's a single domestic replacement or a multi-unit apartment specification. Request a custom quote for larger orders.