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Unvented Hot Water Cylinders
Discover the comprehensive range of WRAS approved and G3 Building Regulations compliant unvented hot water cylinders from World Heat Cylinders. We proudly manufacture every unit in our purpose-built Manchester facility. Making cylinders since 1989 (World Heat since 2008), we design, weld and test every cylinder in our own factories. This provides powerful mains pressure hot water for both domestic and commercial applications.
Meeting Diverse System Demands
Our standard unvented cylinders operate efficiently at a working pressure of 3 bar gauge. However, as specialist manufacturers, we can also produce unvented hot water cylinders for higher working pressures. For instance, we offer units rated for 4 bar, 5 bar, 6 bar, or even higher if your specific project demands it. This flexibility allows us to cater to a wide variety of system requirements and site conditions effectively.
A Comprehensive Unvented Cylinder Portfolio
The World Heat Cylinders unvented cylinder portfolio encompasses a diverse selection. This includes our high-performance Stainless SuperFlow range and versatile Twin Coil SuperFlow options for multiple heat sources. Additionally, we offer energy-efficient ClimaCyl Heat Pump cylinders. For space-saving needs, explore our EcoSlim, Ultra Slim, and Horizontal Unvented models. We also provide dedicated Pre-Plumbed systems and a full suite of Unvented Components.
The Advantages of Unvented Hot Water Systems
Unvented hot water systems are renowned for delivering excellent water pressure to all outlets. This makes them ideal for properties with multiple bathrooms or high-performance showers. Unlike traditional vented systems, they take their water supply directly from the mains. This direct feed eliminates the need for a cold water storage cistern in the loft and often simplifies pipework. As a result, it ensures consistently strong flow rates. Furthermore, because the system is sealed, the risk of contamination reduces. The system can also often be sited more flexibly within a property. World Heat Cylinders' expertise in unvented technology means we design every unit not only for performance and compliance but also for ease of installation and long-term reliability. Our commitment to using high-grade materials, like Duplex stainless steel, further enhances the durability and lifespan of our unvented hot water cylinders. This provides excellent value and peace of mind for both installers and end-users.
To explore detailed information on each of our unvented cylinder ranges, please select from the options below.
The range
All unvented cylinders
Direct Unvented Cylinder
Standard upright direct cylinder90–300 LView product
Direct Unvented Slimline
Slimline upright direct cylinder90–300 LView product
Direct Unvented Horizontal
Horizontal direct cylinder120–500 LView product
Indirect Unvented Cylinder
Standard upright indirect cylinder90–300 LView product
Indirect Unvented Slimline
Slimline upright indirect cylinder90–300 LView product
Indirect Unvented Horizontal
Horizontal indirect cylinder120–500 LView product
Ultra Slim Direct / Indirect
Ultra slim 400mm direct/indirect type60–120 LView product
Unvented Safety Kit
Inlet control group, expansion vessel, T&P valve and tundish supplied with every unvented cylinderView product
SuperFlow Twin Coil
Twin coil (boiler and solar) stainless steel unvented cylinder, 550mm diameter, 150L to 300L60–500 LView product
SuperFlow Twin Coil Slimline
Twin coil (boiler and solar) stainless steel unvented cylinder, 475mm diameter, 150L to 210L60–500 LView product
ClimaCyl
Heat pump coil cylinder120–500 LView product
EcoSlim
Slim heat pump coil cylinder90–210 LView product
Twin Coil Heat Pump / Solar
Twin coil cylinder with heat pump and solar coil60–500 LView product
SolarSolar Unvented Cylinder
Solar cylinder standard/slim/horizontal150–300 LView product
Help choosing and specifying
Guides and tools
- Find a cylinderThree questions: heat source, size and the space you have
- Will it fit? Cylinder space checkerEvery cylinder that fits your cupboard or plant space
- Replace an existing cylinderThe World Heat equivalent of the cylinder there now
- Legionella and safe hot water storageHSE L8 and HSG274 temperatures for stored hot water
- Building regulations for cylinders and heat pumpsPart L, Part G and Part P, with the 2026 Part L dates
Need this tailored to your project or system?
Different connections, coil, size, controls or finish: our design team builds to your requirements.
We also build own-brand ranges for OEM partners.
Need a cylinder built to your specification?
From 10 litres to 10,000 litres, our Manchester team designs, manufactures and tests every vessel in-house. We confirm and respond to every bespoke enquiry within 48 hours, and standard range enquiries immediately. If you need a price on a standard product, don’t hesitate to call and speak to one of our team on 0161 343 8610.We confirm and respond to every bespoke enquiry within 48 hours, and standard range enquiries immediately. If you need a price on a standard product, don’t hesitate to call and speak to one of our team on 0161 343 8610.We confirm and respond to every bespoke enquiry within 48 hours, and standard range enquiries immediately. If you need a price on a standard product, don’t hesitate to call and speak to one of our team on 0161 343 8610.