ATAG iSteel Vented Cylinders
ATAG iSteel Vented Cylinders
The ATAG iSteel Vented Cylinder range are a modern, durable replacement for traditional copper hot water storage systems. These cylinders offer a solution for homes that require a vented setup while benefiting from the latest in cylinder design.
Available in both direct and indirect models, the iSteel vented range provides flexibility across a wide range of domestic applications. With sizes ranging from 85 to 260 litres, you can choose the capacity that best matches your home’s hot water needs. Whether you’re replacing an older cylinder or installing as part of a new heating system, there’s a size and model to suit your layout.
Each iSteel Vented Cylinder are made from high-grade stainless steel, offering a robust and reliable alternative to traditional copper units. Stainless steel construction ensures a long service life while reducing the risk of internal corrosion over time.
These cylinders are designed with convenience in mind. A built-in secondary return feature helps maximise hot water delivery, ensuring your system performs efficiently and meets household demand. The ‘C’ banding ErP rating demonstrates strong energy performance, helping to support lower energy consumption.
Installation is straightforward. Designed to meet the requirements of modern installers, iSteel Vented Cylinders are Part L compliant and engineered for ease of setup. That makes them a suitable fit for homes that want to upgrade without overcomplicating the process.
Every cylinder in this range is backed by a 10-year guarantee, offering added peace of mind and assurance of quality.
To explore available sizes and models or to speak with your local installer, contact an ATAG Selected Partner.


Key features and benefits
- Robust and reliable
- Built-in secondary return for maximum hot water deliver
- Efficient Erp ‘C’ banding
- Easy to install
- Part L compliant
- 10 year guarantee
Specification
The table represents the technical information for the cylinder part number.
Cylinder type | Actual size of vessel | Capacity | ERP Energy efficiency class | Part number |
ISTEEL VENTED INDIRECT CYLINDER 900 X 375 I | 845 X 445 | 85L | C | CY300085 |
ISTEEL VENTED INDIRECT CYLINDER 900 X 400 I | 816 X 470 | 98L | C | CY300098 |
ISTEEL VENTED INDIRECT CYLINDER 1050 X 400 I | 940 X 470 | 116L | C | CY300116 |
ISTEEL VENTED INDIRECT CYLINDER 900 X 450 I | 812 X 520 | 120L | C | CY300120 |
ISTEEL VENTED INDIRECT CYLINDER 1050 X 450 I | 937 X 520 | 144L | C | CY300144 |
ISTEEL VENTED INDIRECT CYLINDER 1200 X 375 I | 1149 X 445 | 116L | C | CY400116 |
ISTEEL VENTED INDIRECT CYLINDER 1200 X 450 I | 1060 X 520 | 166L | C | CY300166 |
ISTEEL VENTED INDIRECT CYLINDER 1500 X 450 I | 1360 X 520 | 210L | C | CY300210 |
ISTEEL VENTED INDIRECT CYLINDER 1800 X 450 I | 1614 X 520 | 260L | C | CY300260 |
ISTEEL VENTED DIRECT CYLINDER 900 X 375 D | 845 X 445 | 85L | C | CY100085 |
ISTEEL VENTED DIRECT CYLINDER 900 X 400 D | 816 X 470 | 98L | C | CY100098 |
ISTEEL VENTED DIRECT CYLINDER 1050 X 400 D | 940 X 470 | 116L | C | CY100116 |
ISTEEL VENTED DIRECT CYLINDER 900 X 450 D | 812 X 520 | 120L | C | CY100120 |
ISTEEL VENTED DIRECT CYLINDER 1050 X 450 D | 937 X 520 | 144L | C | CY100144 |
ISTEEL VENTED DIRECT CYLINDER 1200 X 375 D | 1149 X 445 | 116L | C | CY200116 |
ISTEEL VENTED DIRECT CYLINDER 1200 X 450 D | 1060 X 520 | 166L | C | CY100166 |
ISTEEL VENTED DIRECT CYLINDER 1500 X 450 D | 1360 X 520 | 210L | C | CY100210 |
ISTEEL VENTED DIRECT CYLINDER 1800 X 450 D | 1614 X 520 | 260L | C | CY100260 |

Not sure which boiler you need?
Our boiler finder will help you to choose the perfect boiler for your home.
Find your perfect boilerInstallers that you can depend on
From design through to installation and after-care service, our ATAG selected gas-safe installers are on hand to offer you excellent advice and the best solution possible that suits your needs.
Find an Installer