The JAB DOV Direct Vented cylinder is a stainless-steel replacement for traditional open-vented copper hot water cylinders, fed from a cold water storage cistern rather than mains pressure. Available in five capacities from 90L to 200L, each in a choice of Standard or Slim format, it's built from duplex stainless-steel and supplied with factory-fitted immersion heaters – twin 3kW elements on the 125L–200L sizes for multi-rate tariff flexibility. It is manufactured in Britain.
2
Formats: Standard / Slim
2 x 3kW*
Immersion (125–200L)
25 Years
Cylinder Warranty
This is a vented cylinder, not unvented: it must be fed by gravity from a cold water storage (feed and expansion) cistern, typically in the loft, with an open vent pipe terminating over that cistern. It does not use the mains-pressure unvented kit, T&P relief valve, or expansion vessel found on JAB's unvented ranges.
Installer requirement: installation must be carried out by a competent person in accordance with the Water Regulations and Building Regulations, including correct sizing and positioning of the feed and expansion cistern and vent pipe.
Immersion configuration varies by size: the 90L model has a single 3kW immersion, while 125L–200L models are fitted with 2 x 3kW immersions and thermostats as standard for multi-rate tariff use. Confirm the correct model when ordering.
All electrical connections, including the immersion heater(s), must be wired by a qualified electrician in accordance with BS 7671; actual cable sizing should be calculated on site rather than assumed from generic figures.
Why Choose the JAB DOV Direct Vented
Direct Replacement for Copper Cylinders
Sized and configured to replace old grade 1–3 copper cylinders directly, so existing airing-cupboard pipework and fixings can usually be reused.
Twin Immersion for Multi-Rate Tariffs
The 2 x 3kW immersion heaters and thermostats fitted to the 125–200L sizes let the cylinder heat water on separate schedules, making it well suited to Economy 7 and similar multi-rate electricity tariffs.
Compact Diameter
At 470–510mm diameter, the cylinder is no larger than a standard 450mm foamed copper cylinder, so it drops into existing airing cupboards without rebuilding the space.
Standard or Slim Format
Every capacity is available as a standard-diameter or slimline cylinder at the same price, so the format can be chosen to suit the available cupboard width rather than height.
Duplex Stainless-Steel Construction
The duplex stainless-steel body resists pitting and stress corrosion far better than the mild steel used in older copper-jacketed cylinders.
25-Year Cylinder Warranty
Backed by a 25-year warranty on the cylinder itself, reflecting the expected service life of the stainless-steel vessel.
Sizes, Formats
| Capacity |
Format |
Dimensions (H x D) |
Immersion |
| 90L |
Standard |
750 x 510mm |
1 x 3kW |
| 90L |
Slim |
900 x 470mm |
1 x 3kW |
| 125L |
Standard |
900 x 510mm |
2 x 3kW |
| 125L |
Slim |
1050 x 470mm |
2 x 3kW |
| 150L |
Standard |
1050 x 510mm |
2 x 3kW |
| 150L |
Slim |
1200 x 470mm |
2 x 3kW |
| 170L |
Standard |
1200 x 510mm |
2 x 3kW |
| 170L |
Slim |
1500 x 470mm |
2 x 3kW |
| 200L |
Standard |
1500 x 510mm |
2 x 3kW |
| 200L |
Slim |
1800 x 470mm |
2 x 3kW |
Technical Specification
| Construction |
| Cylinder Type |
Direct, vented (open-vented), duplex stainless-steel |
| Manufacture |
Made in Britain |
| Warranty |
25 years on the cylinder |
| Connections |
| Cold Feed |
1″ female iron (from feed & expansion cistern) |
| Hot Draw-Off |
1″ female iron |
| Secondary Return / Shower Connection |
1″ female iron |
| Electrical |
| Immersion Heaters (90L) |
1 x 3kW |
| Immersion Heaters (125L–200L) |
2 x 3kW with thermostats |
Frequently Asked Questions
Is this a vented or unvented cylinder?
This is a vented (open-vented) cylinder, fed by gravity from a cold water storage cistern rather than direct from the mains. It is not interchangeable with JAB's unvented ranges, which require a completely different installation kit and mains-pressure feed.
Do I need a cold water storage cistern to install this?
Yes. As a vented cylinder it must be fed from a cold water storage (feed and expansion) cistern, typically in the loft, with an open vent pipe terminating over that cistern.
What's the difference between the Standard and Slim format?
Both hold the same capacity and cost the same; the Standard format uses a wider, shorter shell while the Slim format is narrower and taller, so the choice comes down to which best fits the available airing-cupboard footprint.
Is the 90L model the same as the rest of the range electrically?
No. The 90L model has a single 3kW immersion heater, while all other capacities (125L–200L) are fitted with 2 x 3kW immersion heaters and thermostats as standard.
Can this be used on an Economy 7 tariff?
Yes, the twin-immersion 125L–200L models are specifically suited to Economy 7 and similar multi-rate tariffs, with each element able to be scheduled independently.
Does this cylinder need a temperature and pressure relief valve?
No. As a vented cylinder it relies on the open vent pipe over the feed and expansion cistern for pressure relief rather than a mechanical T&P valve, which is specific to unvented systems.
