The JAB DUC 2 Horizontal range is an unvented stainless-steel hot water storage cylinder designed to lie on its side rather than stand upright, making it the practical choice for loft conversions and installations where ceiling or cupboard height is restricted. Available in six capacities from 125L to 300L, every size is built from duplex stainless-steel with a 316L-grade internal coil, heated indirectly from a gas or oil-fired boiler and backed up by twin factory-fitted 3kW immersion heaters that can also run the cylinder standalone on non-boiler-fed installations. The full range is manufactured in Britain.
2 x 3kW
Back-Up Immersion
7 bar / 90°C
T&P Relief Setting
316L
Coil & Fittings Grade
Lifetime*
Inner Vessel Warranty
Mounting cradles and the full unvented installation kit are supplied as standard on every size, and the remote expansion vessel ships with its own wall-mounting bracket, keeping each cylinder's own footprint as compact as possible.
Mounting orientation is safety-critical: every size in this range must be installed horizontally on the supplied cradles with all pipework connections uppermost. It must not be stood on end or rotated along its long axis, and installation must be carried out by a G3-qualified (Benchmark) installer and notified to Building Control under Part G3.
Footprint note: the length and diameter figures in the size table below are for the cylinder only on each model and exclude the remote expansion vessel, which is wall-mounted separately on its own bracket. Allow additional nearby wall space when planning the installation.
All electrical connections, including the twin immersion heaters, 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 Horizontal
Duplex Stainless-Steel Shell
The duplex stainless-steel body resists pitting and stress corrosion far better than standard 304-grade tanks, giving reliable long-term performance in hard-water areas.
Low-Height Horizontal Format
Lying the cylinder on its side rather than standing it vertically means it fits into restricted roof or cupboard heights where a standard upright cylinder simply won't stand, making it a common choice for loft conversions.
Dual-Purpose Immersion Back-Up
The factory-fitted 2 x 3kW immersion heaters aren't just boiler back-up – they let the cylinder run as a fully standalone electric water heater on installations with no boiler connection at all.
316L Coil & Fittings
The internal coil and compression fittings are 316L-grade stainless steel, chosen for its resistance to chloride pitting where the coil sees continuous wetted contact with boiler-circuit water.
Remote Expansion Vessel
The expansion vessel is supplied as a separate wall-mounted unit with its own bracket rather than clamped to the cylinder body, which keeps the horizontal footprint compact and eases future servicing access.
Cradles & Full Kit Included
Mounting cradles and the complete unvented kit are supplied as standard on every size, so the installer isn't left sourcing support brackets or safety-group components separately.
Sizes & Pricing
| Capacity |
Length (Cylinder Only) |
Diameter (Cylinder Only) |
| 125L |
900mm |
510mm |
| 150L |
1075mm |
510mm |
| 170L |
1200mm |
510mm |
| 200L |
1175mm |
555mm |
| 250L |
1500mm |
555mm |
| 300L |
1800mm |
555mm |
Technical Specification
| Construction |
| Cylinder Type |
Indirect, unvented, duplex stainless-steel, horizontal format |
| Coil & Fittings Grade |
316L stainless-steel |
| Manufacture |
Made in Britain |
| Capacities Available |
125L, 150L, 170L, 200L, 250L, 300L |
| Connections & Safety (All Sizes) |
| Fittings |
22mm compression, 316L stainless-steel |
| Temperature & Pressure Relief Valve |
Factory-set 7 bar / 90°C |
| Immersion Heater(s) |
2 x 3kW, factory-fitted (boiler back-up or standalone use) |
| Expansion Vessel |
Remote-mounted, wall bracket supplied |
| Mounting |
Supplied cradles required – connections uppermost |
| Unvented Kit |
Full kit supplied |
| Warranty |
| Inner Container |
Lifetime manufacturing warranty* |
| Components |
2 years* |
Frequently Asked Questions
Can this cylinder run without a boiler connection?
Yes, on every size in the range. The 2 x 3kW immersion heaters are factory-fitted for use on non-boiler-fed installations as well as boiler-fed ones, so the cylinder can operate as a standalone electric water heater.
How should the cylinder be mounted?
It must be mounted horizontally on the supplied cradles with the pipework connections uppermost, exactly as specified by JAB; it should not be installed standing on its end or rotated along its long axis, as this affects coil performance and venting of the safety group.
Do the quoted dimensions include the expansion vessel?
No. The length and diameter figures for each size are for the cylinder only. The expansion vessel is wall-mounted separately on its own bracket, so allow additional nearby wall space for it.
Does this cylinder need to be installed by a qualified installer?
Yes. As an unvented hot water cylinder it must be installed, commissioned, and notified to Building Control by a G3-qualified (Benchmark) installer in line with Building Regulations Part G3.
What heat source does the horizontal range use?
The internal coil is designed for a gas or oil-fired boiler as the main heat source, with the twin immersion heaters providing independent electric back-up or standalone operation, across all six capacities.
What warranty does JAB provide?
JAB horizontal cylinders carry a lifetime manufacturing warranty on the inner container (2 years on components); confirm the current warranty terms and registration process with JAB Products or your supplier at the time of purchase, as conditions may apply.
