Joule makes one of the widest cylinder ranges available in the UK, direct and indirect, in standard, slim and short bodies. Between them they cover 90 to 500 litres, so there is usually a model that fits both the demand and the cupboard.
Every cylinder is ErP rated, built from high-grade duplex stainless steel and supplied with 22mm compression fittings. Unvented cylinders require G3 qualified installation under Building Regulations Part G.
Browse the ranges below.
Joule Cyclone Air Cylinders
The Cyclone Air uses internal expansion, so there is no separate expansion vessel to find space for and the installation stays neat. That puts it in direct competition with the Megaflo, and it is worth comparing the two before committing.
The cold feed assembly arrives pre-plumbed, which cuts labour time on site, and the high-density polyurethane insulation keeps standing losses down. Certified by KIWA and Benchmark, and Joule is a member of the Hot Water Association.




Joule Cyclone Cylinders, Indirect
Heated by a boiler through an internal coil, with a backup immersion. Joule produces Short and Slim variants at almost every capacity, which is unusual and often the deciding factor when the airing cupboard will not take a standard body.
Grey outer casing over duplex stainless steel, with 316L internal components chosen for corrosion resistance at high temperature. Sized for anything from a small flat up to a large household, on the 22mm pipework found in standard domestic installations.
Joule Cyclone Cylinders, Direct
Electrically heated, with the same build as the indirect range and the same Short and Slim options.
The direct models take two immersions, which is the point worth understanding. One can run on an off-peak tariff such as Economy 7 and the other on peak, so most of the water is heated at the cheaper rate with the second element there for a shortfall. Set up properly, that is where the running cost saving comes from.
Flat-based for stability, lightweight, and every plumbing connection is labelled and reachable from the front. We supply the components needed to install from the point of purchase, to keep time on site down.


Short Cyclone Models
A reduced height where the ceiling or the cupboard is the constraint rather than the floor space. Same materials, same warranty, same build standard.








