Ultraflow Horizontal Indirect Unvented Hot Water Cylinder 120L–500L

Duplex stainless steel offers superior corrosion resistance compared with standard 316L grades — a significant advantage in hard-water areas and wherever aggressive water chemistry could compromise a conventional cylinder over time. The material is specified for longevity, not just compliance, which is why Ultraflow can back it with a 25-year cylinder guarantee.

All horizontal cylinders are supplied with mounting cradles as standard. The cradles add 105mm to the installed height (i.e. the cylinder diameter plus cradle depth) and allow the cylinder to be secured safely on its side without the need for bespoke fabrication on site.

Every cylinder ships with a full high-quality unvented kit — including the pressure reducing valve, expansion vessel, inlet control set, tundish, T&P relief valve, and associated fittings — so the installer has everything needed to commission a G3-compliant installation straight from the box.

The large-surface-area primary coil ensures fast heat transfer from the boiler into stored water, minimising reheat time and reducing fuel consumption. Coil ratings range from 15.8kW (120L) up to 28.49kW (500L), delivering rapid recovery even during periods of high demand.

50mm of premium closed-cell foam insulation wraps the full body of every cylinder, minimising standing heat losses and keeping stored water at temperature for longer — translating directly into lower energy bills across the life of the product.

A high-quality 3kW Incoloy immersion heater is fitted as standard, providing a direct electric backup heat source independent of the boiler. Cylinders 150L and above are supplied with two immersion heaters for top-and-bottom flexibility and legionella control compliance.

A mechanical cylinder thermostat is included as standard, giving accurate temperature monitoring and control of the immersion heating circuit. This supports compliance with HSE legionella guidance on maintaining stored water at 60°C.

A secondary return connection is fitted as standard on 200L and above, enabling a secondary circulation loop for instant-hot-water performance across larger properties without the need for a modified cylinder or additional fitting.

All cylinders carry WRAS approval and are manufactured to BS EN 12897:2006 and 12897:2016, with full ErP energy labelling. Building Regulations compliance (Part L and G3) is verified by NSF Labs, making specification and sign-off straightforward for both installer and Building Control.

Ultraflow cylinders are manufactured in the UK and held in significant stock at distribution centres in Enfield and Northampton. Same-day or next-day despatch is available on most lines, minimising downtime on site and supporting fast-turnaround jobs.

Cylinders can be specified with optional upgrades on request: Highflow 1" hot and cold connections with 28mm inlet group, 6kW Incoloy immersion, 3kW or 6kW Titanium immersion elements, additional immersion heaters, and a larger capacity expansion vessel for high-volume systems.