OSO Slimline RI150 150L Indirect Unvented Cylinder

The OSO Slimline RI150 is the slimmest domestic unvented cylinder available at just 430 mm diameter, perfect for tight spaces while delivering powerful mains pressure hot water with rapid heat-up from its large smooth coil and NANOPUR + VIP insulation technology.

Key Features

• Ultra-slim 430 mm diameter – ideal for narrow cupboards and space-constrained installations.
• 150 litre indirect capacity with large 0.7 m² smooth scale-resistant coil for fast heating and high efficiency.
• NANOPUR foam + Vacuum Insulation Panels (VIP) reduce heat loss by up to 300 kWh/year for outstanding energy savings.
• ErP C-rated efficiency with low standing heat loss of just 76W / 1.82 kWh/24hrs.
• High-grade stainless steel tank with 25-year warranty and superior corrosion resistance.
• 3 kW immersion heater backup plus digital thermostats for reliable dual-heating operation.
• Factory-fitted G3 kit includes T&P valve, expansion vessel (12L), motorised valve, tundish and pressure controls.
• Compact height 1610 mm with wall stabilisation bracket for secure floor-mounted installation.

Why Buy the OSO Slimline RI150?

Designed specifically for tight installation spaces where standard 595 mm cylinders won't fit, the Slimline RI150 combines record-breaking slim dimensions with proven OSO quality engineering and energy efficiency.

Perfect for flats, extensions and refurbishments, this cylinder delivers high flow rate showers, fast recovery and long-term reliability backed by comprehensive safety features and a market-leading warranty.

Suitable For

• Space-restricted locations – narrow cupboards, flats, loft conversions and small properties.
• System boilers and regular boilers requiring indirect unvented hot water storage.
• Refurbishment projects upgrading from vented systems or replacing failed cylinders in tight spaces.
• Properties with hard water areas – smooth coil resists limescale buildup for longer life.

Technical Specifications

• Brand: OSO Hotwater
• Model: Slimline RI150 (Product code: 1326200)
• Type: Indirect unvented mains pressure hot water cylinder
• Capacity: 150 litres
• Energy Rating: C (ErP)
• Standing Heat Loss: 76W / 1.82 kWh/24hrs (EN12897)
• Dimensions: Ø430 mm x 1610 mm height
• Weight: 43 kg empty / 184 kg full
• Primary Coil: 0.7 m² smooth scale-resistant (HX)
• Heat-up Time (coil ΔT 55°C): 24.3 minutes
• Recovery Time (70% ΔT 55°C): 17 minutes
• Immersion Heater: 3 kW Incoloy (1 x 240V)
• Primary Flow Rate: 15 l/min @ 80°C
• Volume Mixed to 40°C: 221 litres
• Max Design Pressure: 6 bar
• Expansion Vessel: 12 litres
• Tank Material: 1.3 mm stainless steel
• Warranty: 25 years tank / 2 years components

Installation & Compliance

Supplied complete with all G3 unvented components including multibloc pressure reducing valve (3 bar), expansion relief valve (6 bar), T&P relief valve (90°C/10 bar), motorised valve and 12L expansion vessel with wall brackets for simple professional installation.