The Vaillant uniSTOR PURE Heat Pump Cylinder (standard, non-pre-plumbed) is a high-recovery, stainless steel unvented hot water cylinder that gives installers the freedom to connect and configure pipework to their own design. Available in 150, 175, 210, 250 and 300 litres, every standard uniSTOR PURE arrives complete with a tundish, three-way motorised valve, unvented cylinder kit, expansion vessel and a ¾" × 28mm MI-copper compression fitting. The 250 L and 300 L models also include a secondary return T-piece connection for properties with a secondary circulation loop.
Built around the same large-diameter smooth-bore coil technology as the pre-plumbed range, the standard uniSTOR PURE achieves standby losses as low as 1.0 kWh/24 h and coil ratings up to 52.5 kW, ensuring rapid re-heat and consistently high hot-water output when connected to a Vaillant air-source or ground-source heat pump. The 100% recyclable stainless steel inner tank carries a 25-year anti-corrosion guarantee, and the external expansion vessel (supplied) is connected during on-site installation to best suit the available space.
1.0
kWh/24h min. standby loss
25yr
Anti-Corrosion Guarantee
<5
GWP (Global Warming Potential)
B
Energy Efficiency Class (A+–F)
⚠ Installer Requirement
This is an unvented hot water cylinder. Installation, commissioning and servicing must be carried out exclusively by a G3-qualified competent person, in full compliance with Building Regulations (England & Wales) Part G and the Benchmark Commissioning Checklist. All installations must be notified to Local Area Building Control or via a Competent Persons Scheme. Annual inspection is required to maintain safety and warranty validity.
⚠ Compatibility & Sizing Note
The standard uniSTOR PURE is optimised for use with Vaillant heat pumps. The 250 L and 300 L models include a secondary return T-piece connection and have an enlarged coil for compatibility with ground-source systems with higher output. The cylinder must be installed in a dry, permanently frost-free location and must always be transported and stored vertically — never on its side.
ℹ Standard vs Pre-Plumbed
The standard (non-pre-plumbed) uniSTOR PURE is supplied with the tundish, three-way motorised valve, unvented cylinder kit, expansion vessel and compression fitting included but not factory-assembled. The installer connects and routes pipework during installation to suit the specific plant room layout. This approach is preferred where bespoke pipework routing is needed or where the pre-plumbed configuration does not suit the site layout. For a factory-fitted, faster-install option, see the uniSTOR PURE Pre-Plumbed.
Key Features & Benefits
Complete System Kit Supplied
The standard uniSTOR PURE is supplied with a tundish, three-way motorised valve, unvented cylinder kit, expansion vessel and ¾" × 28mm MI-copper compression fitting as standard. The 250 L and 300 L models additionally include a secondary return T-piece connection, supporting properties with a secondary circulation loop for instant hot water at all outlets.
Large-Diameter Smooth-Bore Coil
Vaillant's smooth-bore coil design maximises heat exchanger surface area (1.0 m² on 150 L, up to 2.8 m² on 300 L) for fast re-heat and efficient heat transfer from the connected heat pump. The smooth bore inhibits limescale formation and promotes automatic self-de-scaling, maintaining coil efficiency over the cylinder's full service life.
Class-Leading Standby Losses from 1.0 kWh/24 h
Thermal-injected polyurethane insulation combined with vacuum panels achieves standby losses as low as 1.0 kWh/24 h on the 150 L model — the lowest in class. This means stored hot water stays at temperature throughout the day, reducing unnecessary re-heat cycles and lowering the homeowner's energy bills.
External Expansion Vessel (PURE)
The PURE variant uses an external expansion vessel supplied with the cylinder. The installer connects and positions the vessel during installation to suit the site layout, with flexibility over whether it is mounted above or below the cylinder. Supplied expansion vessel sizes range from 12 L (150 L cylinder) to 25 L (250–300 L cylinders).
Factory-Fitted 3 kW Immersion Heater
A 3.0 kW factory-fitted immersion heater (13 A, 1.5 mm² cable, 1¼" BSP boss) provides emergency backup heating in case the primary heat source is unavailable. The immersion thermostat is adjustable during commissioning and meets G3 unvented cylinder safety requirements.
Recyclable Stainless Steel — 25-Year Guarantee
The inner cylinder is manufactured from high-grade 100% recyclable stainless steel with an ultra-hard-wearing outer shell. Vaillant backs this with a 25-year anti-corrosion guarantee on the tank and a 2-year parts and labour warranty on all other components, providing one of the most comprehensive guarantees available in the cylinder market.
Adjustable Feet for Flexible Siting
Adjustable levelling feet ensure the cylinder can be set plumb on uneven or sloped floors, avoiding stress on pipework connections. A pre-fitted drain valve on the cylinder body facilitates safe draining during servicing or when the property is left unoccupied in freezing conditions.
Low Environmental Impact
A GWP of less than 5 and zero ozone depletion from the thermal-injected insulation formulation, combined with a recyclable stainless steel body, makes the uniSTOR PURE one of the most environmentally conscious cylinders in the UK market. Suitable for specifiers targeting low-carbon heat pump system designs.
Benchmark Compliant & HWA Member
The uniSTOR PURE meets EN 12897:2016, carries CE and UKCA marking, and Vaillant is a full member of the Hot Water Association and a licensed Benchmark Scheme member. It is suitable for MCS-certified heat pump installations and BUS grant-funded projects.
Variant Reference — uniSTOR PURE Standard (Non-Pre-Plumbed)
| Capacity |
Vaillant Article No. (MPN) |
Model Code |
Energy Class |
Diameter (mm) |
Height (mm) |
| 150 L |
8000011512 |
VIH RW 150/5 B ES |
B |
595 |
1,000 |
| 175 L |
8000011513 |
VIH RW 175/5 B ES |
B |
595 |
~1,100 |
| 210 L |
8000011514 |
VIH RW 210/5 C ES |
C |
595 |
1,265 |
| 250 L |
8000011515 |
VIH RW 250/5 C ES |
C |
595 |
1,535 |
| 300 L |
8000011516 |
VIH RW 300/5 C ES |
C |
595 |
1,745 |
Technical Specifications — Standard PURE Range (Non-Pre-Plumbed)
| Specification |
150 L |
175 L |
210 L |
250 L |
300 L |
| Total Tank Capacity (L) |
148.6 |
~175 |
198.4 |
249.2 |
288.7 |
| Actual Capacity (no coil) (L) |
143.8 |
~168 |
190.7 |
236.3 |
273.5 |
| Hot Water Draw-Off (L) |
127.0 |
~152 |
172.5 |
211.0 |
230.9 |
| Standby Losses (kWh/24h) |
1.0 |
~1.1 |
1.2 |
1.4 |
1.6 |
| Reheat Time 70% (min) |
13.8 |
~14.2 |
14.6 |
10.6 |
7.5 |
| Coil Rating (kW) |
20.8 |
~24 |
26.0 |
40.7 |
52.5 |
| Heat Exchanger Surface (m²) |
1.0 |
~1.2 |
1.4 |
2.4 |
2.8 |
| Primary Flow Rate (L/h) |
900 |
900 |
900 |
900 |
1,300 |
| Heat Exchanger Pressure Drop (mbar) |
44 |
~70 |
100 |
170 |
200 |
| Max DHW Operating Temp (°C) |
85 |
| Max Heat Circuit Temp (°C) |
95 |
| Expansion Vessel (L, supplied) |
12 |
12–18 |
18 |
25 |
25 |
| Immersion Heater Rating (kW) |
3.0 (boss: 1¼" BSP female) |
| Outer Diameter with Insulation (mm) |
595 |
| Net Weight Empty (kg) |
38.0 |
~42 |
46.0 |
61.0 |
67.6 |
| Insulation Thickness (mm) |
50 |
| Standard Compliance |
EN 12897:2016 | CE & UKCA Marked | Benchmark Compliant | HWA Member |
* 175 L specifications are approximate, interpolated from the 150 L and 210 L verified data. Always confirm specifications with the current Vaillant technical documentation for your specific model before specification.
Frequently Asked Questions
What is the difference between the standard uniSTOR PURE and the pre-plumbed version?
The standard uniSTOR PURE is supplied with the tundish, three-way motorised valve, unvented cylinder kit and expansion vessel as loose components for the installer to connect and route on site. The pre-plumbed version has these components factory-fitted, with a pre-assembled connection panel that reduces installation time and the risk of errors. The standard model is preferred where bespoke pipework routing is required or where the pre-plumbed configuration does not suit the installation layout.
Is the standard uniSTOR PURE compatible with Vaillant heat pumps?
Yes. The standard uniSTOR PURE is specifically engineered to work with Vaillant heat pumps, including the aroTHERM plus, aroTHERM split and flexoTHERM ranges. The 250 L and 300 L models feature an enlarged coil for ground-source heat pump compatibility. Consult the Vaillant cylinder compatibility matrix to match the cylinder capacity to the heat pump output for optimum system performance.
What is included in the box with the standard uniSTOR PURE?
The standard uniSTOR PURE is supplied with: a tundish, a 28mm three-way motorised valve, a G3 unvented cylinder kit, an expansion vessel (sized to the cylinder capacity), and a ¾" × 28mm MI-copper compression fitting. The 250 L and 300 L models also include a secondary return T-piece connection. The cylinder's factory-fitted components include the immersion heater, T&P relief valve and drain valve.
What guarantee does the standard uniSTOR PURE carry?
Vaillant provides a 25-year anti-corrosion guarantee on the stainless steel inner tank and a 2-year parts and labour warranty on all other components. To retain full warranty coverage, the cylinder must be installed by a G3-qualified competent person, commissioned in accordance with the Benchmark Checklist, and inspected annually by a competent person.
Can the standard uniSTOR PURE be used with a secondary circulation loop?
Yes. The 250 L and 300 L models include a dedicated secondary return T-piece connection, making them suited to properties with a secondary circulation (seconday return) system for instant hot water at multiple outlets. The 150 L, 175 L and 210 L models do not include this connection as standard — an appropriate tee piece would need to be added during installation if required.
Which capacity uniSTOR PURE should I choose for my property?
As a general guide: 150 L is appropriate for 1–2 bedroom homes with one bathroom; 175–210 L suits 3-bedroom properties; 250 L is recommended for larger 3–4 bedroom homes; and 300 L suits 4+ bedroom properties or those with higher daily hot-water usage. Always cross-reference with the heat pump output, the number of occupants and the number of bathrooms, using the Vaillant compatibility matrix.
