The Vaillant uniSTOR PLUS Pre-Plumbed Heat Pump Cylinder is the internal-expansion, factory pre-plumbed variant of Vaillant's premium high-recovery cylinder range. Available in 150, 175, 210, 250 and 300 litres, every uniSTOR PLUS Pre-Plumbed model combines a factory-integrated internal "bubble top" expansion vessel with a pre-assembled connection panel — the tundish, three-way motorised valve and unvented cylinder kit are all factory-fitted — delivering the fastest and neatest possible installation. The internal vessel eliminates the need for a separate external expansion vessel entirely, making this the ideal choice for airing cupboards, utility rooms and compact plant rooms where every centimetre counts.
Built around Vaillant's large-diameter smooth-bore coil technology, the uniSTOR PLUS Pre-Plumbed delivers coil ratings up to 52.5 kW, with all connections front-facing and clearly labelled. Thermal-injected polyurethane insulation combined with vacuum panels keeps standby losses as low as 1.0 kWh/24 h, while the 100% recyclable stainless steel inner tank carries a 25-year anti-corrosion guarantee backed by a 2-year parts and labour warranty on all other components.
Internal
Expansion Vessel (Bubble Top)
25yr
Anti-Corrosion Guarantee
<5
GWP (Global Warming Potential)
85°C
Max DHW Operating Temp
⚠ 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. The internal expansion vessel pre-charge pressure must be checked and set to system design requirements during commissioning. All installations must be notified to Local Area Building Control or via a Competent Persons Scheme.
⚠ Compatibility, Sizing & Transport
The uniSTOR PLUS Pre-Plumbed is optimised for use with Vaillant heat pumps (aroTHERM plus, aroTHERM split, flexoTHERM). The 250 L and 300 L models feature an enlarged coil for compatibility with higher-output ground-source systems. Always verify sizing using the Vaillant cylinder compatibility matrix before specification. The cylinder must be installed in a dry, permanently frost-free room and must always be transported and stored vertically — laying the cylinder on its side risks damage to the internal expansion vessel.
ℹ uniSTOR PLUS vs uniSTOR PURE — Key Difference
The uniSTOR PLUS incorporates an internal "bubble top" expansion vessel, making the installation more compact with no external vessel or extra pipe connections required. The uniSTOR PURE uses an external expansion vessel (supplied) connected to an external port, offering flexibility in vessel positioning when plant room space allows. Both are available in pre-plumbed and standard (non-pre-plumbed) configurations. For installations where space is limited, the PLUS Pre-Plumbed delivers the smallest combined installation footprint of any cylinder in the range.
Key Features & Benefits
Internal Expansion Vessel — Maximum Space Saving
The defining feature of the PLUS range is the patented, factory-integrated internal "bubble top" expansion vessel. By housing the vessel within the cylinder body, there is no requirement for a separate external expansion vessel or additional pipe connections, producing the neatest possible installation footprint — essential for airing cupboards, utility rooms and confined plant rooms.
Factory Pre-Plumbed — Faster On-Site Installation
The tundish, three-way motorised valve and unvented cylinder kit are factory-installed before despatch. Front-facing, clearly labelled connections and a dedicated controls mounting plate are included as standard, allowing the installer to complete pipework connections quickly and confidently — saving hours on site and reducing the risk of commissioning errors.
Large-Diameter Smooth-Bore Coil
Vaillant's smooth-bore coil technology maximises heat exchanger surface area — up to 2.8 m² on the 300 L model — achieving coil ratings up to 52.5 kW for fast re-heat and efficient heat pump operation. The smooth-bore design inhibits limescale accumulation and promotes automatic de-scaling, maintaining efficiency over the full service life without chemical intervention.
Thermal-Injected PU + Vacuum Panel Insulation
Thermal-injected polyurethane insulation combined with vacuum panels achieves standby losses as low as 1.0 kWh/24 h — among the lowest in class. This superior insulation performance keeps stored water hot throughout the day, reducing unnecessary re-heat cycles and cutting running costs for the homeowner across the cylinder's full service life.
Factory-Fitted 3 kW Immersion Heater
A 3.0 kW factory-fitted immersion heater (13 A, 1.5 mm² cable) provides emergency backup hot water should the primary heat source be temporarily unavailable. The adjustable thermostat meets G3 unvented cylinder safety requirements and is set by the installer during commissioning. The element is accessible via the immersion heater boss on the cylinder body.
25-Year Guaranteed Stainless Steel Tank
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, giving installers and homeowners comprehensive long-term protection.
Low GWP & Sustainable Design
A Global Warming Potential of less than 5 and zero ozone depletion from the thermal-injected insulation, combined with a 100% recyclable stainless steel tank, makes the uniSTOR PLUS Pre-Plumbed one of the most environmentally responsible hot water cylinders available in the UK market.
Adjustable Feet & Automatic Air Vent
Adjustable levelling feet simplify installation on uneven surfaces, while the factory-fitted automatic air vent eliminates trapped air during commissioning without manual intervention. A pre-fitted drain valve is also included on the cylinder body, simplifying maintenance and annual servicing requirements.
Benchmark Compliant & HWA Member
Vaillant is a licensed Benchmark Scheme member and a full member of the Hot Water Association (HWA). The uniSTOR PLUS Pre-Plumbed carries CE and UKCA marking and meets EN 12897:2016. It is compatible with MCS-certified heat pump installations, supporting BUS grant-funded projects and Building Regulations compliance.
Variant Reference — uniSTOR PLUS Pre-Plumbed
| Capacity |
Vaillant MPN |
Model Code |
Energy Class |
Diameter (mm) |
| 150 L |
8000012320 |
VIH RW 150/5 B PPIAES |
B |
580 |
| 175 L |
8000012321 |
VIH RW 175/5 B PPIAES |
B |
580 |
| 210 L |
8000012322 |
VIH RW 210/5 B PPIAES |
B |
580 |
| 250 L |
8000012323 |
VIH RW 250/5 C PPIAES |
C |
580 |
| 300 L |
8000012324 |
VIH RW 300/5 C PPIAES |
C |
580 |
MPN source: Vaillant installation manual 8000014609-07 (July 2025). PPIAES = Pre-Plumbed, Internal (bubble top) expansion vessel, Immersion heater, Stainless steel. Note: MPNs 8000012315–8000012319 are the standard (non-pre-plumbed) PLUS cylinders — do not confuse with this pre-plumbed range.
Technical Specifications — PLUS Pre-Plumbed Range
| Specification |
150 L |
175 L |
210 L |
250 L |
300 L |
| Total Tank Capacity (L) |
~148 |
~175 |
~210 |
~249 |
~289 |
| Standby Losses (kWh/24h) |
~1.0 |
~1.1 |
~1.2 |
~1.4 |
~1.6 |
| Coil Rating (kW) |
~20.8 |
~24 |
~26 |
~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 |
| Expansion Vessel Type |
Internal "bubble top" — factory-integrated, no external vessel required |
| Max DHW Operating Temp (°C) |
85 |
| Max Heat Circuit Temp (°C) |
95 |
| Immersion Heater Rating (kW) |
3.0 (13 A, 1.5 mm² cable) |
| Outer Diameter with Insulation (mm) |
580 |
| Cold / Hot Water Connection |
¾" BSP female |
| Insulation Thickness (mm) |
50 |
| Standard Compliance |
EN 12897:2016 | CE & UKCA Marked | Benchmark Compliant | HWA Member |
* Capacities and coil ratings are indicative, based on equivalent PURE pre-plumbed and standard uniSTOR data. Always confirm final specifications with the current Vaillant uniSTOR PLUS technical documentation for your specific model prior to specification.
Frequently Asked Questions
What is the difference between the uniSTOR PLUS and uniSTOR PURE Pre-Plumbed?
The key difference is the expansion vessel arrangement. The uniSTOR PLUS Pre-Plumbed has a factory-integrated internal "bubble top" expansion vessel — no external vessel is needed, producing the most compact installation possible. The uniSTOR PURE Pre-Plumbed has an external expansion vessel (supplied) that is connected on site, offering more flexibility in vessel positioning but requiring a slightly larger installation footprint. Both are factory pre-plumbed with the tundish, three-way valve and unvented kit, and share the same stainless steel cylinder, coil technology and guarantee.
Is the uniSTOR PLUS Pre-Plumbed suitable for tight spaces such as airing cupboards?
Yes — this is specifically where the PLUS Pre-Plumbed excels. The integrated internal expansion vessel removes the need for any external vessel in the plant room, minimising the installation footprint. The pre-plumbed connection panel with front-facing ports further simplifies installation in confined spaces. All five capacities share the same 580 mm outer diameter; confirm the required height against available headroom for your chosen capacity.
Which Vaillant heat pumps are compatible with the uniSTOR PLUS Pre-Plumbed?
The uniSTOR PLUS Pre-Plumbed is designed to work with the full Vaillant domestic heat pump range, including the aroTHERM plus (3.5–12 kW), aroTHERM split (3.5–12 kW) and flexoTHERM ground-source heat pump (5–19 kW). The 250 L and 300 L models have an enlarged coil to support higher-output ground-source applications. Always consult the Vaillant cylinder compatibility matrix to confirm the correct model for the connected heat pump output.
What components are factory-fitted on the uniSTOR PLUS Pre-Plumbed?
The following are factory-installed before despatch: internal expansion vessel ("bubble top"), tundish, three-way motorised valve, unvented cylinder kit, automatic air vent, drain valve and 3.0 kW immersion heater. All connections are labelled and face forwards. A controls mounting plate is also included. The installer simply connects the heat pump pipework and domestic water supply to the clearly identified, pre-labelled ports.
What guarantee does the uniSTOR PLUS Pre-Plumbed 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, including the pre-plumbed assembly and internal expansion vessel. Full warranty coverage requires installation by a G3-qualified competent person, commissioning in line with the Benchmark Checklist, and annual inspection by a competent person. The Benchmark Checklist must be completed, signed and retained by the homeowner.
How do I select the right capacity uniSTOR PLUS Pre-Plumbed?
As a general guide: 150 L suits 1–2 bedroom homes with one bathroom; 175–210 L suits 3-bedroom homes with 1–2 bathrooms; 250 L suits larger 3–4 bedroom properties; 300 L is recommended for 4+ bedroom homes or high hot-water-demand properties. Always cross-reference with the connected heat pump output and number of occupants using the Vaillant cylinder compatibility matrix for your specific project.
