GRP Two-Part Water Tanks
Tricel manufactures GRP two-part water tanks — a cold water storage tank supplied in two horizontally split sections that are bolted together on site. Suitable for restricted access locations where a standard one-piece tank cannot fit. WRAS approved. Quick to assemble. Reusable and relocatable.
- •Supplied in two sections — upper and lower halves bolted together on sit
- •Suitable for restricted access where one-piece tanks cannot pass
- •WRAS approved under Regulation 4(1)a for potable cold water storage
- •272 to 5,690+ litres — insulated and uninsulated options
- •Can be disassembled and relocated — reusable for another application
- •UK manufacturer — Tricel Water UK, Weston-super-Mare and Lanark
Two-Part Tank - Key Specification
Split type
Horizontally split - upper & lower
Capacity range
272 to 5,690+ litres
Assembly
Bolt upper to lower on site
Approval
WRAS Reg. 4(1)a - potable water
GRP standard
BS EN 13280:2001
Insulation
Insulated & uninsulated options
Reusable
Yes - can be relocated
What is a GRP two-part water tank?
A GRP two-part water tank (also called a two-piece or horizontally split water tank) is a cold water storage tank manufactured in two sections — an upper half and a lower half — that are bolted together on site to form a complete tank. Two-part tanks are used where a standard one-piece tank of the equivalent capacity is too large or heavy to pass through the available access route, but full on-site sectional assembly is not required. They are WRAS approved for potable cold water storage under Regulation 4(1)a, comply with BS EN 13280:2001, and can be disassembled and relocated for another application. Tricel Water UK manufactures GRP two-part water tanks from 272 litres to in excess of 5,690 litres, available in insulated and uninsulated configurations for potable and non-potable cold water storage. Each tank is dispatched as a complete kit ready to assemble.
01
Definition
What Is a GRP Two-Part Water Tank?
A GRP two-part water tank is a cold water storage tank manufactured in two horizontally split sections — an upper half and a lower half. The two sections are bolted together at a flanged joint on site to form a complete, sealed tank. In use, the tank performs identically to a one-piece tank of equivalent capacity.
The purpose of the split is access. A standard one-piece GRP tank must pass through the available access route as a complete unit. For larger capacities, the complete moulded unit may be too large to navigate through a doorway, loft hatch, corridor or other restricted entry point. By splitting the tank into two halves, each section is smaller, lighter and easier to manoeuvre — both halves can be passed through access routes that would not accept the assembled tank.
Two-part tanks occupy a specific place in the product range between one-piece tanks and full sectional tanks. They cover the size range from approximately 272 to 5,690+ litres — volumes too large for a standard one-piece tank to fit through many access routes, but small enough that full on-site sectional assembly is not justified.
Also known as: Two-piece tanks • Horizontally split tanks • Split water storage tanks. All describe the same product. The defining characteristic is horizontal manufacture in upper and lower halves bolted at a central flange joint.
Two-Part Tank — How the split works
Upper section
Contains lid, hatch, overflow and float valve inlet. Approximately half the tank height.
———— Horizontal split joint - bolted flange ————
Lower section
Contains outlet, drain and base. Positioned first on the prepared base surface.
Result in use
Once assembled, the two-part tank functions as a single, sealed cold water storage vessel. The split joint is sealed by a gasket and clamped by the fixing bolts. Performance is equivalent to a one-piece tank of the same capacity.
02
Key Features
Key Features of GRP Two-Part Water Tanks
Two-part tanks combine the simplicity of one-piece tank construction with improved access flexibility. Six characteristics distinguish them from alternative tank types.
Restricted access solution
The upper and lower sections can be passed individually through access routes that would not accept the complete one-piece tank — including narrow doorways, loft hatches, tight corridors and restricted stairwells. Each half weighs significantly less than the complete unit.
Quick, straightforward assembly
Two-part tanks are described as one of the few quick assembly water storage solutions available. The lower section is positioned, the upper section placed on top and the joint is bolted. No specialist tools or trained installation teams are required beyond competent pipework connection.
Dispatched as a complete kit
Each tank is dispatched as a complete kit including both sections, fixing hardware, gasket material and all accessories. There are no items to source separately. The kit is compact in storage and straightforward to inventory before installation.
Reusable and relocatable
Unlike one-piece tanks, two-part tanks can be disassembled and relocated for another application. The upper and lower sections can be unbolted, moved separately and reassembled at a new location. This makes them well suited to temporary installations, rental applications and sites where future reconfiguration is likely.
WRAS approved for potable water
Tricel two-part tanks carry WRAS Regulation 4(1)a approval for potable cold water storage, confirming compliance with the Water Supply (Water Fittings) Regulations 1999 and suitability for systems connected to the public mains supply in the UK.
Compact in storage
The flat panel construction of the two sections means they take up significantly less storage space than a fully assembled round tank. This is advantageous for contractors holding stock for emergency response, temporary installations or projects with long lead times to installation.
03
Assembly Process
How a Two-Part Tank Is Assembled
Two-part tank assembly is straightforward. The process does not require specialist installation teams, confined space working or external scaffolding — it is designed to be completed by a competent installer working to Tricel’s assembly instructions.
Prepare the base
Prepare a flat, level and structurally capable base surface. The base must support the full water-loaded weight of the assembled tank and maintain the required flatness tolerance. An uneven base will create stress on the joint and may cause leakage.
Deliver sections to location
The lower section and upper section are transported individually to the installation position. Each half can pass through access routes that would not accept the assembled unit, including doorways, stairwells, loft hatches and corridor bends.
Position the lower section
The lower section is positioned on the prepared base in its final location, with outlet, drain and inlet connection positions confirmed against the pipework layout.
Place and bolt the upper section
The upper section is placed onto the lower section, aligning the horizontal flange joint. The joint gasket is seated and the fixing bolts are installed and torqued to specification. The bolted joint provides the structural connection and the sealed water boundary between the two halves.
Connect pipework and fittings
Float valve, inlet, outlet, overflow and drain pipework connections are made. The ball float valve is set to the correct water level. Screened vent and overflow positions are confirmed.
Clean, disinfect and commission
The assembled tank and associated pipework are cleaned, disinfected and flushed to BS 8558:2015 before being filled and placed into service. Retain installation records and WRAS documentation as part of the building asset file.
Time to assemble
Faster than one-piece for restricted access
For a straightforward installation with clear access to the final position, two competent installers can typically assemble a two-part tank in under half a day. The absence of multiple panels, complex panel sequencing or confined space working makes the two-part configuration faster than sectional assembly for the same capacity range.
Clean, disinfect and flush the completed installation before placing it into service for potable water storage. Retain the WRAS certificate and commissioning records as part of the building’s asset documentation and Legionella risk assessment evidence.
Tricel can advise on appropriate base preparation, connection positions and assembly sequence for each specific tank size. Contact technical sales before installation if the base condition is uncertain.
04
Applications
Where GRP Two-Part Tanks Are Used
Two-part tanks are used wherever a complete one-piece tank cannot fit through the available access route but sectional assembly is not necessary. The following applications represent the most common use cases.
Healthcare & NHS
Hospitality & Leisure
Infrastructure & Utilities
Fire Protection
High-Rise & Multi-Storey
Industrial & Manufacturing
Education
Agriculture
Food & Beverage
Local Authority & Public
05
Tank Selection Guide
One-Piece, Two-Part or Sectional? Choosing the Right Tank
The correct tank type is determined by three factors: required storage capacity, access route dimensions, and whether future relocation is needed. Follow this decision guide to identify the most appropriate Tricel product for your project.
Can the complete one-piece tank (assembled) fit through the available access route?
Measure the access route — doorways, stairwells, corridors — and compare against the external dimensions of the one-piece tank at the required capacity. Include height, width and any cornering space needed.
Can both halves of a two-part tank at the required capacity fit through the access route individually?
Each half is approximately half the height of the complete tank and significantly lighter. If both halves can be manoeuvred to the installation position separately and the required capacity falls within the 272–5,690+ litre range, a two-part tank is the most straightforward solution.
Progressive side panel assembly from inside the tank
Is the plant room perimeter clearance sufficient for EFB or IFB sectional assembly (~500mm all sides)?
|
Factor
|
One-Piece
|
Two-Part
|
Sectional
|
|---|---|---|---|
|
Capacity
|
45–16,000L
|
272–5,690+L
|
1,000L–4M+L
|
|
Access needed
|
Full tank as one unit
|
Upper and lower halves individually
|
Individual 1m panels
|
|
On-site assembly
|
None
|
Bolt 2 halves
|
Full panel build
|
|
Assembly time
|
Delivery & connect
|
Hours
|
Days (by size)
|
|
Reusable / relocatable
|
If access allows
|
Yes
|
Panels reusable
|
|
WRAS approved
|
Yes
|
Yes
|
Yes
|
|
Stock item
|
Selected sizes
|
Standard range
|
Custom design
|
If you are uncertain which tank type is appropriate for your project, contact Tricel technical sales with the access route dimensions, required capacity and installation location. Tricel can confirm the correct product within the range.
06
Technical Specification
GRP Two-Part Tank Technical Specification
Tricel two-part tanks are manufactured from the same GRP materials and to the same quality standards as the one-piece range. The following specifications apply as standard unless confirmed otherwise for the specific size and configuration.
|
Parameter
|
Specification
|
|---|---|
|
Tank construction
|
GRP — Glass Reinforced Plastic
|
|
Split configuration
|
Horizontally split — upper and lower halves
|
|
Joint type
|
Bolted horizontal flange with gasket seal
|
|
Capacity range
|
272 litres to in excess of 5,690 litres
|
|
Potable water approval
|
WRAS Regulation 4(1)a
|
|
GRP standard
|
BS EN 13280:2001 — GRP cold water storage
|
|
Water fittings regulations
|
Water Supply (Water Fittings) Regulations 1999
|
|
Insulation
|
Insulated (CFC-free PU foam) and uninsulated options available
|
|
Suitable for
|
Potable and non-potable cold water storage
|
|
Screened vent / overflow
|
Factory fitted — insect and debris screen
|
|
Float valve
|
Confirmed to inlet supply diameter at order
|
|
Reusable
|
Yes — can be disassembled and relocated
|
|
Kit despatch
|
Complete kit — both sections, hardware and accessories
|
|
Manufacturer
|
Tricel Water UK — UK manufacturer
|
Confirm the full size range and available configurations with Tricel technical sales at the time of enquiry, as available tank sizes may change. Not all capacities within the range may be in stock at all times.
Split type
Horizontal
Upper & lower sections
Capacity range
272–5,690+
Litres (confirm at order)
Approval
WRAS
Reg. 4(1)a — potable
Assembly
Bolt joint
No specialist tools
Insulated option
Cold water temperature maintenance
The insulated two-part tank incorporates CFC-free PU foam insulation to maintain stored water temperature and reduce the risk of heat gain from the surrounding environment. Required for potable water systems where the plant room temperature may cause stored water to approach or exceed 20°C — the threshold above which Legionella risk in cold water is elevated. Specify the insulated version as the default for potable cold water storage in heated or semi-heated plant rooms.
WRAS documentation
Available for O&M manuals and compliance files
WRAS approval documentation is available on request for inclusion in project O&M manuals, Legionella risk assessment files and water undertaker compliance records. Request the certificate reference at the time of order to ensure documentation is available for the project programme.
07
Technical Downloads
Two-Part Tank Technical Resources
Technical documents for M&E engineers, specifiers, installers and facilities managers.
Two-Part Tank Product Datasheet
Specification, capacity range, insulated and uninsulated options, assembly guidance and WRAS approval reference.
One Piece GRP Tank Product Brochure
Full range overview — insulated, uninsulated, Cat 5 and bespoke; capacity range and approvals.
Cold Water Tank Aftercare Brochure
Tricel and Hydraclean aftercare services — inspection, cleaning, chlorination and Legionella sampling for all GRP tank types.
08
Specification Support
TIF Tank Project Experience
Tricel two-part tanks are available in a standard range. Providing the required capacity, installation location and access route dimensions at the enquiry stage allows Tricel to confirm the most appropriate size and configuration quickly.
Information for a two-part tank quotation
Required storage capacity (litres)
Access route dimensions (narrowest point)
Insulated or uninsulated requirement
Outlet and drain connection positions
WRAS documentation required?
Relocation anticipated?
Installation location (internal or external)
Potable or non-potable duty
Inlet supply diameter (float valve size)
Base condition and surface type
Temporary or permanent installation?
Required delivery timescale
Request a two-part tank quote
Tricel’s technical sales team will confirm the appropriate two-part tank size, configuration and delivery options for your project.
If you are not certain whether a two-part tank or an alternative configuration is right for your project, Tricel can review the access route dimensions and required capacity and confirm the most suitable product.
09
Related Products & Resources
GRP Tank Range & Related Resources
Two-part tanks sit within Tricel’s full GRP cold water storage range. Find the right product for your access and capacity requirements below.
GRP Tank Range
Compliance & Aftercare
10
FAQs
GRP Two-Part Water Tank FAQs
Common questions from installers, M&E engineers, specifiers and facilities managers.
What is a two-part water tank?
A two-part water tank (also called a two-piece or horizontally split water tank) is a GRP cold water storage tank manufactured in two sections — an upper half and a lower half — that are bolted together on site to form a complete tank. Two-part tanks are used where a standard one-piece tank cannot pass through the available access route, but full sectional assembly is not required. Tricel manufactures WRAS-approved two-part tanks from 272 litres to in excess of 5,690 litres.
What is the difference between a two-part tank and a one-piece tank?
A one-piece GRP tank is moulded as a single complete unit and delivered ready to install — the access route must accommodate the complete tank. A two-part tank is made in upper and lower halves that are bolted together on site, so each half can pass through access routes the assembled tank cannot. Once assembled, both tanks perform equivalently.
What is the difference between a two-part tank and a sectional tank?
A two-part tank consists of two halves bolted together horizontally — it is simple to assemble and covers 272 to 5,690+ litres. A sectional tank is assembled from multiple individual 1,000 × 1,000mm GRP panels, covering 1,000 litres to over 4 million litres. Sectional tanks are used for large capacities or highly restricted access. Two-part tanks cover the intermediate range where one-piece access is not possible but full sectional assembly is unnecessary.
What sizes are GRP two-part tanks available in?
Tricel GRP two-part tanks are available from 272 litres to in excess of 5,690 litres. Both insulated and uninsulated versions are available. Confirm the exact size range and current availability with Tricel technical sales at the time of enquiry.
Are two-part tanks WRAS approved?
Yes. Tricel GRP two-part tanks carry WRAS Regulation 4(1)a approval for potable cold water storage. WRAS documentation is available for inclusion in project O&M manuals and compliance files. Confirm the approval status at the time of order for the specific size and configuration required.
Can a two-part tank be disassembled and relocated?
Yes. The upper and lower sections are bolted together and can be unbolted for removal. Both halves can then be transported to a new location through the same access routes used during the original installation. Two-part tanks are a practical choice for temporary installations, rental applications or projects where future relocation is anticipated.
When should I choose a two-part tank instead of a one-piece or sectional tank?
Choose a two-part tank when the required capacity is within the 272–5,690+ litre range and the access route cannot accommodate the complete one-piece tank, but sectional assembly is not required. Two-part tanks are well suited to loft installations, renovation projects, restricted plant rooms, emergency water storage and applications where future relocation is expected.
How long does it take to assemble a two-part tank?
Two-part tanks are designed for quick, straightforward assembly. Two competent installers can typically complete the assembly — positioning the lower section, placing and bolting the upper section, and connecting pipework — within a few hours for a standard size. Assembly time varies with tank size, access route complexity and base preparation requirements.
Should I choose insulated or uninsulated?
Specify the insulated version for potable cold water storage in heated or semi-heated locations where the ambient temperature could cause stored water to exceed 20°C. Cold water stored above 20°C increases Legionella risk and may breach the requirements of ACoP L8 and HSG274. The uninsulated version is suitable for external installations, plant rooms where ambient temperature is consistently low, or non-potable applications where water temperature control is not required.
UK GRP Tank Manufacturer
Specify a Tricel GRP two-part water tank
Send your required capacity, installation location, access route dimensions and insulation requirement. Tricel will confirm the right size and configuration and provide a quotation.
This product guide is provided for general guidance and information purposes only. It does not constitute engineering advice and should not be relied upon as the sole basis for design decisions. © 2026 Tricel Water. All rights reserved.
