GRP cold water storage tanks are subject to the Water Supply (Water Fittings) Regulations 1999, Building Regulations Approved Document G, BS EN 13280:2001, Kiwa certification requirements, and HSE ACOP L8 on Legionella control. In higher-risk buildings (18 metres or 7 storeys in England), the Building Safety Act 2022 additionally requires all safety-relevant tank information to form part of a digitally maintained golden thread from design through to occupation.
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01
GRP Cold Water Storage
Glass reinforced plastic (GRP) tanks store cold water within a building’s plumbing system, serving domestic hot and cold water demand or acting as a break tank feeding pressurisation equipment. They are available as one-piece moulded units, or as sectional (bolted panel) systems assembled on site — the latter common in larger buildings where access constraints prevent one-piece delivery.
GRP has largely replaced galvanised steel and asbestos cement tanks because it is corrosion-resistant, non-toxic, and can be manufactured to Kiwa-certified formulations suitable for potable water contact. A correctly installed and maintained GRP tank can achieve a service life of 25–30 years.
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Kiwa Certification
Kiwa is an internationally recognised certification, testing, and inspection body originating in the Netherlands. Founded in 1948 as the Keuring Instituut voor Waterleiding Artikelen (Testing Institute for Water Supply Articles), it now operates globally across water, energy, construction, and infrastructure sectors.
For cold water storage tanks and fittings, Kiwa certification confirms that materials are non-toxic, hygienic, durable, and compliant with potable water requirements. In UK practice, Kiwa approval (REG 4) is accepted as a recognised means of demonstrating compliance with the Water Fittings Regulations, alongside WRAS. Many GRP tanks carry both approvals to meet UK and international project requirements.
1948, Netherlands
Keuring Instituut voor Waterleiding Artikelen
Europe and international markets
Non-toxicity, hygiene, durability, traceability
Accepted for Water Fittings Regulations compliance
Certificates issued per batch for compliance records
Kiwa certification for cold water storage tanks covers safe, non-toxic GRP materials; structural durability under pressure and environmental loading; smooth, non-porous internal surfaces that limit bacterial growth; and batch testing with traceable certificates to support downstream compliance records.
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The Legal and Standards Landscape
Several instruments apply simultaneously. None supersedes the others; compliance requires meeting all of them.
Primary Legislation
Water Supply (Water Fittings) Regulations 1999
The principal legal instrument for cold water storage in England and Wales. Requires correct sizing, overflow arrangements, close-fitting lids, and advance notice to the water undertaker in many cases.
SI 1999/1148 — equivalent byelaws in Scotland and Northern Ireland
Building Regulations
Approved Document G — Sanitation, Hot Water Safety & Water Efficiency
Guidance under the Building Regulations 2010 on cold water supply, including adequate support for cisterns. Read alongside the Water Fittings Regulations and relevant British Standards.
2015 edition, updated 2016
Product Standard
BS EN 13280:2001 — GRP Cisterns for Cold Water Storage
Covers design, construction, performance, and testing of GRP tanks. Specifies minimum 25 mm foam insulation, grade 316 stainless steel internal fasteners, and thermal performance better than 0.06 W/m²/°C.
Compliance does not substitute for Kiwa certification
Material Certification
Kiwa Certification (REG 4)
Confirms the tank, materials, and fittings will not impair potable water quality. Internationally recognised. Accepted in UK practice alongside WRAS as a means of demonstrating compliance with the Water Fittings Regulations.
BS 6920 is the underlying UK material standard
Health & Safety
ACOP L8 & HSG274 Part 2 — Legionella Control
ACOP L8 (fourth edition, 2013) has special legal status. Requires risk assessment, written control scheme, stored water below 20°C, appointment of a responsible person, and records of all monitoring and inspections.
Legal basis: HSWA 1974; COSHH 2002; MHSWR 1999
Construction Safety
CDM Regulations 2015 — Health & Safety File
Requires a Health and Safety File at project completion, handed to the client. For a GRP installation this includes as-installed drawings, Kiwa certificates, structural loading, confined space information, and maintenance requirements.
SI 2015/51
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The Golden Thread of Information
The golden thread was given statutory effect by the Building Safety Act 2022 (Section 88), entering force on 1 October 2023. It is a digital record of all information needed to understand a building’s design, construction, and ongoing safety — created before construction begins, maintained throughout the building’s life, and kept accessible to those who need it.
Scope — Higher-Risk Buildings
The formal golden thread obligations apply to Higher-Risk Buildings (HRBs) — in England, residential buildings of at least 18 metres in height or 7 storeys. Below this threshold, the CDM Health and Safety File and ACOP L8 records remain legal requirements. The Construction Leadership Council recommends applying golden thread principles across all buildings.
Supporting Regulations
The Higher-Risk Buildings (Management of Safety Risks etc.) (England) Regulations 2023; the Higher-Risk Buildings (Keeping and Provision of Information etc.) (England) Regulations 2024; and the Building Regulations etc. (Amendment) (England) Regulations 2023 together specify what must be kept, by whom, and for how long across all phases of an HRB’s life.
Gateway 2
- Tank specification demonstrating BS EN 13280 compliance
- Kiwa certification documentation for tank and all fittings
- Structural calculations for support frame and floor loading
- Design confirming Water Fittings Regulations requirements (sizing, overflow, backflow)
- Legionella risk assessment at design stage
- Advance notification to water undertaker
Gateway 3
- As-installed drawings verified against design
- Manufacturer’s test certificates and declarations of conformity
- Commissioning record — initial fill, test, and sign-off within 10 days
- CDM Health and Safety File entries for the tank and plant room
- Record of any design changes affecting the tank specification
IN-Use
- Legionella written control scheme
- Tank inspection and cleaning records (minimum annual)
- Cold water temperature monitoring logs (below 20°C)
- Records of repairs, modifications, and component replacements
- Records of disinfection events and remedial chlorination
- Updated Legionella risk assessments following any system change
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Lifecycle Documentation Reference
The following table maps key documents to their legal basis across the full lifecycle of a GRP cold water storage installation.
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Stage
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Document
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Legal basis
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|---|---|---|
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DESIGN
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Tank specification — BS EN 13280, Kiwa certification, insulation
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BS EN 13280; Water Fittings Regs 1999
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|
DESIGN
|
Structural loading calculations for support
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Building Regulations; CDM 2015
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|
DESIGN
|
Backflow prevention design
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Water Fittings Regulations 1999
|
|
DESIGN
|
Legionella risk assessment (design stage)
|
ACOP L8; COSHH 2002
|
|
DESIGN
|
Advance notice to water undertaker
|
Water Fittings Regulations 1999
|
|
INSTALL
|
Kiwa certification certificates — tank and all fittings
|
Water Fittings Regulations 1999
|
|
INSTALL
|
Declaration of conformity to BS EN 13280
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BS EN 13280:2001
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|
INSTALL
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Commissioning record — fill, test, sign-off
|
ATCM guidance; ACOP L8
|
|
INSTALL
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As-installed drawings
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CDM 2015; Building Safety Act 2022
|
|
HANDOVER
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CDM Health and Safety File
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CDM Regulations 2015
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|
HANDOVER
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Golden thread package (HRBs only)
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Building Safety Act 2022; HRB Regs 2023/2024
|
|
OCCUPATION
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Legionella written control scheme
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ACOP L8; COSHH 2002
|
|
OCCUPATION
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Inspection and cleaning records
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ACOP L8; HSG274 Part 2
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|
OCCUPATION
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Temperature monitoring logs
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ACOP L8; HSG274 Part 2
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|
OCCUPATION
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Repair, modification, and replacement records
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BSA 2022 (HRBs); ACOP L8
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|
OCCUPATION
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Periodic Legionella risk assessment review
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ACOP L8
|
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Key Points for Duty Holders
Digital storage is mandatory for HRBs
The Building Safety Act 2022 requires golden thread information to be held in a secure digital system with version control, access management, and an audit trail. BIM platforms, document management systems, and cloud repositories are all used in practice.
Kiwa certificates must travel with the tank
A common failure at handover is the loss of Kiwa certification certificates and BS EN 13280 declarations. These must reference the specific tank serial number or batch and be included in both the CDM Health and Safety File and the golden thread.
Confined space requirements
Tanks of 1 metre depth or greater requiring entry for inspection or cleaning are subject to the Confined Spaces Regulations 1997. The risk assessment, permit-to-work procedure, and emergency arrangement must be documented and retained.
Legionella record retention
ACOP L8 does not specify a minimum retention period, but HSE guidance indicates records should be available for investigation or prosecution. A minimum of five years is widely adopted for inspection, monitoring, and cleaning records; risk assessments should be retained for the life of the system.
Design changes must be captured promptly
A tank upgrade, rerouted pipework, additional compartment, or change of fittings not recorded in the golden thread creates a documentation gap. The Building Safety Act 2022 requires that changes affecting safety-relevant information are updated promptly. The Accountable Person commits an offence if information is allowed to become materially out of date.
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FAQ
What is Kiwa certification and does it replace WRAS for UK projects?
Kiwa certification does not replace WRAS for UK projects — both are accepted means of demonstrating compliance with the Water Supply (Water Fittings) Regulations 1999, but WRAS remains the domestic UK scheme. Kiwa is an international body founded in the Netherlands in 1948 that tests products for potable water safety, hygiene, and durability. Its REG 4 approval is recognised across Europe and internationally.
Many GRP cold water storage tanks carry both approvals. Where only one is held, confirm with the relevant water undertaker that it is acceptable before installation.
Which buildings require a golden thread of information?
In England, the statutory golden thread obligations under the Building Safety Act 2022 apply to Higher-Risk Buildings (HRBs) — residential buildings of at least 18 metres in height or 7 storeys, whichever is reached first. The Building Safety Regulator (BSR), hosted within the HSE, acts as the building control authority for HRBs.
For all other buildings, CDM 2015 Health and Safety File obligations and ACOP L8 Legionella records remain legal requirements regardless of height. The Construction Leadership Council’s 2024 guidance recommends applying golden thread principles across the wider building stock.
Does BS EN 13280 compliance mean a GRP tank is approved for potable water use?
No. BS EN 13280:2001 covers structural design, construction, performance, and testing of GRP cisterns but does not verify that the materials are safe for contact with drinking water. Potable water suitability is confirmed by Kiwa REG 4 or WRAS approval, both of which test against BS 6920.
A compliant GRP cold water storage tank requires both BS EN 13280 conformity and a valid Kiwa or WRAS certificate. The absence of either creates a gap that a water undertaker or building control body may require to be closed before the installation is accepted.
How often must a GRP cold water storage tank be inspected?
At minimum, GRP cold water storage tanks should be inspected and cleaned annually. HSG274 Part 2 recommends this as a baseline. In higher-risk premises such as hospitals, care homes, and schools, more frequent inspection is required and should be specified in the Legionella written control scheme.
The specific frequency must be determined by the site Legionella risk assessment and documented under ACOP L8.
What temperature must cold water be stored at under ACOP L8?
Cold water must be stored and distributed at below 20°C. Under ACOP L8 and HSG274 Part 2, this is the threshold below which Legionella pneumophila growth is inhibited. Between 20°C and 45°C, the bacteria can proliferate.
In practice, GRP tanks must be insulated to a minimum of 25 mm (per BS EN 13280) and sited away from heat sources including hot pipework running in close proximity. Temperature at sentinel outlets must be verified and recorded as part of the monitoring programme.
Who is the Accountable Person under the Building Safety Act 2022?
The Accountable Person (AP) is the person or organisation holding a legal estate in the common areas of a higher-risk building or under a relevant repairing obligation for those areas — typically the freeholder or head leaseholder of a multi-occupied residential building.
The AP is responsible for maintaining the golden thread throughout occupation, including all safety-relevant records for building services such as cold water storage. An AP who allows golden thread information to become materially out of date commits an offence under the Building Safety Act 2022.
What information must be in the CDM Health and Safety File for a GRP tank installation?
The CDM 2015 Health and Safety File for a GRP cold water storage installation must include: as-installed drawings showing tank location, dimensions, and pipework connections; Kiwa certification certificates referenced to the specific tank batch or serial number; BS EN 13280 declaration of conformity; and structural loading information for the support frame.
It must also include: confined space assessment and entry procedure for the tank void where applicable; access arrangements; isolation and drainage procedures; and maintenance requirements including inspection frequency and component replacement schedule.
When must a Legionella risk assessment be reviewed?
Under ACOP L8, a Legionella risk assessment must be reviewed whenever there is reason to believe it may no longer be valid. Specific triggers include: changes to the water system; a change in building occupancy involving more susceptible persons; a notifiable case of Legionnaires’ disease linked to the premises; or a change in responsible person.
As good practice, review at intervals of no more than two years is widely recommended even without specific triggers, though this is not a statutory requirement.
Is advance notice to the water undertaker required before installing a cold water storage cistern?
Yes, in most cases. The Water Supply (Water Fittings) Regulations 1999 require advance notice to the local water undertaker before installing a cistern — unless it is a WC cistern or a cistern of no more than 1,000 litres supplying wholesome water for domestic purposes only. This covers most GRP cold water storage cisterns in commercial, residential, and institutional buildings.
Failure to notify where required is a criminal offence. The undertaker will typically require backflow protection as a condition of consent.
How long must Legionella and water system records be retained?
ACOP L8 does not specify a statutory minimum, but records must be kept long enough to be of use in any investigation or prosecution. In practice: inspection, monitoring, and cleaning records — minimum five years; Legionella risk assessments — for the life of the system, with superseded versions retained; disinfection and remedial action records — minimum five years.
For buildings within scope of the Building Safety Act 2022, records forming part of the golden thread must be retained and kept current for the life of the building.
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Principal References
Approved Document G — Sanitation, Hot Water Safety and Water Efficiency
MHCLG, 2015 (updated 2016)
BS EN 13280:2001 — GRP Cisterns for Cold Water Storage
BSI / CEN
Kiwa Certification for Water Tanks and Fittings
Tricel Water UK — Oct 2025 (updated Feb 2026)
ACOP L8: Legionnaires’ Disease — Control of Legionella Bacteria in Water Systems (4th ed.)
Health and Safety Executive, 2013
HSG274 Part 2: Hot and Cold Water Systems
Health and Safety Executive, 2014
Delivering the Golden Thread — Guidance for Dutyholders and Accountable Persons
Construction Leadership Council, August 2024
Golden Thread Master Document List
Building Safety Alliance
ATCM GRP Sectional Tank Specification
Association of Tank and Cistern Manufacturers
Cold Water Storage — Guidance for Installers and Consultants
Water Regulations Advisory Scheme (Water Regs UK)
CONTENTS
Free Download
Complete GRP Cold Water Tank Guide
Full lifecycle coverage — sizing, compliance, installation, Legionella control, and O&M schedules.
