Key Points
- Cold water storage tanks must be inspected at least annually under HSG274 Part 2 and BS8558.
- Six-monthly inspection is recommended for commercial and multi-residential buildings and supports earlier detection of risk factors.
- Inspection covers both the interior and exterior of the tank, access covers, fittings, insulation, and water temperature.
- Inspection is a distinct activity from a Legionella risk assessment — both are required under ACoP L8.
- All inspection findings and remedial actions must be recorded as part of the ACoP L8 compliance record.
The purpose of cold water storage tank inspection
Physical inspection of a cold water storage tank serves two purposes within the ACoP L8 framework: it is a control measure in its own right, and it provides information that supports the ongoing validity of the Legionella risk assessment.
As a control measure, inspection identifies deterioration in the tank structure or fittings, contamination of the water, breaches of the tank enclosure, insulation failures, and operational deficiencies — before these conditions escalate to a level where they present a material Legionella or water quality risk. Early identification allows remedial action to be taken on a planned basis rather than in response to an adverse sampling result.
As an information source, regular inspection records build a condition history for each tank. This history informs the risk assessment review, the appropriateness of the current cleaning and sampling regime, and any decisions about maintenance investment or tank replacement.
Regulatory basis
Cold water storage tank inspection is required as a control measure under the written scheme of control mandated by ACoP L8. HSG274 Part 2 specifies that CWSTs should be inspected at least annually. BS8558 provides additional procedural guidance. The Building Safety Act 2022 introduces documentation obligations for higher-risk residential buildings that make consistent inspection records particularly important.
Inspection frequency requirements
The minimum inspection frequency required under HSG274 Part 2 is annual. This is the baseline regulatory requirement for all commercial and multi-residential buildings in the UK. However, the same guidance recommends more frequent inspection where risk factors suggest it is appropriate, and a 6-monthly frequency is widely adopted for commercial buildings as standard good practice.
A 6-monthly frequency provides several practical benefits:
- Deterioration in tank condition — such as the onset of biofilm, minor sediment accumulation, or beginning insulation failure — is detected earlier, before it develops into a more significant problem requiring urgent intervention.
- The interval between inspections is aligned with the quarterly sampling programme, so that inspection findings and sample results can be reviewed together at least twice a year.
- Six-monthly records provide a richer condition history, which is of value when reviewing the risk assessment and when buildings change ownership or management.
- For buildings subject to the Building Safety Act 2022, more frequent documented inspections strengthen the evidence base held in the safety case.
The appropriate inspection frequency for a specific building should be defined in the written scheme of control, based on the Legionella risk assessment for that site. Buildings with elevated risk — including healthcare premises, buildings with vulnerable occupants, or systems known to have experienced previous sampling exceedances — may warrant a frequency higher than 6-monthly.
What a cold water storage tank inspection covers
A compliant inspection covers the exterior and interior of the tank, the associated fittings, and the water itself. The following checklist reflects the items Hydraclean’s hygienists assess during each inspection.
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Area
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Items checked
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Exterior structure
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Physical condition of tank walls, roof/lid, and base; signs of corrosion, impact damage, or structural movement; condition of supporting framework where applicable
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Access covers
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Presence and condition of access covers; integrity of seals and gaskets; correct fitting (covers must be close-fitting and not able to admit insects, birds, or other contaminants)
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Insulation
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Condition and continuity of insulation on the tank body and associated pipework; signs of damage, compression, or gaps that would allow heat gain and risk water temperature rising above 20 °C
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Overflow and warning pipes
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Correct positioning, screened termination (to prevent ingress), and adequate capacity; signs of staining or evidence of previous overflow indicating a float valve fault
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Float valve and inlet
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Correct operation of the float valve; water level at the correct set point; no evidence of short cycling or continuous flow; inlet screened or protected
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Outlet and distribution pipework
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Condition of outlet connections; signs of corrosion, leaks, or previous remedial work; presence of a vertical dead-leg below the outlet (which can harbour stagnant water)
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Tank interior and water
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Presence of sediment, biofilm, debris, scale, or other contamination; evidence of algae or mould growth; foreign bodies; colour or odour of water; condition of tank lining or coating; screen condition if fitted internally
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Water temperature
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Temperature recorded at point of access; cold water should be at or below 20 °C — temperatures above this increase Legionella risk
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Labelling
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Presence of appropriate identification labels on the tank and associated pipework, confirming contents and any relevant safety information
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What happens when a deficiency is found
When a deficiency is identified during inspection, the inspector records the finding in the inspection report and classifies it according to its potential risk. The report distinguishes between:
- Immediate action items — deficiencies that present a current and material risk, such as a missing access cover, a float valve that is allowing water to overflow, or evidence of significant contamination. These require urgent attention before the next scheduled visit.
- Planned maintenance items — deficiencies that do not present an immediate risk but should be addressed within a defined period, such as deteriorating insulation, minor corrosion, or a worn seal.
- Observations — items noted for monitoring that do not yet meet the threshold for remedial action, such as the first signs of minor scale or a slightly elevated sediment level.
All findings are uploaded to the client’s Watercompliance.online account. Clients can track each deficiency through the portal’s fault-tracking function, from identified through to resolved, with a dated audit trail. Hydraclean will advise on appropriate contractors or carry out remedial work where this falls within their scope of service.
Inspection versus risk assessment: understanding the difference
Inspection and risk assessment are both required under ACoP L8, but they serve distinct functions and should not be confused.
INSTECTION
CWST Inspection
- Physical check of tank condition and operation
- Carried out at defined intervals (at minimum annually)
- Identifies specific deficiencies requiring remedial action
- Records condition at a point in time
- Feeds into the risk assessment review process
- Carried out by a competent water hygiene technician
ASSESMENT
Legionella Risk Assessment
- Formal evaluation of the entire water system and its risk factors
- Defines the written scheme of control (what maintenance is required and how often)
- Identifies all risk factors, vulnerable populations, and control measures
- Requires review when conditions change (building use, occupancy, system modification)
- Must be carried out by a competent L8 risk assessor
- Produces a risk assessment report that should be kept and updated
In practice: the Legionella risk assessment defines the inspection frequency and scope; the inspection provides the evidence that the scheme of control is being implemented; and significant inspection findings trigger a review of the risk assessment.
Documentation requirements
ACoP L8 requires records of all inspection activity to be retained. A compliant inspection record includes:
- Date and time of inspection.
- Name and organisation of the person who carried out the inspection.
- The condition of the tank at the time of inspection, covering all items in the inspection scope.
- Water temperature recorded during the inspection.
- Any deficiencies identified, with a description of their nature and severity.
- Recommended corrective actions and the timescale for each.
- Reference to the previous inspection record, to allow condition trend monitoring.
- Where actions were taken or completed, a record of what was done and when.
Under the Tricel–Hydraclean aftercare package, all inspection records are produced by Hydraclean and uploaded to Watercompliance.online following each visit. Clients have direct access to the full inspection history for their site — available at any time, without contacting Hydraclean.
The Building Safety Act 2022 and inspection records
The Building Safety Act 2022 established the Principal Accountable Person (PAP) role for higher-risk residential buildings — defined as buildings of seven storeys or more (or 18 metres or more in height) containing at least two residential units.
The PAP must maintain a documented safety case, evidencing how building risks — including those arising from water systems — are being managed. The concept underlying this requirement is sometimes described as the “golden thread” of building information: a complete, accessible, and up-to-date record of the building’s safety management across its life.
Cold water storage tank inspection records held on Watercompliance.online contribute directly to this golden thread. They provide a dated, searchable, and auditable evidence base that Legionella control measures are being implemented as required by the written scheme of control. For buildings within the scope of the Building Safety Act, a digital compliance portal with direct client access is considerably more useful than a paper log book when evidence is required at short notice.
Frequently asked questions
How often must a cold water storage tank be inspected?
HSG274 Part 2 and BS8558 require cold water storage tanks to be inspected at a minimum annually. For commercial and multi-residential buildings, a 6-monthly frequency is recommended. The appropriate frequency for a specific building should be defined in the written scheme of control, based on the site’s Legionella risk assessment.
What does a cold water storage tank inspection cover?
A compliant inspection covers: exterior condition (structure, insulation, access covers, overflow and inlet arrangement); interior condition (sediment, biofilm, debris, lining, fittings); water temperature; float valve operation; overflow and warning pipe condition; inlet and outlet pipework; and labelling. All findings are recorded in an inspection report.
What is the difference between inspection and a Legionella risk assessment?
Inspection is a routine physical check of the tank’s condition carried out at defined intervals. A Legionella risk assessment is a formal, system-level evaluation that defines the control measures required (including inspection frequency and scope). Both are required under ACoP L8. The risk assessment defines what inspections should cover; inspection records feed back into the risk assessment review process.
What records must be kept for CWST inspections?
ACoP L8 requires records of: the date of inspection; the inspector’s name and organisation; the condition found; water temperature; deficiencies identified; recommended corrective actions; and subsequent actions taken. These records must be retained and be available for inspection by enforcement authorities on request.
What happens when a deficiency is found during inspection?
Deficiencies are classified by the inspector as immediate action items (requiring urgent attention), planned maintenance items (to be addressed within a defined period), or observations (items to be monitored). All findings are recorded in the inspection report and tracked through Watercompliance.online from identified to resolved.
Does the Building Safety Act 2022 affect CWST inspection requirements?
For higher-risk residential buildings (seven storeys or more, or 18 metres or more), the Building Safety Act 2022 requires the Principal Accountable Person to maintain evidence of building safety management. Consistent, dated CWST inspection records — particularly those held in a digital, auditable system such as Watercompliance.online — support compliance with this obligation and contribute to the building’s safety case.
CONTENTS
Tricel
Request 6-monthly inspection for your cold water storage tank
Contact Tricel Water UK to arrange the 6-monthly cold water storage tank inspection package, carried out by Hydraclean Ltd and documented on Watercompliance.online.
