Unvented Hot Water Policy Summary

This policy outlines the maintenance requirements for unvented hot water storage systems in accordance with BS EN 806-5:2012. It ensures safety, Legionella control, and compliance through regular inspections, asset-specific reporting, and structured documentation accessible via the Log-Book Portal.

Document Version: 1.0
Last Reviewed: May 2025

Managing Unvented Hot Water Systems?

BS EN 806-5:2012 requires asset-specific inspection records. Our Log-Book Portal captures service history, system registers, and compliance data — all by system type and location.

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^†Modern unvented systems may include two means of temperature control (e.g. a two-port valve on the flow side and a three-way valve on the return) for additional safety and fine-tuned temperature regulation. This redundancy reduces the risk of overheating or Legionella proliferation by maintaining consistent thermal control.

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Unvented Hot Water Maintenance | BS EN 806-5:2012 Policy & Digital LogBook

Maintenance and Inspection of Unvented Hot Water Storage Systems – BS EN 806-5:2012

This policy supports the safe and compliant operation of unvented hot water storage systems in line with BS EN 806-5:2012.

In commercial premises, unvented hot water systems must be maintained to ensure:

System safety and efficiency
Legionella risk control
Legal and technical compliance

The systems operate under pressure and can pose significant safety risks if key safety mechanisms fail. As such, a preventative maintenance regime is necessary to fulfil statutory obligations under the Pressure Systems Safety Regulations (PSSR), the Health and Safety at Work Act, and industry best practice.

Typical Maintenance Tasks – Summary Scope

Task	Frequency	Purpose / Notes
Manual testing of T&PRVs	Every 6–12 months	Ensure clear discharge path and correct reseating of valves
Expansion vessel pressure check	Annually	Test and recharge/replace vessel if out of tolerance
Check non-return valves & pressure-reducing valves	Annually	Assess for blockages, seal wear and functionality
Drain and inspect cylinder	Annually	Flush out scale/sludge and visually inspect internal surfaces
Temperature monitoring^†	Monthly	Confirm cylinder storage ≥60°C; monitor return temps
Inspection of tundish & discharge pipework	Annually	Ensure unobstructed discharge and installation compliance
Descaling (as required)	Annually or by local water quality	Essential for systems in hard water areas
Test safety cut-out / overheat protection	Annually	Verify functional secondary temperature safety control

+ Material Comparison: Duplex Stainless Steel vs. Copper

Feature	Duplex Stainless Steel	Copper
Corrosion Resistance	Excellent – suitable for aggressive water conditions	Good – can degrade in soft/acidic water
Strength	High – allows thinner walls and higher pressure	Lower – requires thicker walls
Thermal Conductivity	Lower	Higher – quicker heat transfer
Longevity	20–30 years or more	10–15 years
Suitability for NHS	Excellent – HTM compliant, low-maintenance	Limited – not ideal for clinical estates

Documentation and Reporting

To demonstrate compliance, service providers or maintenance staff shall complete and retain the following:

Service report confirming all tasks completed and any defects noted
Temperature log (manual or BMS extract) to support Legionella control
Pressure readings for vessels and valves
Records of any parts replaced or further actions required
Photographic records of cylinder internals or damaged components (if applicable)

These records form part of the building’s statutory maintenance log and should be held for a minimum of five years, available upon request to inspectors or regulatory authorities.