🚿 Legionella Risk Assessment – Caban Heli

Location: Caban Heli, Plas Heli Cyf, Pwllheli
Assessment Date: October 2026
Assessed By: Stephen Tudor MRICS FNAEA MARLA for Plas Heli Cyf (Internal Competent Person)
Review Frequency: Annual or upon system change - After start of Sea Jay occupying Stiwdio Heli
Next Review Due: October 2027
Previous Assessment: December 2025 - see this link 

1. Executive Summary

This Legionella Risk Assessment covers the water systems within Caban Heli, a multi‑use building occupied by Derwen, Sea Jay Marine, and used occasionally by Plas Heli Events. The building has no cold water storage tanks, no dead legs, and uses instantaneous hot water systems in all daily‑use areas. A stored hot water system exists only for event showers, which are used infrequently and managed under a strict flushing and heating protocol.

The overall Legionella risk at Caban Heli is assessed as LOW, with appropriate control measures in place.

2. Building Description

Caban Heli is a mixed‑use building comprising:

• Educational areas used by Derwen
• Workshop/studio area used by Sea Jay Marine
• Event shower block (used only during large Plas Heli events)
• Circulation areas, toilets, and handwashing facilities
• Planned redevelopment into four commercial units

The building receives mains-fed cold water directly from the supply, with no cold water storage tanks.

3. Water System Overview

3.1 Cold Water System

• Cold water is supplied directly from the mains.
• No cold water storage tanks are present.
• Cold water feeds all taps in Derwen areas, Stiwdio Heli, and general circulation areas.
• No unused outlets or dead legs identified.

3.2 Hot Water Systems

Hot water is provided through three distinct systems:

A. Stiwdio Heli

• Heated by a gas combination boiler.
• Provides instantaneous hot water.
• No stored hot water.
• Very low Legionella risk.

B. Derwen Areas

• Heated by an electric flow heater.
• Instantaneous hot water only.
• No stored hot water.
• Very low Legionella risk.

C. Event Shower Block

• Heated by a stored hot water tank supplied by the main gas boiler.
• Used only during large Plas Heli events.
• System is normally off and isolated.
• Managed under a strict pre‑event protocol (see Section 7).

3.3 Future System Changes

The event shower block will be dismantled as part of the redevelopment into four commercial units, each with independent electric water heating systems. This will eliminate stored hot water from Caban Heli entirely.

4. Occupancy Profile

• Derwen: Daily use by staff and learners.
• Sea Jay Marine: Daily use of workshop area.
• Plas Heli Events: Occasional large events requiring shower facilities.
• General Public: Limited access depending on event type.

Occupancy patterns do not create elevated Legionella risk.

5. Hazard Identification

Potential Legionella hazards include:

• Stored hot water in the event shower tank.
• Shower heads capable of aerosol generation.
• Periods of non‑use in the event shower block.
• Temperature fluctuations if systems are not managed correctly.

No hazards identified in Derwen or Stiwdio Heli areas due to instantaneous systems.

6. Risk Evaluation

Using HSE L8 criteria:

Overall building risk: LOW.

7. Control Measures

7.1 Daily‑Use Areas (Derwen & Stiwdio Heli)

• Instantaneous hot water systems require no temperature storage monitoring.
• Taps used daily – no flushing required.
• No dead legs present.

7.2 Event Shower Block

Control measures include:

• System activated three days prior to an event.
• Water heated to ≥60°C in the cylinder.
• All shower heads flushed for at least 2 minutes.
• Temperature checks recorded.
• System turned off after the event.
• Shower heads cleaned/descaled annually.

7.3 General Controls

• Maintain hot water temperatures above 50°C at outlets.
• Maintain cold water below 20°C.
• Record flushing and temperature logs.
• Review RA annually or upon system change.

8. Monitoring Regime

Monthly

• Temperature checks at representative outlets.
• Visual inspection of event shower block (if in use).
• Record keeping.

Pre‑Event

• Activate stored hot water system.
• Heat water to ≥60°C.
• Flush all shower heads.
• Record temperatures and flushing.

Post‑Event

• Turn off stored hot water system.
• Flush showers.
• Record shutdown.

Annual

• Full RA review.
• Shower head cleaning/descaling.
• System inspection.

9. Schematic Description (Text‑Based)

Cold Water:
Mains → Direct feed → Taps (Derwen, Stiwdio Heli, circulation areas)

Hot Water (Derwen):
Electric flow heater → Instantaneous hot water → Taps

Hot Water (Stiwdio Heli):
Gas combi boiler → Instantaneous hot water → Taps

Event Showers:
Gas boiler → Stored hot water tank → Shower block → Shower heads

10. Future Changes

The event shower block will be removed during the conversion into four commercial units. Each unit will have independent electric water heating, eliminating stored hot water and further reducing Legionella risk.

The RA must be updated immediately once the redevelopment is complete.

11. Assessment Conclusion

Caban Heli presents a low Legionella risk due to:

• No cold water storage.
• Instantaneous hot water systems in daily‑use areas.
• Limited use of stored hot water.
• Strong pre‑event control measures.
• Planned removal of stored hot water systems.

Current control measures are appropriate and effective.

12. Assessor Declaration

I confirm that this Legionella Risk Assessment has been completed in accordance with:

• HSE Approved Code of Practice L8
• HSG274 Part 2 – Hot and Cold Water Systems

And reflects the water systems present at Caban Heli as of October 2026.

Assessor: Plas Heli Cyf

Stephen Tudor MRICS FNAEA MARLA

 for signed copy see attached 

Signature: __________________________

12th October 2026
Date: _______________________________