Rainwater harvesting and greywater recycling systems are increasingly common in new and refurbished buildings across Ireland. They reduce mains water use by collecting rainwater or reusing lightly used water for things like toilet flushing, irrigation and vehicle washing. They are a good idea, but they introduce stored water that is not treated to drinking standards, so they need to be part of your legionella risk assessment.
Why these systems need attention
- Stored water. Water can sit in underground or roof tanks for days or weeks, especially in dry spells.
- Warmer temperatures. Tanks in sunny or enclosed locations can warm up in summer. Our post on warm weather and water systems explains why that matters.
- Organic matter. Leaves, dust and debris from roofs, or soaps and skin cells in greywater, provide nutrients for bacteria and biofilm.
- Spray. Uses such as irrigation sprinklers, hose washing and some toilet flushes can create fine droplets. Our guide to hoses, pressure washers and aerosols covers this.
Practical steps
- Include it in your legionella risk assessment. Make sure the assessor knows the system exists and how it is used.
- Follow the manufacturer’s maintenance schedule for filters, pumps, UV units or other treatment.
- Keep filters and tanks clean. Debris filters typically need regular checking and cleaning, and tanks need periodic inspection.
- Limit spray. Where possible, use drip irrigation rather than sprinklers, and avoid using harvested water for pressure washing near people.
- Label pipes and outlets. Non-potable water should be clearly marked so nobody drinks it or uses it for washing.
- Prevent cross-connection. The system must be properly separated from your drinking water supply. A competent plumber should confirm this.
- Manage quiet periods. If the building closes or demand drops, think about how stored water will be managed. See our reopening checklist.
- Keep records of maintenance and checks in your logbook.
The frequencies and methods above are typical practice and should be set for your system by your risk assessment and the manufacturer’s guidance.
Sampling
In some cases, sampling of harvested or recycled water may be useful to check that control measures are working. Your risk assessment will help decide whether that makes sense.
Your duties
Section 19 of the Safety, Health and Welfare at Work Act 2005 requires employers to identify hazards and assess risks. The HPSC National Guidelines for the Control of Legionellosis in Ireland (2009) give practical guidance on assessing and managing water systems.
Speak to us
Safer Solutions provides legionella risk assessments for all kinds of buildings, including those with water recycling systems, and sampling through an independent accredited laboratory. Call 086 275 9728, email info@safersolutions.ie or send us a message.