Overview

The use of filtered clean rainwater collected from the roof (not general stormwater runoff) to fill spa pools and swimming pools is supported provided controls are in place to protect public health. Rainwater collected in tanks can be safely used for pools provided it is introduced into the pool through either the balance tank or into the pool at night to allow sufficient time for treatment before bathers enter the pool.

Safe rainwater use for swimming pools is achievable in most situations, unless rainwater is collected from roofs either constructed of hazardous materials (such as lead or preservative-treated timber) or located in heavily polluted areas where particulate pollution from vehicles, aircraft and industrial activities may contaminate rainwater.

Research indicates that first flush systems effectively minimise particulate and microbial pollution. First flush systems reduce contamination because the first few litres of rainwater, which contain the highest concentration of pollutants, are discarded to stormwater. Microbial contamination of rainwater can also be easily controlled by chlorination in the collection tank. The area of the roof needs to be considered when determining the quantity of first flush water to discard. The rainwater tank must be maintained and checked periodically for sludge accumulation.

Rainwater can have the added benefits of a low Total Dissolved Solids and is therefore soft water being low in carbonates. In heavily polluted areas, the cost of pre-treatment to maintain safe water may outweigh any benefits, especially where a reliable water source exists. Further information is contained in Rainwater Tanks (2) and Guidance on use of rainwater tanks.(3)

The use of filtered clean rainwater to top-up swimming pools is supported provided controls are in place to protect public health. A suggested risk assessment and management framework is outlined below.

Components to consider in water harvesting for use in swimming pools

(Developed for use with Australian Guidelines for Water Recycling: Managing Health and Environmental Risk (Phase 1), 2006(1)

Element 1: Commitment to responsible use and management of recycled water quality

Components

• Recycled water policy
• Regulatory and formal requirements
• Engaging stakeholder

Activity

• Regulatory framework compliance
  • Water Quality Guidelines:
    • NSW Health. Public Swimming Pool and Spa Pool Advisory Document 2012
    • Australian Drinking Water Guidelines
  • Health Risk Assessment Guidelines:
    • Australian Guidelines for Water Recycling: Managing Health and Environmental Risk (Phase 1), 2006
• Develop a recycled water policy

Element 2: Assessment of the recycled water system

Components

• Identify intended uses and source of recycled water
• Recycled water system analysis
• Hazard identification and risk assessment

Activity

• Source of water
  • Backwash from swimming pool(s)
• Treatment
  • Reverse osmosis
  • Ultrafine filtration (UFF) and/or granular activated carbon (GAC) may be recommended
• Intended uses
  • Recreational swimming
  • Hydrotherapy (possibly immunocompromised clients)
  • Learn to swim (infants not toilet trained)
• Exposure routes
  • Ingestion (100 mL) - more for infants
  • Dermal: disinfection by-product (DBP) - trihalomethanes (THM)
  • Inhalation: DBP - THM
• Assessment of water quality data
  • Turbidity, pH
  • Microbial quality
  • Chemical quality (DBP-THMs)
  • Water quality indicators: total dissolved solids (TDS) conductivity
• Treated backwash water to be tested prior to reuse
  • Microbial hazards
  • Chemical hazards
  • Hazards from failures
  • Control to prevent failures

Element 3: Preventive measures for recycled water management

Components

• Preventive measures and multiple barriers
• Critical control points

Activity

• Preventive measures
  • Control of bather hygiene, showers prior to pool entry
  • Treatment: best available technology (RO, UFF, GAC, ultraviolet [UV])
  • Validation of treatment system
  • Pipework purple with reuse caution and signage (may be needed)
  • Documentation of responsibilities, operational procedures
  • Backflow and cross connection prevention
  • Controls - monitoring, shutdown upon failure
• Communication
  • Recycled water should be tested prior to reuse, otherwise alternative clean water source should be used
  • Failures should be communicated and reported
  • Education program for operational staff
  • Validation prior to commissioning to ensure that recycled water complies with the standards for drinking water
  • On-line monitoring of pool water for TDS, free chlorine and/or oxidation-reduction potential (ORP)
  • Determine critical control points

Element 4: Operational procedures and process control

Activity

• Documented procedures
  • Operational monitoring (auditing of critical limits for TDS/conductivity)
  • A contingency plan should be developed to effectively deal with pool contamination events
  • Corrective active

Element 5: Verification of recycled water quality and environmental sustainability

Activity