LEGIONELLA - World Health Organization

Schedules for cleaning, disinfection and replacement
Treatment regimes should be validated to ensure that they can maintain control of microbial
growth under the worst case (highest bather load and throughput), and should be tested when
the pool is in use.
Frequent physical cleaning of hot tubs, as well as disinfection, is important because no disinfectant
can work efficiently if there is an accumulation of organic matter or biofilms in such areas as
the balance tank, strainers, filters and pipework. The whole system, including the balance tank,
should be cleaned at least once a week, and sand filters should be backwashed daily. While
advice about replacing the water varies, and depends to some extent on the amount of use, a
minimum of half the volume of water should be replaced each day (EWGLI, 2003). 12
Because of problems with rapid build-up of scale in many natural spa facilities, the main distribution
pipes are replaced every year. Chemical descaling of pipes is also possible, but is usually considered
less cost effective.
For whirlpool baths, it is advisable to disinfect the pipework regularly, while running the pumps
intermittently and using a biocide that is approved by the manufacturer as fit for the purpose
and that will not damage the surface. Designers should ensure that the system is completely
drainable, so that water does not stagnate between uses.
Keeping records
Disinfection, cleaning, operation, maintenance and servicing should be documented in appropriate
manuals, which must be integral parts of the risk assessment documents. All pool owners and
operators should have available:
• details of the person or people responsible for conducting the risk assessment and managing
and implementing the WSP, including their training portfolios
• drawings and updates that accurately describe the system, including any modifications
• operations manuals of manufacturers, suppliers and service providers
• standard operating procedures (e.g. for cleaning and disinfection)
• maintenance and service requirements
• shutdown procedures
• laboratory monitoring reports
• the dates and results of monitoring inspections, tests and checks
• the significant findings of the risk assessment and required remedial measures
12 http://www.ewgli.org/pdf_files/Guidelines_June_2003.pdf (accessed 12 July 2005)
LEGIONELLA AND THE PREVENTION OF LEGIONELLOSIS