Often Legionnaires Disease gets associated with cooling towers but there are other sources that are equally as hazardous and often overlooked.

Time from exposure to symptoms for Legionnaires’ Disease is typically between 2 and 10 days which can sometimes make it difficult to trace the source retrospectively.

Here are 11 potential sources of Legionella you should be aware of:

Hot Water Systems

Hot water storage should reach above 60℃ in order to kill Legionella bacteria. Often the bottom of the vessel can be under 60℃ but due to heat convection if temperatures range from 30℃ to 40℃ and heavy sludge has built up on the base of tank it creates ideal conditions for Legionella growth.

In some cases in order to increase energy efficiency, hot water systems are switched off or thermostats are intentionally turned down.

Warm water systems used in hospitals and aged care facilities reduce temperature and tend to be set around 42℃ and if feeding multiple outlets or an extensive system it’s advisable to have some form of systemic disinfection. The 2013 Legionella outbreak at Wesley hospital in Brisbane was a result of a warm water system and lead to a fatality.

Another consideration is solar hot water generation. They might need an electrical booster system because they may not consistently reach a temperature to eliminate Legionella.

On demand heaters are less affected as there is no tank and comes straight from town water.

Rainwater Tanks and Storage Tanks

The majority of rainwater is naturally relatively pure and free of chlorine and becomes excellent for bacteria growth. In summer Australian water temperatures can reach between 25 – 35℃. Often contamination from birds, leaf-litter, insects and rodents can find its way into the tank, accumulating sludge. Rainwater tanks can feed toilets and irrigation systems for gardens and are both capable of distributing aerosol. Also if feeding a pressure washer then further problems evolve.

Pools and Spa

Ongoing introduction of biological material, recirculated water and warm temperature (37℃) acts as an excellent breeding ground for bacteria. Bubbling and aerosol in close proximity to people makes it easy to inhale water vapour which means you don’t necessarily have to be in
the hot tub. Lots of pools and spas have extensive piping systems that creates large surface areas for bacteria to reproduce. Legionella may not be the only worry as Pseudomonas infections can be an issue on poorly maintained systems.

In 1999 in Bovenkarspel, Netherlands, a legionellosis outbreak killed 32 people and lead to 206 severe infections. It followed a manufacturer showcasing their hot tubs during a horticultural show. The victims happened to be passing by whilst the machines ran their cycles which had been filled up using a little used fire hose which leads onto the next risk.

Hose attachments

Rubber can biodegrade into nutrients for bacteria. When you add this to a little used water outlet and the summer temperatures, legionella can grow within biofilm on the inside of the hose. It dislodges and exits when the tap is turned on which is usually attached to something that generates spray.

One simple rule with detachable hoses, is for bacteria to grow you need water. If you hang up the garden hose and leave it to drain this will prevent biofilm growth.

Soil & Potting Mix

Legionella Longbeachae is a naturally occurring environmental organism which is commonly found in soil. A few preventative measures should be used when handling potting mix: wear a particulate disposable mask, let it settle, don’t shake the bag before use, dampen dry potting mix to prevent dust release, keep at arm’s length, wash down leftovers and brush away damp remains. A big majority of people who garden are over 50 which makes them statistically more vulnerable.

Nearby car/truck/boat washing facilities

There has been two proven cases: one in Beachlands, Auckland which was a rainwater fed yacht wash and a car wash at Hoppers Crossing, Victoria. In both cases the aerosol affected nearby residents. Car washing facilities are becoming more and more common. As a way of saving money they use water saving to capture and recycle water on site which is then recirculated, stored and often becomes warm through the process. Ideally the recirculated water should have a disinfection system fitted to ensure bacteria do not thrive.

Industrial Processes

An example of this is when plastic injection moulding plants use recycled water to cool lines. They can involve high pressure water that creates huge amounts of spray. If rusting metal comes into comes into contact with water it can provide a vital growth medium for Legionella. Temperatures can be an issue too as hot machinery and warm storage areas can increase the risk of bacteria growth.  

Hotels, Holiday and Retirement Villages

Many hotels go through times of low vacancy which present the issue of vacant rooms or perhaps there is particular area in lower demand such as deluxe facilities over standard rooms. If these areas remain vacant for long enough water quality can deteriorate quickly.
Retirement Villages suffer from the same vacancy issues as hotels but also the majority, if not all of their residents are over 50 and are vulnerable to Legionnaires’ Disease.

Misting systems

Horticultural or flower shops and grocery stores can have misting systems fitted to the display counter to make products look crisp and fresh. If drawn from non-potable sources the likelihood of legionella bacteria increases. They often have extensive networks of pipes and plenty of potential for deadlegs.

The long forgotten office shower

Perhaps it was put in during the favourable cycle-to-work-scheme, now the popularity has faded it has become a store room and maybe even a deadleg that could contaminate the entire water distribution system. You should always remember that offices can be potential sources of Legionella.

Ice Machines and Chilled Water

Legionella has been detected in high concentrations in ice machines.

A explanation of this could be looking at the process involved: tap water passes through an activated carbon filter removing chlorine residual from water, ice makers become hot due to the rear compressor and thermal crossover can occur on the incoming water allowing Legionella to multiply and although freezing makes legionella bacteria dormant it doesn’t kill them.

Severely ill patients are often given ice to rehydrate due to difficulty in swallowing water. These individual are very susceptible to legionella. Microaspiration can occur which is breathing in small amounts of water vapour as a result of consuming ice.

Remember an ice machine should be cleaned systematically at least yearly if not more regularly. Be aware that every component needs to be thoroughly sterilised.

Decorative Water Fountains

Out in the sun a fountain doesn’t take long for algae to form in the water and leaf matter to build up. These conditions allow bacteria to grow but more concerning is that fountains tend to be placed closely to entrances and even sometimes in reception areas. Many have spray nozzles which may look decorative but also produce water droplets which could be breathed in or enter into an open window. Bromine is the most common disinfectant used to keep them in a clean condition and they should be cleaned out every three months to keep the pond free of debris.

This is not an exhaustive list of potential risks but it highlights how different situations can present the risk of Legionnaires’ Disease.