There is a simple rule to follow when it comes to controlling Legionella in an Australian hot water system: make sure the stored water is sufficiently hot to put off any bacterial growth, yet you must govern the temperature at the point of delivery to preclude scalding. For guidance on Plumbing Code hot water limits, proper design of the system and its temperature controls will see to this, as will regular upkeep and, in higher risk situations, professional input.
For the average householder putting on a shower there is little thought given to Legionella. But the bacteria are capable of growing in warm, still water and finding their way into the lungs via a fine spray. Showers and spa outlets, cooling apparatus or a hot water service in want of maintenance can present just such an opening. What follows is a guide to sensible controls for the home, rental property or workplace in Australia, and for buildings where the risk is greater, with some hard-earned tips from Adelaide Crowe.
Where Legionella Grows
To have good control one has to be aware of what conditions Legionella is drawn to. An understanding of where warm water might sit and cool, or be deprived of its protective heat, makes for a maintenance plan that is not so enigmatic.
The bacteria are a natural part of certain water environments. It is the plumbing system that can let them get out of hand and multiply, especially if the water is warm and stagnant or shielded by biofilm and sediment. One is infected by inhaling an aerosol or fine droplets of contaminated water, not from drinking at the tap.
Warmth, Stagnation And Spray
Any water left in a range of temperature conducive to bacterial growth raises the risk. You will find warm pockets in long pipe runs, dead legs, unbalanced circulation or in the odd bathroom or shower outlet that does not see much use.
Showers are of concern for the aerosol they make. So too can a spa bath, a spray tap or some commercial systems. Weeks of disuse does not make a tap inherently hazardous but it should be flushed and looked over before being put to regular use.
People are apt to think a system that looks clean is safe. Do not be fooled; you cannot tell by sight, taste or smell if Legionella or biofilm are present. There may be scale and microbial build-up behind a shiny showerhead. Plumbing will conceal its issues in access panels and behind walls and ceilings.
Storage And Delivery Temperatures
Most hot water systems rely on temperature as the main line of defence, though storage and delivery are not the same thing. The vessel is there to stifle bacterial growth, the outlets to ward off burns.
You will often see hot water in Australia held at 60°C or more, a tempering or thermostatic device then bringing the fixture temperature down. State and territory rules, the National Construction Code and Australian Standards in their current edition will dictate the specifics for a given building and system.
If there is a scalding issue, do not remedy it by cranking the storage heater down to the low temperature of the tap. The burn risk at the outlet may be gone but you have made things easier for bacteria in the distribution and storage system.
The Case For Mixing Valves
Before reaching a fixture a tempering valve will combine the hot and cold. Where tighter control is called for a thermostatic mixing valve will be used to accommodate any change in temperature. They require to be put in, commissioned and maintained as they should be.
A valve that is not up to scratch or has been fiddled with will give you trouble of two kinds: an outlet that is dangerously hot, or one that is cooler than it ought to be with the storage temperature to match. A screwdriver is no substitute for sound maintenance.
Compliance is a matter of the Plumbing Code hot water limits but there is no universal setting across Australia. Obligations for an apartment block or hospital are not the same as for a family home or childcare service. A licensed plumber and the state or territory authority can put you right on the requirements.
Building Risk And Controls
The degree of monitoring required will vary. A large building with recirculation pumps and long pipe runs and residents more open to infection is a different proposition to a small household system in regular use.
| Setting | Main Concern | Useful Control |
|---|---|---|
| Ordinary household | Infrequent use of its outlets and shower aerosols, and they are not always well looked after | What is required is a temperature control device in good working order, correct storage temperatures and some regular outlet use |
| Rental property | The tenant is unlikely to be aware of the system’s history or where the isolation points are | Make for prompt repairs with clear reporting and have your maintenance on record |
| Apartment or commercial building | Long pipe runs, dead legs and plant that is shared | Put in place a plan for water management, do circulation checks and have it professionally commissioned |
| Aged care or healthcare | Complex systems and occupants who are vulnerable | Site-specific risk management, monitoring and specialist compliance advice |
| Childcare facility | Water hygiene and the danger of scalding | Ensure access is secure, test safety devices routinely and have a compliant form of temperature control |
Older people, smokers and those with a weakened immunity or conditions like diabetes, cancer, kidney or chronic lung disease are more likely to suffer from severe Legionnaires’ disease. An older person does not for that reason require a special plant room in the home, but any facility with a vulnerable population should regard water safety as part of their operations, not a plumbing exercise once in ten years.
A Written Water Plan
If the site is of a higher risk or size, one should put on paper the layout of the system, faults, corrective action taken and when maintenance was done. This includes outlet, storage and circulation temperatures and any pipework that has been changed or outlets that are not often used.
The plan should make plain what is to be done if a temperature is out of the norm, who is to contact the plumber, who can isolate the system and who is responsible for checking it. In the event of a fault there should be no question as to whether a shutdown, a warning sign or a service call is called for.
Public-health authorities are the source of guidance for outbreak response in the more risky settings. For information on the symptoms and prevention of Legionnaires’ disease, refer to NSW Health.
Outlets And Pipework
Neglect of the downstream pipework will erode the safety margin of even a properly set heater. Maintenance ought to be concerned with cleanliness, temperature and movement, and anything in the system that has become quietly redundant.
Make sure to run the odd tap or shower from time to time, especially in a property that has been unoccupied. When flushing, direct the outlet to a container or drain so as to limit any aerosol exposure and do not stand in the spray for the first flush after an extended period.
Scale on a hose or showerhead will impede flow and hold organic matter. The manufacturer will tell you how to go about cleaning or changing them. But if the fitting is badly scaled or in poor repair, it is better to replace it than put in a heroic effort to scrub it and hope it holds up.
Check The System
There are obvious warning signs a household check can turn up – an hot water system having trouble to recover, a valve leaking, corrosion, noise or an outlet left to itself – but this is no substitute for a professional to do the testing.
- Make certain the pump, valves, isolation points and heater are unobstructed.
- Have the type of system, date of installation and service history to hand.
- Leave the electrical and gas work, pipe alterations, disinfection and any adjustment of the valve to a licensed plumber.
- No chemicals or bleach should be put into a hot water system without a qualified professional saying the method is sound.
- Before putting a system back in use or servicing it, give the occupants a heads up.
An accurate thermometer is needed for temperature checks and the instructions of the maker of the system should be heeded. A single reading at a tap is not proof of safety across the board; in a large system the furthest outlet may be quite different from the return line or the storage vessel.
Faults And Illness
Not every temperature fault is an outbreak, but to overlook it is not an option. It is a maintenance issue: document it and get some competent counsel before any major move is made.
Should a hot water system be found to be contaminated, altered or out of its operating range, or has been shut down, a water-hygiene specialist or qualified plumber can determine if further investigation or component replacement is in order. Do not think of thermal disinfection as a weekend project; the very hot water involved is a scalding hazard.
- Where there is a legitimate hygiene worry, put restrictions on the use of the offending sprays or showers.
- Put the landlord, employer or building manager in the picture.
- Have a licensed plumber come and assess the situation.
- In the case of a suspected cluster or an illness, act on medical or public-health advice.
Respiratory symptoms of the sort seen with other chest infections, including fever, a cough, aches in the muscles, shortness of breath or a headache, can be indicative of Legionnaires’ disease. Those with risk factors would be well advised to see a doctor if they are troubled by such symptoms. A clinician is a better judge than the internet and the plumbing will not make a diagnosis.
Testing
In the course of an outbreak investigation or when dealing with healthcare, aged care and commercial premises, water sampling has its place. Yet one cannot take a negative result as assurance that Legionella is gone from the system for good; the bacteria are not always evenly spread and a sample is only indicative of what was there at the time and point of testing.
The resident in an ordinary home would be unwise to make routine Legionella sampling the first port of call for control. One gets better protection from sound temperature management, clean outlets and proper flow, to say nothing of prompt repairs and having an unusual system put through its paces by a professional. Testing ought to be in service of an answer, not an expensive exercise in theatre.
Common Control Mistakes
Bad intentions have little to do with most problems, they are more a matter of taking an understandable shortcut. The issue is you can move the risk about the system without it being apparent.
A case in point is the low-temperature continuous-flow unit put in on the supposition that the rest of the plumbing is of no consequence. Or the tempering valve given over to a less expensive replacement not fit for purpose. Then there is the vacant rental left to itself for months and then every shower is put on without a safe flush.
Some will conflate scald prevention and Legionella prevention. While related they are not the same thing. Scald prevention puts a cap on outlet temperature, Legionella control is a matter of managing the entire water system down to the pipework, storage and maintenance.
Reality is straightforward: a new heater does not amount to a water-management plan. It may be poorly commissioned or tied to old pipework with dead ends. Do not be fooled by a plant room that looks fresh, there can be old problems in there under a clean shirt.
Make The Right Next Move
Have a professional come and look at the condition of your system, the tempering equipment and storage and outlet temperatures. Put it to the plumber to tell you what he has measured and what standard is in play and what his recommendation is for the building.
Those running a hotel, workplace, apartment block, healthcare or aged-care facility should have a water-management process in writing with responsibilities spelt out. Should safety need to be improved in a day, focus on the showers, any system where temperature control is in doubt, and the bathrooms of vulnerable occupants.
Legionella control is not an affair of panic or sterile perfection. You want to maintain fittings, keep stored water at the right heat and see that the water is moving, and act fast if the system is acting up. I, Adelaide Crowe, would say: find out who is maintaining the hot water and where it is going and do not put off an investigation until the shower makes you cough.
Legionella Questions Answered
You will encounter these after a hot water system with no papers is inherited or a temperature reading is called into question. The answers are short and practical but context is everything.
Can Legionella be in tap water?
It is to be found in water naturally enough, but the danger of illness is whether it multiplies and is made airborne in fine droplets. Drinking is not how one is usually exposed. Give closer heed to the aerosols from a spa or shower.
Is 50°C sufficient?
No outlet temperature can vouch for the whole system. What will reduce scald risk at a fixture may not do so in storage. One has to look at the vessel, the delivery points and the circulation loop as a whole and be sure the building is in line with Australian requirements.
Put the heater up?
Not without cause. In some systems raising the storage temperature is fine, but absent or faulty mixing devices will raise the scald risk. Let a licensed plumber make the change and check the outlets.
Do you have to test in the home?
As a rule no. There is no need for routine testing unless health authorities have directed it or there is a complex shared system, a high-risk setting or a cluster of illness. Maintenance is a more sensible preventive measure.
Clean it yourself?
For the most part you can, keeping accessible shower fittings in order and making sensible use of an outlet. But leave the disinfection, chemical additions and any work on the pipework or valves to a professional, particularly where vulnerable people are concerned.
