The recent outbreaks of hot water Legionella in Queensland mainly in hospitals is of concern. These, for the most part, were warm water systems which are not the same as your home hot water storage tank.
With hot or warm water systems there is always some risk but every system checked in recent weeks by Whywait Plumbing has had hot water temperatures that virtually eliminate all risk. However, there is almost no risk of you or your family contracting Legionella bacteria as a result of it breeding in your home hot water system.
Legionella Transmission Via Hot Water
Legionella transmission is airborne via respiratory droplets containing the bacteria. Warm water and domestic hot water systems that are contaminated will generally see the transmission of the bacteria in a shower that has not been used for a period of time.
Hot Water Preventative Measures For Legionella
Hot water systems should be maintained so that water at the point of use at any tap or outlet is 50°C or more after having been turned on for one minute.
Hot water systems should not be used until they have reached 50°C especially if they have been turned on for any period.
Generally, domestic hot water systems should have a temperature of 60°C or higher in water leaving the hot water storage tank.
DO NOT turn down the thermostat on an electric hot water storage tank to below 60C.
Hot Water Temperature For Preventative Of Legionella
Hot water systems should be maintained so that water at the point of use at any tap has a temperature that affects the survival of Legionella as follows:
- Above 70 °C – Legionella dies almost instantly
- At 60 °C – 90% die in 2 minutes
- At 50 °C – 90% die in 80-124 minutes, depending on strain
- 48 to 50 °C – Can survive but do not multiply
- 32 to 42 °C – Ideal growth range
- 25 to 45 °C – Growth range
- Below 20 °C – Can survive but are dormant, even below freezing
What Is Legionella Bacteria or Legionnaires Disease
What it is:
- Caused by the Legionella bacteria, commonly found in creeks, ponds and soil.
- Rare in people under 20 years, with those over 50 years old who smoke or have a weak immune system particularly susceptible.
- Non-specific flu-like symptoms including fever, headache and muscle aches, developing within a week of breathing in the bacteria.
- Usually progresses rapidly with pneumonia symptoms, high fever, shortness of breath and chest pain typical.
- A person with the disease usually needs to be admitted to hospital for antibiotic treatment and care.
- Early diagnosis and antibiotic treatment important, and those treated usually begin to improve with three to five days.
Testing Your Storage Tank
For most homes, there is a very little risk of you having hot water legionella occur in your hot water storage tank unless you do really stupid things such as turn off your heating source.
An easy test of the storage temperature is to get a thermometer and test the temperature of your water from the overflow relief valve drain.
If you have any doubts about the temperature in your storage tank contact Whywait Plumbing to organise a service call to check your hot water system.
Judging by the number of phone calls in the last few days to Whywait Plumbing there is genuine concern amongst our clients over the threats posed to them from Legionella risk in their domestic hot water systems.
We can assure you whilst there is always some Legionella risk, there is almost no risk of you or your family contracting Legionella bacteria as a result of it breeding in your home hot water system.
The outbreak of Legionella bacteria in the hot water system at Wesley Hospital that killed a 60-year-old cancer patient and left a 46-year-old woman seriously ill has minor ramifications to be sure because all hot water systems can pose a risk.
That potential risk is why Whywait Plumbing is constantly advocating appropriate maintenance on your home hot water system to minimise that risk even further.
However, there is a huge difference between your home or domestic hot water system and the warm water recirculating system at Wesley Hospital. The Legionella outbreak in their warm water system has not been as a result of contamination in the hot water storage system or the hot water pipes but appears to be literally at the point of delivery from the shower where the water is cooler.
A warm water system is vastly different to your home hot water system with Wesley’s water temperature set between 42.5°C and 43°C. This is lower than the maximum 45°C legislated in the Plumbing and Drainage Act for hospitals. This low-temperature setting is a result of guidelines from Queensland Health that dictate hot water temperatures in hospitals be reduced to avoid the possibility of serious burns to young children and elderly patients. The downside of this requirement is that the possibility of Legionella bacteria surviving in reticulation pipes is increased. Water temperatures of around 46°C will kill legionella bacteria.
Warm water systems are typically found in care facilities, such as nursing homes, hospitals and child care centres, where water for purposes such as bathing and cleaning is provided at approximately 45°C to prevent scalding.
Your home hot water system if it is a storage tank is heating the hot water to between 60°C and 70°C. If you have a tempering valve or thermostatic mixing valve (TMV) installed then that has been set to deliver hot water at 50°C at each individual tap.
If you have no tempering valve installed, you virtually have eliminated all risk. But you have increased the risk of someone suffering a scalding from hot water. As always it is about managing risk.
However, there is an urban myth prevalent that you can reduce electricity costs by turning the thermostat down on an electric storage unit to 50°C. This is not recommended for many reasons but it will not save you electricity and to physically get a thermostat down that low requires physically breaking the locking mechanism on it that allows the setting to be between 60°C – 70°C. If you want to lower the delivery temperature the only acceptable and compliant method is to install a tempering valve.
In 99.99% of cases, the temperature ranges your hot water system operates in is almost certainly killing any Legionella bacteria. The risk if any, is after the storage tank in the reticulation pipes. By turning your shower on and running the tap with hot water first then cooling down with cold water to your desired shower temperature you are virtually eliminating what risk there is.
What the outbreak at Wesley Hospital has confirmed is that there is a risk from warm water and that maintenance of your hot water systems will manage and eliminate that risk.
What Whywait Plumbing do recommend is that you take advantage of our ongoing reminders and offers to service your tempering valves. This not only ensures that water is being delivered at 50°C but eliminates any possibility of Legionella. It also ensures you are complying with the requirements of most insurance policies in ensuring that routine maintenance is undertaken plus we provide you with a written report and a form 4 compliance certificate that is further evidence of your hot water unit being compliant.