Legionella & Water Monitoring

Most taps are used weekly if not daily, which helps to keep water moving to make it difficult for bacteria to settle and grow. However, in commercial settings, many outlets are seldom used if at all. Examples might include office showers, school changing room showers, accessible toilets, and bib taps. Stagnation is arguably the number 1 cause for legionella proliferation, and therefore plays a vital role in your legionella control and management.

All infrequently used outlets should be flushed every 7 days (or twice weekly in healthcare) to ensure water does not stagnate and encourage legionella growth. Outlets should be flushed until a stable and compliant temperature is reached.

Knowing what outlets are infrequently used – there are 2 good indicators to tell us what outlets need to be added to the weekly flushing regime. Number 1 – you know you do not use the outlet. If it’s rarely used or an unoccupied area, it should be put onto the weekly flushing regime. Number 2 – non-compliant temperatures. If your outlet is not reaching the desired temperature range within the allowed timeframe when most other outlets do, this indicates that the outlet may be infrequently used and should be placed onto the weekly flushing regime.

Temperature plays an important role in legionella bacteria control and management as the legionella bacteria can proliferate between 20-50°C and has even been known to grow at 54°C, with legionella’s most favoured temperature being 37°C (body temperature) which is why it can be dangerous to humans once contracted causing illness such as legionnaires disease, pneumonia, Pontiac fever, and the common cold and flu. In many ways monitoring data to ensure you fall into these water quality parameters is one of the best ways to ensure your water systems meet regulations.

Temperatures must be reached within a specific timeframe. This allows us to ensure temperature testing remains consistent and allows us to determine the frequency of use of the outlet and potential areas of stagnation or risk.

Temperatures are required to be taken from all heat sources and the sentinel points of a water system. Sentinel points are the monthly temperature points at the nearest and furthest outlets of each water system. For example, taking the sentinel points from a cold-water storage tank would consist of taking the temperature from the nearest tap to the tank and the furthest away. For heat sources, this means taking the temperatures nearest and furthest from all heat sources. This may be a cylinder, electric water heater, boiler or otherwise. However, in the case of an instant water heater with a single outlet such as a shower, the outlet becomes the nearest and furthest so one temperature would be all that can be taken.

Temperature timeframes

Hot temperature – 1 minute

Cold temperature – 2 minutes

Temperature guidelines

Hot outlet – 50°C (55°C in healthcare)

Cold outlet – <20°C

TMV* outlet – 38-43°C (ranges vary for showers/baths)

Scalding – 44°C

Heat sources

Cylinder and flow – 60-65°C

Cylinder return – 50°C (55°C in healthcare)

Combination water heater – 60-65°C

Boiler – 50-60°C (55°C minimum in healthcare)

Electric water heater – 50-60°C (55°C minimum in healthcare)

Instant water heater – 50-60°C (55°C minimum in healthcare)

*TMV – thermostatic mixing valve, blends hot and cold to create a reduced, non-scalding temperature. Often required for vulnerable persons and in healthcare.

Limescale is a great source of nutrients for legionella. Limescale can be found anywhere in water systems where there is hard water. The UK suffers from hard water due to the chalk limestone earth below the ground that finds its way into our reservoirs that supplies our mains water. Therefore, all outlets should be dismantled, cleaned, and descaled to remove the presence of limescale. This includes taps, spray heads, tank cleaning, showerheads and hoses.

Taking the temperature from the re-circulating return loop quarterly for subordinate temperatures.

POU legionella filters should be replaced quarterly to ensure they are in working order.

An expansion vessel is a small white, blue, grey, or red tank. The white, blue, and grey vessel colours are to identify water system expansion vessels and the red is to identify heating system expansion vessels. Each vessel includes a rubber diaphragm that goes across the middle, where the bottom half of the vessel is filled with water and the top half with pressurised air. When water is heated at the heat source (like a cylinder) it may expand as much as 4%. The expansion vessel allows this expanded water (increase in water size) from the heat source (cylinder) to flow into the expansion vessel where the bottom half of the vessel (water) may push the diaphragm up into the top hair (airside) to allow for the expansion in water.

So why do we need to flush an expansion vessel? Well, there are 2 primary reasons. One the expansion vessel is a dead end, and as such does not allow water out of it and therefore encourages stagnation both inside the vessel and all the pipework leading to it from the feeding tee (branch of pipe that leads to it). Secondly, the diaphragm is made of rubber, which is a great source of nutrients for legionella.

The guidelines outline that we must flush the expansion vessel for six months to remove stagnant water from the vessel and relevant pipework.

A filter’s job is to cleanse the water impurities and allow for good quality water to pass by and therefore provide us with good quality water free from bacteria and the like. And in doing so the filter will become dirty itself. You will often see an internal filter that initially looks like a clear white tube that eventually turns brown/black with impurities over time.

Most manufacturers have given this timeframe of 6 months before a water systems filter needs to be replaced or cleaned.

Ultraviolet lights should be serviced routinely to ensure they are kept in working order.

An annual review is an important part of checking your water quality parameters for legionella testing and control. At this stage, your risk assessments, logbook, schematic, and other records will be reviewed by an engineer to confirm the status of your legionella control and management. This will ensure that you have all the technical guidance required to meet regulations as well as monitor the level of dissolved oxygen in your system.

Coldwater storage tanks overall as a design will not change from year to year but the condition of the tank internally certainly can. Coldwater storage tanks are subject to poor temperatures (too hot or freeze), foreign bodies (bugs, animals), sediment (from mains), biofilm (from stagnation), wall spores (bacteria), and so on. Therefore, it is important to undergo both the internal and external water quality monitoring and tank conditions annually, as a minimum.

Hot water cylinders are subject to continual heat changes that may increase the risk of legionella through non-compliant temperatures. They also require temperature gauges, pipe insulation, and should be purged periodically to remove any internal limescale, debris, or sediment. Cylinders are prone to limescale build-up and an inspection and drain down (purge) of the cylinder will help to remove unwanted items within the cylinder and ensure high water quality.

A combination water heater consists of a cold-water storage tank on top feeding the hot water cylinder below, hence the name combination water heater. Therefore, both the tank and cylinder inspections and servicing must take place on a combination water heater.

TMV or thermostatic mixing valves are blending valves that mix the hot and cold water to reduce the risk of scalding where temperatures are often set to 41°C, 3°C lower than the scalding starting temperature for vulnerable persons at 44°C.

TMVs are fitted with filters that protect the valve, where these filters are prone to blocking with limescale, sediment, and other matter. Therefore, a TMV should be serviced at least annually as recommended by most manufacturers. TMV servicing, is one essential water quality monitoring step that should not be missed, it will often include temperature calibration, failsafe testing, and cleaning and disinfection of TMV parts amongst other actions where required.

Whilst you are required to undertake monthly temperature monitoring throughout the year at your sentinel points. You are also required to take the representative temperature at other points in the system to gather information on the rest of the water system. This could be made up of 10% of outlets in the system from areas you do not normally take the temperature from when undertaking monthly temperatures.

Manufacturers recommend that water softeners should be serviced annually to check levels of dissolved oxygen and provide technical guidance. This often includes a regeneration process where backflow is created to remove any bacteria or otherwise within the water softener system. Additionally, a review of the brine (salt) tank and other elements will be reviewed to ensure a safe and suitable working condition.

It is recommended that legionella sampling or a legionella risk assessment is undertaken periodically or at least annually, in order to ensure you receive all the technical guidance required to meet regulations. The number of water samples required will depend entirely on your water system. For example, samples should be taken from dead legs or areas of stagnation, cold water storage tanks, and all sentinel points to provide an accurate overview of your water quality parameters and the water system’s condition.

Water quality monitoring plays a crucial role in safeguarding our environment and ensuring the quality and safety of our water systems. There are many ways to conduct water quality monitoring, and one of the most essential aspects involves collecting and analyzing monitoring data, often through the collection of water samples. These water samples help experts assess various water quality parameters, including dissolved oxygen levels, a key indicator of aquatic health. By meticulously examining water quality parameters, we gain insights into the overall health of our water systems, ensuring they meet the highest standards for water quality and safety. There is a range of other risk systems that require more bespoke management. For more information please contact our team. Below we have a list of water systems that commonly require regular legionella risk assessments:

• Ultrasonic humidifiers/ foggers
• Spray humidifiers
• Air washers
• Emergency showers
• Sprinkler and hose systems
• Swimming pools/ whirlpools/ jacuzzis
• Horticultural misting systems
• Dental chair
• Vehicle wash systems
• Fountains and water features
• Industrial processing water systems
• Reverse osmosis
• Water dispensers
• Evaporative cooling systems
• More

Water monitoring is essential for the safety not only of our drinking water, but also our environment. Water monitoring technologies have been devised to help scientists and engineers gather accurate information in real time so they can monitor temperature, flow, sediments, dissolved solids, pollution, identify problems, changes in trends, and be alerted to any emergencies. 

Methods of water quality monitoring 

There are different ways of monitoring water in order to collect water quality data, such as:

Sampling – Taking water samples from the environment or from water systems enables specialists to test the chemical condition of water at that given point. The water is then tested for different parameters such as dissolved oxygen, biological and chemical contaminants. In the past, the water samples had to be taken by hand which meant someone had to physically visit the site – a time consuming and sometimes difficult process when samples need to be taken from less accessible areas. The sample would then have been sent off for analysis in order to determine the water quality. More recently, sensor technology has been developed to aid remote, real-time water quality monitoring, saving resources and response time. 

Remote cameras – Installing remote cameras allows you to visually monitor the water in real time. Changes in colour, blockages, damage and water levels are easy to assess at any given time without the need to travel to the location.  

Smart sensors – The development of the Internet of Things (IoT) has enabled low-cost remote monitoring solutions that are being developed all the time. This has encouraged the mass development of systems, using improvements in battery development, solar power and telecommunications to improve monitoring for businesses and environmental groups alike. 

Remote water temperature monitoring 

When it comes to legionella risk management, remote water temperature monitoring is vital. Part of your business’s health and safety requirements when it comes to managing the risks of legionella bacteria is dependent on the temperature of your water. With the use of remote temperature readers installed throughout your water system and constantly monitoring your water, you can reduce the likelihood of accidentally creating the conditions in which legionella bacteria breed. 

Legionella bacteria thrive in water temperatures that are between 20-45°C. It is therefore necessary to ensure that, in order to protect the people who use the building, your water is kept at temperatures that are hostile to the bacteria to stop them becoming established. Your cold water system must therefore be kept below 20°C, the temperature it stops multiplying and goes into a dormant state. Your hot water system must be stored at a temperature in excess of 50°C which is the minimum temperature needed to start killing the bacteria. It’s important to bear in mind that the hotter the water temperature, the more effective it is – after two hours at 50°C, 90% of the bacteria will have been killed off. If you heat your water to 60°C, you’ll kill 90% of the bacteria in just two minutes. If your water is 70°C or higher, all the legionella bacteria present will die instantly. 

Legionella Thermometer Remote Water Monitoring

Our remote water temperature monitoring service is designed to help you keep your water systems safe. We will install sensors in your hot and cold water systems that will collect data and send it to your server. This means users can monitor your water in real time without the need to do physical temperature checks, saving your company a lot of time, especially if you have multiple sites. Contact us to find out more.