What are Sentinel Outlets and What Temperature Should They Be?

Anyone researching the subject of legionella control, general water safety and how to keep on top of it should know about sentinel outlets, what they are, how to locate them and what the hot and cold water temperatures should be.

Sentinel taps are an important aspect of water safety, so if you’re involved in monitoring or maintaining a water system, you should know what they are and why they have a crucial role to play in water temperature testing.

We’re going to cover sentinel water outlets or taps in this article, answering many queries that arise surrounding this topic.

What is a sentinel outlet?

A sentinel water outlet is one that has been selected to gauge the temperature of the water flowing through it. Not all water outlets or taps qualify as sentinel outlets – only those that are closest to and furthest away from the water storage tank are confirmed as being sentinel water outlets. Depending on the water system, the water storage tank could be replaced by a water boiler or a calorifier.

Testing the water temperature at these important taps helps to identify whether the system is adequately managed against the risk of legionella bacteria.

What should the water temperature be at a sentinel tap?

The required water temperatures at a sentinel outlet depend on whether it is a hot or cold water tap.

Cold water sentinel tap temperatures

In the case of cold water, the flow temperature should be below 20 degrees Celsius. This temperature must be achieved within one minute of turning on the tap.

Hot water sentinel tap temperatures

In the case of a hot water tap, the ideal temperature should be at least 50 degrees Celsius. The exception is within healthcare environments, where a minimum temperature of 55 degrees Celsius should be observed. These water temperatures should be achieved within two minutes of turning on the tap.

Do you need to use a special thermometer to measure water temperatures at sentinel outlets?

No, you don’t need to use a special thermometer but you should test it first to make sure it works correctly and that it can accurately measure the temperature of running water. You can also use it to measure the water temperature in other parts of the system, such as in a water storage tank. In this case, you should make sure you can see the reading and be sure it is accurate.

In some instances, people find a digital thermometer is easier to use for this purpose. It’s not necessary though – all you need is a thermometer you can trust to work and provide accurate readings.

Why are sentinel taps closest to and furthest from the water source the water comes from?

It might seem more logical to regularly test water temperatures at random outlets rather than staying with the same ones all the time. However, it is necessary to make sure the water temperature is within the right range once it leaves the boiler, calorifier or water tank. You also need to be sure that it is still within that temperature range once it reaches the furthest point from the source of water.

For example, let’s assume there is a hot water storage tank, and you test the water at the sentinel tap being fed from it. You find the water temperature measures 45 degrees Celsius instead of the required 50 degrees Celsius or above. This tells us that the water in the storage tank may not be at a safe temperature and may therefore be at increased risk of developing legionella bacteria.

In another example, you may have tested the temperature of the water in the tank and found it to be above 50 degrees Celsius and therefore compliant with safety regulations. Now, let’s assume you then test the temperature of the hot water coming from the furthest sentinel outlet being served by this tank. This temperature is found to be below the required 50 degrees Celsius. This tells you that it is dropping below a safe temperature at some stage between the tank and the sentinel outlet from that tank. You can then take action to make sure the hot water temperature is maintained throughout the system.

Is it necessary to test other water outlets throughout the system?

It is ideal to test all other outlets periodically as well, as it will help you gain a better picture of what’s happening throughout the water system. This applies to both hot and cold outlets. Keeping accurate records will give you an opportunity to look back on the results to make sure nothing is amiss.

Does the required water temperature change when the outlets include thermostatic mixing valves?

In some cases, particularly in healthcare settings, hot water taps may be required to have thermostatic mixing valves (TMVs) installed. These keep the hot water temperature at specific outlets at a safe level for those who may be at risk of scalding if the water temperature goes too high.

In this case, the hot water temperature won’t reach the usual levels required when testing these sentinel outlets (and indeed any others with TMVs). This means that the water should be tested before it enters the TMV, otherwise an inaccurate reading will be gained.

For instance, the hot water in the pipe might be of an acceptable temperature, whereas the water coming from the tap with the TMV installed should be at no more than 44 degrees Celsius to avoid scalding.

Be sure to test tap water temperatures throughout the entire water system to be alert to any potential issues

Testing water temperatures at sentinel outlets gives a good picture of whether the hot and cold water is at safe temperatures to avoid the growth and proliferation of legionella bacteria at certain points in the water system. Of course, the legionella risk assessment should identify any problem areas and recommend the removal or reduction of risks wherever possible.

A good example of this in relation to water temperature is a run of pipework that is no longer used. This doesn’t necessarily need to be capped off as it may lead to an infrequently used bathroom, for instance. However, there is a possibility that water could flow into that pipe and cool while there. It then becomes a risk through its lowered temperature and the fact that it might also become stagnant. In such circumstances, if the bathroom can’t be removed then regular flushing of any outlets used by it should be carried out.

By considering water temperatures throughout the system and testing temperatures via sentinel outlets, it is much easier to be sure the hot and cold water temperatures are at the correct levels to ward off the spread of legionella bacteria.

Expert legionella and water safety specialists

Water Treatment Services offer a range of specialist legionella and water safety solutions to support those responsible for the safety of water systems including business owners, landlords, the statutory duty holder and responsible person.

Contact us today to learn how our water safety specialists can help you manage your water systems, maintain regulatory compliance and so keep people safe.

With offices in London serving the South and South East England, Manchester (North West), Birmingham (Midlands), Bristol (South East England and Wales), Leeds (North and North East) and Glasgow (Scotland), supported by regional teams of specially trained technicians and engineers we can offer specialist Authorising Engineer support, legionella risk assessments, training, water quality analysis and other risk management solutions throughout the UK and Internationally.

Contact us today to learn how our water safety and legionella management solutions can help you.