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Water systems can be a breeding ground for bacteria if not looked after correctly and it is crucial to ensure all water systems are monitored and inspected to prevent any legionella bacteria growth.
Legionella bacteria can cause a severe lung infection known as Legionnaires’ disease.
Last month we started our new Legionella series, in which we are giving you all the information you need to be confident that you’re doing all that you can to keep your water and your property safe for the people that use it.
We started with weekly flushing and this month’s instalment focuses on the thermostatic mixing valve, better known in the water world as TMV.
What is a TMV?
TMV is a thermostatic mixing valve, a device that sits under a wash hand basin or a sink in many highly used properties, including schools, care homes and hospitals.
The T-shaped valve has a hot pipe on one side and a cold pipe on the other, and is used to combine the two before it reaches the point of use, where it is blended to a manageable, warm temperature. The TMV reduces the risk of scalding, particularly in settings where people are vulnerable.
It is important to be aware of the growth band temperature for Legionella growth in a TMV, as while it is more of a scalding risk than a Legionella risk, there is still a risk.
TMVs should be within a two-metre radius and not supplying multiple outlets to ensure that the length of blended pipework within the legionella growth band is not increased and the TMVs should be supplying exclusive outlets to minimise this.
Why does a TMV need to be serviced?
If a TMV is not serviced, over a long period of time the moveable parts can stop working due to wear and tear or hard water erosion, meaning the temperature can go too high and increase the scalding risk.
Legionella bacteria thrive between 20-45°C and so if the temperature is too low, this can also cause a risk. It is vital to ensure that the water stays within safe parameters by keeping up to date with TMV checks.
It is a legal requirement to have a TMV serviced annually, in which the TMV is taken apart, cleaned and disinfected. The parts are all checked one by one and the TMV is inspected for potential leaks, corrosion or excessive scale.
The TMV should also have a fail safe test every six months to ensure there is no cold water supply failure. In this test, the cold tap is switched off so it doesn’t enter the valve, which should shut down the TMV.
What is a TMVT?
The TMVT is a thermostatic mixing valve tap, which is most commonly used in hospitals. It offers the same service as a TMV but it is built into the tap itself, rather than being a separate valve under the sink.
If there’s no pipework between the valve and the tap, then there’s a very low risk of a drop temp in the growth band.
Anyone involved in water system management who requires more information on water safety and legionella should sign up for the Acorn Safety Services legionella awareness course.
Alternatively talk to our team of experts by calling 01604 930380.
