Guidelines for the control of Legionnaires' disease EHS Environmental Health Standards

6.5 Thermostatic Mixing Valves

Tepid water can be provided by the use of Thermostatic Mixing Valves which mix hot and cold water to provide water at a predetermined temperature. These valves can overcome the necessity for the long-term storage of tepid water and should be located close to the point of use.

Mixing valves shall be of a fail-safe type, and regular maintenance is necessary to ensure correct performance. There is a risk of scalding to people in institutions by malfunction of these valves. In addition, the temperature of the water from taps or showers serviced by mixing valves should be checked by staff prior of use by patients to ensure that patients are not subjected to any risk of scalding.

6.5.1 High risk categories

For high-risk categories, the flowing procedure should apply. Flush outlets weekly at full flow for 15 seconds. Remove showerheads monthly and heat disinfect, preferably in a dishwashing machine where the temperature of the hot water is at a minimum of 70 degrees for five minutes.

6.5.2 Low risk categories

Outlets that are infrequently used should be flushed at full flow for 15 seconds on a weekly basis.

6.5.3 Maintenance procedures

Where mixing valves are installed, the following maintenance requirements are recommended:

a) Check the outlet water temperature with an accurate thermometer at least fortnightly to detect the start of any drift in outlet temperature from the required setting.

b) Every twelve (12) months carry out a comprehensive maintenance service in involving the complete dismantling the valves for inspection and cleaning. Replace any faulty parts and replace parts recommendedin the manufacture's service instructions. In areas with poor water quality, regular comprehensive servicing may be required.

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"Hot Water Burns Like Fire"

As stated by the Queensland Health Department. Thermostatic Mixing Valve's have many advantages and it is alarming that every year over 1100 people in Australia are burnt by hot water,when a simple device exists that can reduce these numbers dramatically -" Thermostatic Mixing Valves ".

Hot water is normally preset at temperatures of 65ºC and above. Water at this temperature can cause full skin thickness burns in less than two seconds for an adult and less for infants. Hazards of hot water can manifest when individuals living in a community environment, through some incapacity (age, mobility, and mental illness) can't avoid contact with hot water.

Employers and persons in control of workplaces are under an obligation stated in Sections 28 and 30 of the Workplace Health and Safety Act 1995 to ensure that health and safety of their workers and otherpersons within a workplace are adhered to. In order to achieve a safe outlet temperature, the most accepted method of temperature control is the use of thermostatic mixing valves.

These valves mix water to a perfect temperature and assure that persons can not be scalded. Incorporated as a safety feature of the TMV's is a fail-safe (hot water safety shut-off). This is activated if cold water supply ever fail during the mixing process.

The use of Thermostatic Mixing Valves can overcome many risks involved with scalding and are of great benefit to all organizations. A high performance product, that delivers warm water at a precise temperature to the user has a fail safe mechanism built in. They have a longer warranty are fully serviceable.

Manufacturers state valves must have yearly maintenance.

There are options to reduce the risk, e-mail us for information.
See Workplace Health and Safety Alert 96-I-47
Go to http://www.whs.qld.gov.au/