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Thermostatic mixing valves are valves that blend hot and cold water. They use a temperature sensitive element which expands and contracts depending on the temperature of the water entering the valve.
This changes the size of the openings through which the hot and cold water enters the valve, balancing the temperature of the water leaving the outlet e.g. the tap, and so reduces the risk of scalding accidents. Reliance is a world expert in this field.
Thermostatic mixing valves should be fitted in all public places and wherever there is the possibility that the outlet could be used by people who are judged to be at risk.
©Reliance Water Controls Ltd
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The HOT WATER BURNS LIKE FIRE slogan and picture define Reliance’s campaign to raise the awareness of scalding injuries, specifically in the home. The striking image of a child about to climb into a steaming hot bath to get his toy is an all too realistic representation of real life situations that can occur in the home. Our bathroom scene has been used extensively by the Childrens Burn Trust (CBT), Child Accident Prevention Trust (CAPT), Thermostatic Mixing Valve Manufacturers Association (TMVA) and of course by Reliance Water Controls in the UK to highlight the need for temperature control of hot water systems in homes, offices, hospitals, care homes, schools and other public buildings.
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General Information
Reliance Water Controls began operations in the UK market in 1986 and shortly after this the first thermostatic mixing valve appeared on our shelves for sale. Since then Reliance has gone on to be a founder member of the TMVA and to be instrumental in the writing, promotion and support of the NHS model engineering specification D08 - now a worldwide recognised benchmark standard for thermostatic mixing valves. Pioneer and market leader in the sale of thermostatic mixing valves, Reliance has also worked with Buildcert, providing industry input into the creation of the TMV2 and TMV3 schemes.
Reliance actively supports the education of the public about the dangers of scalding. Through working with organisations such as the CBT , CAPT, and RoSPA, Reliance has helped to get scalding on the agenda for review in the building regulations for domestic housing in England and Wales. The company provided advice, support and technical expertise to the SBSA (Scottish Building Services Agency) when it was decided in 2006 to introduce legislation requiring the fitting of thermostatic mixing valves as standard in domestic properties in Scotland.
TMV3 Scheme
  The TMV3 Scheme is the third party valve accreditation programme which is administered by Buildcert (a division of WRc). It has been set up to test independently whether valves submitted are suitable for use in high risk commercial healthcare applications within the UK. The performance testing required in order to comply is based on the NHS model engineering specification DO8 for thermostatic mixing valves. Other important factors are also considered: for instance, an applying company must also prove that they comply with ISO 9001 or a suitable equivalent quality control system, the valves are checked for correct marking so they can be identified in the field, packaging and instructions are checked to make sure they conform to guidelines issued by Buildcert.
If Buildcert is satisfied that all the requirements of the scheme have been met, it will issue a certificate granting a five year period of approval for the TMV. The valve will also be entered onto the list of approved products which is kept on the Buildcert website and is updated regularly. After five years, the manufacturer must resubmit the valve for another full TMV3 test procedure: if successful, a new certificate will be issued and the entire cycle starts over again
This level of third party compliance testing is unheard of in the rest of the world and helps to keep the UK at the forefront of hot water safety and thermostatic mixing valve technology and product development.
TMV2 Scheme
  In November 2003, Buildcert launched a new system for the testing of thermostatic mixing valves called the TMV2 scheme. This is very similar to the TMV3 version but with one big difference: where the TMV3 scheme is intended to be used to certify valves for use in the high risk healthcare sector, TMV2 valves are specifically designed, built and tested for the domestic market.
From April 2010, England and Wales join Scotland in requiring, as part of the building regulations, the control of hot water temperature to a safe maximum at the bath outlet in domestic bathrooms, which can be achieved by the fitting of a thermostatic mixing valve.
In Scotland, regulations came into force in 2006, requiring control of outlet hot water temperature for baths and bidets: this applies to all new build domestic properties where the building warrant was applied for after 1st May 2006 and is also a requirement in properties undergoing bathroom renovation works which involve the movement or replacement of the bath or bidet.
In England and Wales, the revisions to Part G of the Building Regulations (Hot water supply and systems), which are effective from 1st April 2010 include the requirement that baths in new homes are fitted with a protective device (ie a thermostatic mixing valve) to limit the temperature of hot water.
TMV Selector Chart
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Environment
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Appliance
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Is a TMV:
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Valve type?
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Required by legislation or authoritative guidance?
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Recommended by legislation or authoritative guidance?
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Suggested best practice?
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Private dwelling (England, Wales, N Ireland)
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Bath
Basin
Shower
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Yes
Yes
Yes
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TMV2
TMV2
TMV2
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| Private dwelling (Scotland) |
Bath
Basin
Shower |
Yes |
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Yes
Yes |
TMV2
TMV2
TMV2 |
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Housing Association dwelling
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Bath
Basin
Shower
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Yes
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Yes
Yes
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TMV2
TMV2
TMV2
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Housing Association dwelling for the elderly
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Bath
Basin
Shower
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Yes
Yes
Yes
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TMV2
TMV2
TMV2
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Hotel
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Bath
Basin
Shower
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Yes
Yes
Yes
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TMV2
TMV2
TMV2
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NHS nursing home
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Bath
Basin
Shower
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Yes
Yes
Yes
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TMV3
TMV3
TMV3
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Private nursing home
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Bath
Basin
Shower
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Yes
Yes
Yes
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TMV3
TMV3
TMV3
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Young persons’ care home
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Bath
Basin
Shower
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Yes
Yes
Yes
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TMV3
TMV3
TMV3
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Schools, including nursery
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Bath
Basin
Shower
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Yes, but 43°C max
Yes
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Yes
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TMV2
TMV2
TMV2
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Schools for the severely disabled, including nursery
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Bath
Basin
Shower
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Yes, but 43°C max
Yes
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Yes
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TMV3
TMV3
TMV3
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NHS hospital
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Bath
Basin
Shower
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Yes
Yes
Yes
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TMV3
TMV3
TMV3
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Private hospital
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Bath
Basin
Shower
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Yes
Yes
Yes
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TMV3
TMV3
TMV3
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Group Mixing
Group mixing is a form of centralised mixing at one point to serve a number of outlets. Many of the principles are the same as for single outlets and in some cases the same valves are used. The length of the pipe run between the hot water storage vessel or the secondary circulating system and the group thermostatic mixing valve should be such that the shower head or outlet furthest from the valve is supplied with hot water within 30 seconds; and the maximum pipe run after the mixing valve should be such that the required mixed water temperature should be reached at the furthest outlet within 30 seconds. These requirements are primarily to prevent growth of legionella bacteria, but also for the practical reason that users dislike having to wait for the water supply to warm up. A typical push button shower control will keep the water running for about 25 seconds and if the user has to press the button more than twice to obtain suitably hot water, this could give rise to complaints. The two main applications for group thermostatic mixing valves are group showers and ranges of wash basins. The discharge temperature for group showers should be 38°C to 41°C depending on the surrounding ambient temperature. Similar temperatures should be used for basins.
Tempering Valves
Tempering valves are the predecessors to the thermostatic mixing valves we see marketed today under the TMV2 and TMV3 banners, but there is one big difference. Both TMV2 and TMV3 type valves are designed to be fitted at or as near as practically possible to the point of use (ie the tap), to give extremely sensitive and fast response times to changing system conditions. A tempering valve is not designed for applications where very precise temperature control and rapid failsafe shutdown are required; instead, it is designed to control the water temperature in the whole system, be it heating or sanitary hot water. Because of this it is designed and manufactured to meet a different set of criteria from the point-of-use thermostatic mixing valve.
The Reliance range offers tempering valves for many different applications; these include controlling hot water temperatures in distribution systems that use solar heat as a source of energy, or controlling and stabilising temperatures in underfloor heating systems.
Typical Installations:
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Heatguard BF2-2 TMV in a domestic environment. |
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Promix 22-2 in a healthcare environment. |
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All images ©Reliance Water Controls |
Sink on LEFT: Typical Healthcare Basin Installation with Heatguard DC3 and Senselec Infra-red Swan Neck Tap to prevent cross contamination.
Sink on RIGHT: Heatguard LS2 TMV2 installed in commercial non-critical environment such as senior school or leisure centre for controlling basin temperature. |
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