There has been an enormous amount of media attention focused on thermostatic mixing valves since the November 2003 launch of the TMV2 scheme and the announcement that the revision of Part G of the building regulations will include some sort of requirement with regards to the control of hot water temperatures. This initially generated a virtual feeding frenzy for a few months as the topic du jour in the trade magazines as well as some daily newspapers, radio shows and even breakfast TV. Opinion was and still is split: the pro-TMV supporters are ecstatic at the government decision as a long overdue safety measure, whilst the anti-TMV camp viewed the decision as more “nanny state” interference. Whatever the sceptics may protest, the facts are that hot water is the number one cause of severe scalding injuries among young children, and every year an average of 437 children under five are seriously scalded in the bath. Actual figures are probably higher as many less serious scalds go unreported. Our opinion and that of the Child Accident Prevention Trust (CAPT), and the Thermostatic Mixing Valve Manufacturers Association (TMVA) is that if the government has the opportunity to legislate a safety measure for the home, which is proven through years of use in the NHS and health service sector, is readily available and which would prevent even one child from scalding, let alone over 400 - then why not get on and do it?!
And to their credit, they are.
At the moment the proposed changes to all of Part G are in a consultation phase, so input is being taken from many different areas of industry and the private sector to understand how best to implement the TMV and other regulations, and what form they should take - the “nuts and bolts” of it. Everyone who has been involved in working towards this legislation agrees that the control of hot water temperatures is required. The questions needing answers now are to do with: “how?” How do you control it? What temperature do you deliver it at? Which outlets need protection?
While the idea of using TMVs in domestic properties in the UK is quite new (except in the case of thermostatic showers, which have been around for years) other parts of the world have used this system with great success for a very long time. To make sure that a workable and logical regulation is implemented, it is worthwhile to look at and learn from the experiences in these countries.
Australia first made the fitting of TMVs mandatory in 1994 (in South Australia), with the last state (New South Wales) implementing it in 1999. New Zealand actually lead the way, making it law in 1990. In both countries the legal requirement is backed up by the combined standard ANZ3500 as well as several performance related standards. In Canada, the fitting of TMVs has also been made a requirement by a change in the National Plumbing Code as of mid 2004 and is again backed up by the approvals that TMVs must meet to be considered compliant, namely CSA B125 or ASSE 1016.
In the UK a scheme has already been set up by BuildCert to test and approve valves for the domestic market; this is called the TMV2 scheme and it is based on the European standards BSEN1111 and BSEN1287. It has been set up to ensure that when the building regulations do come into force, a suitable mechanism for third party testing of the valves and their compliance to the standards is in place. So now we know the valves are necessary, a regulation is being prepared, a standard exists for compliance and an approval scheme is in place to ensure the valves are fit for purpose. The only question that remains is how should the system be configured and the valves installed to best satisfy all the demands of the end user for both safety and comfort.
In the following section we will look at the thinking of the pioneering regulators in Australia, New Zealand and Canada to see what can be learned from their experiences.
In both Australia and New Zealand the decision of the governing authorities was taken that to control the temperature of the hot water a thermostatic mixing valve should be installed at the point of the hot water generation i.e. on the hot water heater itself. The hot water thermostat should be set so that the water in the heater is at a minimum of 60°C in order to control the growth of legionella while the mixing valve should be set to supply hot water to the sanitary outlets (those used primarily for ablutionary purposes) at a temperature not exceeding 50°C. Neither how the water temperature is controlled nor where the valve is to be installed (at the heater or at the point of use) is specified: this is left to the installing plumber to decide upon, as long as the requirements of the installation standard are achieved. The governing authorities' decision was based on a number of factors:
Typical installation showing how a TMV could be used to control the temperature in a sanitary hot water distribution system for a domestic property.
Typical installation using a TMV to control the distribution temperatures for an entire bathroom.
1. The water heater is the single biggest risk area for the growth of bacteria because of the volume of water it contains, so it must be set at a high temperature to kill the bacteria.
2. Although water at 50°C can still cause a scald injury, the time that it takes for such an injury to occur changes from 2-3 seconds at 60°C to 5 minutes at 50°C so there can be considerably more time time to react to the situation where a thermostatic control is fitted than in an installation where delivery temperature is uncontrolled.
3. Fitting individual TMVs on each outlet was thought to be a far too costly and difficult operation. It was felt that the public would be more likely to accept the fitting of one valve rather than five or six in each house. Cost was and is a major factor to be considered: one tempering valve fitted to a water heater may cost as little as 40 pounds, whereas in a two or three bathroom house to fit valves at each point of use could run into many hundreds of pounds. It was further felt that a more palatable, less costly and invasive regulation would have a stronger take up and therefore would ultimately keep the public safer than if multiple valves - that never actually got installed - were specified.
In Canada the factors that were examined and the decisions that were made are almost identical to the Australian experience. In the end the decision on how to write the requirement came out very similarly indeed, although the people writing the standards in each country came to their conclusions independently. As of mid 2004, The National Research Council (NRC) Standing Committee on Building and Plumbing Services adopted a change to the Plumbing Code that requires water supplied by fittings in residential buildings to be limited to a maximum of 49°C (120°F).
In Canada this requirement can be met either by a master mixing valve at the heater or by mixing valves fitted at each outlet. Setting the temperature to 49°C (120°F) at the water heater is not deemed to be acceptable.
As you can see, the UK is not acting in a vacuum on this issue; in addition to the countries mentioned above several European countries, including France and Holland, are also considering the issue of hot water temperatures and how best to address it under forthcoming legislation.
It is imperative, as we make these decisions in the UK regarding how to write the new regulations, that we ensure all of the needs of the domestic market are catered for. Safety must be a priority but, unlike the commercial healthcare market, comfort and the option to have a hot bath must also be taken into account. A regulation that is not followed because it is too complex, unworkable or financially unsustainable is worse than no regulation at all.
The Heatguard® TMV2, approved under the BuildCert TMV2 Scheme and suitable for most domestic bathrooms.
The Heatguard® TMV2 2in1 from Reliance Water Controls®.
Written by Eric Winter, Technical Manager at Reliance Water Controls Ltd
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