In response to a Public Petition by the Scottish Burned Children’s Club and others to the Scottish Executive and subsequent Consultation process, the Scottish Building Standards Agency has announced that in all new and refurbished buildings, the maximum temperature of delivered hot water to a bath must not exceed 48°C. This temperature can be safely maintained by a thermostatic mixing valve (TMV) that blends hot water from the water heater at approximately 60°C with cold water, to produce hot water at a temperature that will not pose a serious scalding threat.

Although the Consultation Paper proposed for all bathroom fittings to come under the new legislation, the consensus reached by consultees was that it should only apply to the bath fitting as showers and basins do not pose such a significant scalding threat.

The Consultation Paper proposed a set temperature of 43°C, but this was subsequently determined as being too low and 48°C was suggested as a suitable maximum temperature. 48°C may also sound quite a low temperature, but it is in fact too hot for comfortable bathing but is considered to be sufficiently hot for an adult to top up a cooling bath. For young children and the elderly, whose skin is thinner, more sensitive and therefore more vulnerable to scalding, 48°C would be uncomfortably hot, but would still be significantly safer than water at 60°C. The adjacent table (Information from DTI Burns and Scalds in the home, 1999) shows relative exposure times at different temperatures that would cause a scald injury.

Another issue raised by the consultees was the flow rate. There is a perception that a TMV may restrict the flow such that the bath will take too long to fill and will cool too much in the process. This of course is entirely dependent on the size of the mixing valve. The Heatstat T2 TMV from Horne Engineering has been designed and developed to meet the requirements of the domestic market and in particular to address the flow rate issue.