Warning! Anti-scald shower valves can scald you!
By Ron George,CPD,
President, Ron George Design & Consulting Svcs.
Editor’s Note: The following is a continuation of last month’s column from Ron George.
Every year, thousands of people suffer serious thermal shock and/or scalding injuries in showers or combination tub/shower fixtures. Tens of millions of currently installed code compliant shower valves, referred to as anti-scald or safety shower valves, can potentially scald people.
Plumbing inspector’s responsibility
I recently spoke to a group of about 80 at a code inspectors’ conference. I asked by a show of hands how many inspectors carried a temperature gauge or thermometer with them on a final inspection to check for the maximum temperature at a shower or tub/shower. Only a couple raised their hands. When I asked why, one person said that his municipality would not pay for expensive testing equipment. I explained that you can a food thermometer (available at the grocery store for about ten bucks) can be used. Another said he never thought to use a thermometer and that he tested the water temperature by feeling it; as long as it did not get too hot, he considered it all right. Most attendees said they had not given the problem much thought. Several said they were going to purchase thermometers.
Model Plumbing Code requirements for showers
The two model plumbing codes in the United States have the following language covering showers:
The 2009 International Plumbing Code
424.3 Individual shower valves. Individual shower and tub-shower combination valves shall be balanced-pressure, thermostatic or combination balanced-pressure/thermostatic valves that conform to the requirements of ASSE 1016 or ASME A112.18.1/CSA B125.1 and shall be installed at the point of use. Shower and tub-shower combination valves required by this section shall be equipped with a means to limit the maximum setting of the valve to 120°F (49°C), which shall be field adjusted in accordance with the manufacturer's instructions. In-line thermostatic valves shall not be utilized for compliance with this section.
The 2009 Uniform Plumbing Code
418.0 Shower and Tub-Shower Combination
Control Valves. Showers and tub-shower combinations in buildings shall be provided with individual control valves of the pressure balance, thermostatic, or combination pressure balance/thermostatic mixing valve type that provide scald and thermal shock protection. These valves shall conform to ASSE 1016 or ASME A112.18.1/CSA B125.1. Gang showers, when supplied with a single temperature-controlled water supply pipe, shall be controlled by a mixing valve that conforms to ASSE 1069. Handle position stops shall be provided on such valves and shall be adjusted per the manufacturer’s instructions to deliver a maximum mixed water setting of 120°F (49°C). The water heater thermostat shall not be considered a suitable control for meeting this provision
Limit stop readjustment needed. The maximum temperature limit stop on all pressure-balancing type shower valves should be readjusted seasonally to correct for changes in the incoming cold water temperatures. These temperatures can vary as much as 50 degrees in some areas, which can correspond to a relative change in the outlet temperature, based on the delivered hot water temperature and the ratio of hot to cold. I recommend having maintenance workers check the limit stops at least twice a year to assure the maximum hot water temperature does not exceed 120 F.
All compensating type shower valves should be readjusted every time there is a change in the domestic hot water system that could affect the system temperature. The limit stop should be readjusted when a water heater is replaced, when the master thermostatic mixing valve temperature is readjusted, when the circulating pump is replaced, when the thermostat on the water heater is adjusted or if any work is done on the hot water system that can potentially change the hot water delivery temperature. Manufacturers of all hot water system components should mention this in their literature.
Schools and institutional facilities
For gang showers in schools or prisons, where the bather cannot adjust the temperature, there is typically an on-off shower valve or a metering button. Shower valves for this application are set by staff, and the thermostatic mixing valve should comply with the standard titled ASSE 1069-2005 - Performance Requirements for Automatic Temperature Control Mixing Valves for gang showers. In all cases water should be flowed from the shower valve long enough to assure that the water temperature is not a hazard.
Ron George is president of Plumb-Tech Design and Consulting Services LLC. He has served as chairman of the International Residential Plumbing & Mechanical Code Committee. Visit www.Plumb-TechLLC.com, e-mail Ron@Plumb-TechLLC.com or phone 734/755-1908.