A little more than nine years ago, the ASSE International Board of Directors formed the Scald Awareness Task Group with this purpose in mind: To work with our industry partners and various advocacy groups to promote public awareness of the potential hazards and injuries caused by scalding water.
During those nine-plus years, five different task groups were formed to write five different white papers on the topic of potential scald hazards associated with residential hot water systems. The first four are available on ASSE International’s website at www.asse-plumbing.org/resources:
- Scald Hazards Associated with Low-Flow Showerheads
- Understanding Potential Water Heater Scald Hazards
- Adjustment of Automatic Compensating Valves to Prevent Potential Scald Hazards
- Guidelines for Temperature Control Devices in Domestic Hot Water Systems
The latest project for the Scald Awareness Task Group was the development of the fifth white paper, Recommended Installation Practices for Residential Storage Type Water Heaters to Reduce the Danger of Scalds, which is also available for download at www.asse-plumbing.org/resources.
As each white paper is completed, the task group – sometimes as many as 36 individuals – is thanked for their time and expertise, and then the group is disbanded. Then, when a new topic is approved, a call for participants is made to the industry and each interested individual must complete an Application for Working Group Membership. This way, each paper has new task members with particular interests in that topic. In fact, we are currently accepting applications for our next white paper, which will cover recommended installation practices for tankless/on-demand water heaters. Details about applying can be found after this article.
That’s enough about how the Scald Awareness Task Groups work. Now let’s talk about the new white paper, with a very long title:
Recommended Installation Practices for Residential Storage Type Water Heaters to Reduce the Danger of Scalds
The first draft of this paper was developed in Aug. 2017 and the final draft was completed in Oct. 2018. A total of 22 industry professionals contributed both their time and expertise to the development of the paper. The group included manufacturers, professional engineers, industry association members, master plumbers, general interest individuals, code officials, inspectors, a building commissioner, and labor representatives.
Although this paper is not a “how-to” guide or manual, it focuses on the recommendations that an installer should follow when installing or replacing a residential tank type water heater in order to reduce the dangers of scalds. One of the most dangerous misconceptions in our industry is that the water heater alone is capable of delivering a consistent water temperature at the point of use. This paper explores why that misconception can create a false sense of security and, most importantly, how the dangers of scalding from excessive water temperature can be reduced.
Another focus is on what must be done with the hot water distribution system when replacing a residential storage type water heater. Too often the installer only replaces the water heater without checking or possibly knowing the effect that the new water heater has on the system. Back in the old days, we called this a “slip out – slip in” installation and many plumbers would brag on how fast they could replace a water heater.
The paper discusses the four most common causes of hot water scalds from an improperly installed storage type water heater:
- The perception that water heaters alone sufficiently control water temperature at the point of use. The water heater thermostat on standard residential tank type water heaters is NOT capable of controlling the temperature of the hot water distribution system.
- Failure to address the impact of a new or replacement water heater on the hot water distribution system temperature.
- Improperly installed water heaters.
- The Stacking Effect.
Let’s take a look at each of these causes and their solutions:
1)
Many plumbing installers and consumers believe that water heaters alone can sufficiently control the water temperature at the point of use. This misconception can create a false sense of security for the homeowner, especially when many groups advocate turning the water heater thermostat to a lower temperature to avoid scalds. This thought may help, but it will not prevent scalds at the point of use.
Water heater thermostats cannot be considered precision controls, as they can experience wide variations in storage temperatures. These variations in water temperatures can be attributed to causes other than the accuracy of the thermostats. For many types of storage water heaters, the location of the thermostat near the bottom of the tank reacts to the incoming cold water temperature to activate the means to heat the water. The hotter water accumulates at the top of the storage tank.
The only true solution to control the water temperature to the system is to install a temperature actuated mixing valve listed to ASSE 1017 at, or near, the water heater.
2)
When a water heater is installed, its impact on the distribution system and points of use is often not considered. The installer must be aware of the effect that the new water heater has on the temperature of the hot water system. For example, in a replacement scenario, the new water heater may have a different rating or may be set to a higher temperature. Both of these changes will impact the water temperature at the point of use, which can result in a scald injury.
Another good example: a water heater that has been in use for a long time and has not been maintained properly by draining at least twice a year may have a good bit of sediment buildup at the bottom of the tank. As this sediment built up over the years, the homeowner would turn up the thermostat to keep the hot water at a desired temperature. Then, when the water heater fails and is replaced, the installer sets the thermostat on the new water heater at the same position on the dial as the old heater. This could be a very hot setting with a clean tank (no sediment buildup) and the hot water at the point of use could be significantly higher than with the previous water heater.
The solution is that the installer must run the water heater through one complete cycle to check the outlet temperature of the water heater and check all of the downstream temperature limiting devices (at the source, shower or tub/shower combination compensating type valves, whirlpool or soaking tub compensating type valves, etc.) for proper water delivery temperatures. The temperature limit stops must be reset when necessary. If there are no temperature limiting devices in the hot water distribution system, the installer must inform the homeowner of the potential scald hazards that are present.
Being a former contractor, I realize that many contractors reading this are thinking, “You want me to stay another hour to check temperature? Time is money.” Lawsuits are also very expensive – think about it.
3)
When water heaters are not installed in accordance with local codes and manufacturers’ installation instructions, the potential for scalds is greatly increased. The model plumbing codes do not tell you how to install a water heater, but they do tell you what safety devices must be installed and what safety precautions must be followed. All major manufacturers include very explicit installation instructions with their water heaters. Both the codes and the manufacturers’ installation instructions must be followed.
The best solution is to know the code in your area and to read and follow manufacturers’ installation instructions.
When a water heater is not properly installed, including verifying the required temperature settings of the downstream temperature control devices, the potential for scald injuries is dramatically increased.
To help reduce the danger of scald burns from extremely hot water at the point of use, it is recommended, in all scenarios, to install a temperature actuated mixing valve for hot water distribution systems compliant to ASSE 1017 at the hot water source – the water heater. This will allow the water heater thermostat to be set at a higher temperature, which accomplishes two additional benefits:
- Increases the available amount of hot water, and
- Controls the growth of legionella bacteria in the water heater.
The ASSE 1017 device at the outlet of the water heater can then be set to the industry recommended maximum temperature of 120°F to control the hot water system temperature. The accuracy of an ASSE 1017 listed device, for a typical residence flowing a total of less than 5 gpm, will control the outlet water temperature within ±3°F, based upon the performance requirements in the standard.
Installing an ASSE 1017 compliant temperature actuated mixing valve at the water heater does not replace or negate the requirement of point of use temperature limiting devices at showers, tub/shower combinations, whirlpool bathtubs, soaking tubs, etc.
4)
The “Stacking Effect” is caused by short, repeated water heating cycles from small hot water uses, which transfers more heat to the already heated water. The hotter water rises to the top of the water heater. This can increase the water heater outlet temperature by 20 or more degrees above the set point of the water heater thermostat at the outlet. This increase in water temperature may increase the risk of scalds.
The most effective solution for controlling the potential increase in water temperature in the hot water distribution system due to the Stacking Effect is to install a temperature actuated mixing valve listed to ASSE 1017 at, or near, the water heater.
The Manufacturers’ Recommendations section of the new white paper includes quite a bit of information from various installation instructions. The opening paragraph of this section states:
A water heater can deliver scalding temperature water at any faucet in the system. Be careful whenever using hot water to avoid scalding injuries. Certain appliances, such as dishwashers and automatic clothes washers, may require increased water temperature. By setting the thermostat on a water heater to obtain the increased temperature water required by these appliances, the potential for scald injury increases. To protect against injury, you should install an ASSE approved mixing valve in the water system. This valve will reduce point of discharge temperature by mixing cold and hot water in branch supply lines. Such valves are available from the manufacturer of your water heater or a local plumbing supplier. Please consult with a plumbing professional.
The section on plumbing codes mentions:
Most model plumbing codes identify the maximum safe temperature to prevent scalding as 120°F. The plumbing codes also state that the water heater thermostat shall not be used as a control for scald prevention.
All codes are constantly changing and updating, and it is the installer’s responsibility to check with the local authority having jurisdiction (AHJ) for any local requirements or amendments to the code in their jurisdiction before installation.
The section covering the installer responsibilities reiterates much of what was said earlier in the paper. Some of the responsibilities that the installer must be aware are:
- Water heaters are to be installed per the manufacturer’s installation instructions or the local codes, whichever is more stringent.
- In all installations, the installer must check the water temperature at the outlet of the water heater, at the closest fixture, and at all shower, tub, or tub/shower combination units. Set the limit stops on any temperature limiting devices to 110°F or at a temperature not to exceed that in the local codes.
- If temperature-limiting devices are not installed in the hot water distribution system, the installer should make the owner aware of the potential scald hazards that are present.
- TO LOWER THE POTENTIAL OF SCALD INJURIES, IT IS STRONGLY RECOMMENDED TO INSTALL A TEMPERATURE ACTUATED MIXING VALVE FOR HOT WATER DISTRIBUTION SYSTEMS LISTED TO ASSE 1017 NEAR, OR AT, THE SOURCE. Once properly set, this valve will reduce the temperature in the water distribution system to a safer temperature.
In my many years of experience as a plumber and as a plumbing contractor, I have seen many advances made by water heater manufacturers and model / local codes to make the delivery of hot water safer for the homeowner. Some advances include resettable temperature and pressure relief valves, expansion tanks on closed systems, electronic ignition, flame arrestors to prevent the ignition of combustibles near the water heater, and more. Is it time for the model codes and/or manufacturers to require a temperature-limiting device at the source of the hot water – the water heater? I think so!
Water heaters, as we know them today, have been around for close to 100 years. Today, with all of the controls and safety devices mentioned above, water heaters are safer than ever before. They have helped increase the quality of our lives by making the delivery of hot water much simpler than in the “good old days.” The writing of this paper and all of the previous papers in no way makes any attempt to say that the water heaters in today’s market are unsafe. The concern or purpose of writing these papers is only about the delivery temperature at the point of use to reduce the dangers of scalds.
Take the advice of the Scald Awareness Task Group’s new white paper, along with the advice found in many manufacturers’ installation instructions, and install a temperature activated mixing valve for hot water distribution systems compliant with ASSE 1017 at, or near, the hot water source and set the outlet temperature to 120°F when installing or replacing a storage type water heater.
The entire Recommended Installation Practices for Residential Storage Type Water Heaters to Reduce the Danger of Scalds white paper is now available for download at www.asse-plumbing.org/resources.
ASSE International Calls for Scald Awareness Task Group Members
The ASSE International Scald Awareness Task Group is now accepting applications as it reforms to develop a new white paper concerning recommended installation practices for residential tankless/on-demand water heaters to reduce the danger of scalds.
This new white paper will be a companion piece to the group’s latest white paper, “Recommended Installation Practices for Residential Storage Type Water Heaters to Reduce the Danger of Scalds.” The task group has also published four previous publications: “Guidelines for Temperature Control Devices in Domestic Hot Water Systems,” “Adjustment of Automatic Compensating Valves to Prevent Potential Scald Hazards,” “Understanding Potential Water Heater Scald Hazards,” and “Scald Hazards Associated with Low-Flow Showerheads.”
“During the development of the ‘Recommended Installation Practices for Residential Tankless/On-Demand Water Heaters to Reduce the Danger of Scalds,’ the group discussed whether to include tankless/on-demand type water heaters in the paper,” said Richard J. Prospal, IPP, FASSE, Chairperson of the ASSE International Scald Awareness Task Group. “It was finally decided to have two distinct papers for the two distinct types of water heaters, especially with the development and completion of three new ASSE product performance standards for tankless type water heaters – ASSE 1082 (Water Heaters with Integral Temperature Control Devices for Hot Water Distribution Systems), ASSE 1084 (Water Heaters with Temperature Limiting Capacity), and ASSE 1085 (Performance Requirements for Water Heaters for Emergency Equipment).”
All task group meetings for this paper will be conducted via conference call — no face-to-face meetings are anticipated. The first conference call will be held in mid-July.
Participation in the Scald Awareness Task Group is open to all interested parties; membership in ASSE International is not required. All who are interested in volunteering must complete a working group application — even if they have participated in the development of past ASSE scald awareness white papers. Working group applications can be downloaded online at http://bit.ly/asse-wg. Applications must be completed and emailed to Prospal at rjprospal@yahoo.com no later than June 16.
