Arizona's assisted living rule, A.A.C. R9-10-819(A)(6), requires hot water temperatures between 95 and 120 degrees F in areas used by residents. That is a floor and a ceiling. Separate wording requires enough hot and cold water for resident hygiene and sanitation. The state writes it as a manager's duty, not as a water heater setting.
What does the Arizona rule say about hot water?
The rule is A.A.C. R9-10-819(A)(6), part of the Arizona Department of Health Services (ADHS) licensing rules for assisted living facilities. It says the manager shall ensure that "Hot water temperatures are maintained between 95º F and 120º F in areas of an assisted living facility used by residents."
Three things stand out.
- It names a range, not a heater setting. The rule is about the temperature residents can get in the areas they use. Where the heater is set, and what valves sit between the heater and the tap, is the facility's design problem.
- The duty is the manager's. The rule begins "A manager shall ensure that," so the licensed facility carries it, whoever owns the building or services the equipment.
- It sits next to a supply rule. The same section requires that "The supply of hot and cold water is sufficient to meet the personal hygiene needs of residents and the cleaning and sanitation requirements in this Article." Water that is the right temperature but runs out at 7 a.m. still has a problem.
The same section also says premises and equipment must be "Free from a condition or situation that may cause a resident or other individual to suffer physical injury," and that equipment is "Maintained in working order." A tempering valve that has failed can create exactly that kind of condition.
ADHS treats this as a real inspection item. On its top-ten list of assisted living home deficiencies for November 1, 2019 through October 31, 2020, the hot water provision, R9-10-819(A)(6), appears at number 9 with a frequency of 55 citations. That list is a snapshot of one year, not a current ranking, but it shows inspectors do check the temperature.
Why is there a minimum as well as a maximum?
The rule does not explain its own numbers, but the reasons are easy to see. The maximum guards against scalds. Older adults are one of the two groups hardest hit by them. The U.S. Consumer Product Safety Commission says "The majority of injuries and deaths involving tap water scalds are to the elderly and children under the age of five," and that "Even if the temperature is 120 degrees, a five minute exposure could result in third-degree burns." The CPSC urges lowering water heaters to 120 degrees. The 120 degree ceiling in the Arizona rule lines up with that.
The floor matters for a different reason. Water that is merely warm is where Legionella can grow. CDC's guidance for potable water systems says "Legionella may grow at temperatures as low as 68°F (20°C)," and its water management checklist asks specifically about buildings that primarily house people older than 65, such as retirement homes and assisted-living facilities. So a facility cannot solve scalding by just turning everything down. The temperature has to stay hot enough, and the water has to keep moving.
How does a facility keep water at 95 to 120 and still control Legionella?
By separating storage temperature from delivery temperature. CDC's module says to "Store hot water at temperatures above 140°F (60°C)" and to "Ensure hot water in circulation does not fall below 120°F (49°C)." It then says to "Install thermostatic mixing valves as close as possible to fixtures." Put those next to the Arizona rule and the shape of a compliant system appears: hot storage, a circulating loop, and a tempering valve near the point of use that brings what reaches residents down into the 95 to 120 range.
The Arizona rule does not say how to do that, and it does not require a mixing valve by name. CDC's numbers are guidance for water management programs, not an ADHS rule. The facility's plumber and whoever writes its water management plan have to make the numbers work together, and the plan should be checked against the licensing rule, not the other way around. Our page on whether a Phoenix building needs a Legionella water management plan covers that side, and dead legs explains why unused branches defeat the loop.
What does the plumbing code add at showers and tubs?
Showers and tubs get their own temperature limiting rules in the plumbing code. The 2024 International Plumbing Code, Section 412.3, says shower valves "shall be equipped with a means to limit the maximum setting of the valve to 120°F (49°C)." Section 412.5 says bathtub valves "shall have or be supplied by a water-temperature-limiting device" meeting ASSE 1070, again limited to 120°F.
Phoenix adopted the 2024 IPC with amendments under Ordinance G-7397, and its published amendment list touches other sections (403.2, 410.2, 424.2 and 604.4 among them) but not these. Other Valley cities adopt their own editions, so check the edition and amendments in the city where the building sits. The details of how those valves work for residents who cannot react quickly are in our page on how senior living facilities prevent scalding at showers and tubs.
How can a manager check compliance?
Measure where residents use the water, not at the heater. A few practical points follow from the rule's wording.
- Test at the tap or shower outlet in resident areas, after running the water long enough to reach steady temperature, and keep a dated record.
- Check the farthest and the nearest fixtures. A system can be right at the front of the building and low at the end of a long run.
- Look for rooms where the temperature differs from the rest, since a worn mixing valve or a crossed fixture cartridge often shows up in one room first.
- Treat a complaint of "too hot" or "too cold" as a reading to take, not an opinion to settle.
- If the numbers are off, ask a licensed plumber to find the cause before turning the whole heater up or down, because the fix may be one valve.
Your licensing rule is what the inspector reads. The numbers in your building's water management plan, the IPC and the manufacturer's instructions all have to fit inside it. For related reading on supply problems, see why commercial water heaters run short of hot water.