What temperature must hot water be in a commercial kitchen?

Maricopa County's Hot Water Supply Requirements guide says the water heater must furnish "a continuous supply of hot water, at a thermostat set-point of at least 120ºF, to all hand sinks, dish/utensil sinks, mechanical warewashing machines, rinse sinks, service sinks, garbage can washers, shower heads" and similar fixtures. The same sentence says that water must arrive "within 45-seconds at all times." Our page on the 45 second and 60 foot rule covers that timing.

The guide defines hot water as "potable water at a temperature equal to or greater than 110ºF." So the heater is set at 120 degrees F or higher, and the water at the fixture has to be at least 110 degrees F.

Legionella is a reason some facilities go higher. The guide says "maintaining water heater systems at 140°F or higher and providing water to faucets at a minimum of 122°F will reduce the growth and likelihood of Legionella." That is advice, not the plan review minimum. Our page on Legionella water management plans goes further. A hotter tank also raises the scald risk at the tap, which is why mixing valves matter.

Hand sinks are the one place where the county wants water that is warm, not hot. The guide gives two statements that fit together:

• "Hot water for hand washing shall be at least 110ºF supplied through a mixing valve or combination faucet in food-related establishments."
• "Tempered water in food-related establishments shall be maintained at a temperature of 100°F to 110°F."

The plan review checklist repeats the second: "Hot water or tempered water (100ºF to 110ºF) is required at all sinks," and "All sinks, including mop/service sinks, must have mixing faucets or valves." In practice, a food-business hand sink runs on a mixing valve or a combination faucet set to land in the 100 to 110 degrees F range at the spout. The guide adds that temperatures "are measured from the faucet." Emergency eyewash stations follow a different rule, with tepid water through an ASSE 1071 valve; see what plumbing an emergency eyewash station needs.

Why that range? The guide cites ASTM testing of hand washing products and says "a water temperature of 100°F to 108°F is the most effective temperature range for proper hand washing." Water that is too cold does not lather. Water that is too hot makes people rush or skip washing.

### The federal floor

The FDA Food Code is the model rule that state and county food codes start from. Section 5-202.12 says a handwashing sink "shall be equipped to provide water at a temperature of at least 29.4oC (85oF) through a mixing valve or combination faucet." It also says "a steam mixing valve may not be used at a HANDWASHING SINK." So the federal floor is 85 degrees F, and the county sets a tighter range for food businesses. The steam mixing valve ban is worth knowing when a kitchen is being fitted with a boiler or steam source.

The Food Code also says a self-closing, slow-closing or metering faucet must give at least 15 seconds of flow "without the need to reactivate the faucet." That is a faucet detail, not a temperature, but it is checked at the same inspection.

### Non-food hand sinks

The county treats non-food buildings differently. Its guide says "in non-food establishments, hot water or tempered water (85°F to 110°F) under pressure is required at all hand-wash sinks, service sinks, garbage can washers, and showerheads." So a lobby restroom in an office is on the 85 to 110 degrees F range, while a restaurant hand sink is on the 100 to 110 degrees F range.

Manual dish washing in a three-compartment sink has two temperature points.

1. 1Wash sink. The county guide says the wash solution must be kept "at a minimum of 110°F with liquid detergent." The FDA Food Code agrees. Section 4-501.19 says the wash solution "shall be maintained at not less than 43oC (110oF) or the temperature specified on the cleaning agent manufacturer's label instructions." The Code's own explanation is that below 110 degrees F, "animal fats that may be present on the dirty dishes would not be dissolved."
2. 2Sanitizing step. If a manual sink uses hot water to sanitize, the county guide says the sanitizing compartment must have "an integral heating device that can maintain water at a temperature of at least 171°F." The Food Code says the same in section 4-501.111: "the temperature of the water shall be maintained at 77oC (171oF) or above," and section 4-204.116 also asks for the sink to have a heating device "capable of maintaining water at a temperature not less than 77oC (171oF)." A tank heater set at 120 degrees F cannot reach 171 on its own, so that compartment needs its own heater. Chemical sanitizing is the other option, and its temperature limits come from the sanitizer's label.

That is why the three-compartment sink is a plumbing question and a chemistry question at once.

A machine uses one of two methods, and the number depends on which.

• Low-temperature (chemical) machines. The guide lists a wash temperature of at least 120 degrees F. The Food Code says the same for spray-type machines that use chemicals: "may not be less than 49oC (120oF)."
• High-temperature machines. The Food Code sets the wash temperature by machine type: 165 degrees F for a stationary rack, single temperature machine, 150 degrees F for a stationary rack, dual temperature machine, 160 degrees F for a single tank, conveyor, dual temperature machine, and 150 degrees F for a multitank, conveyor, multitemperature machine. The final rinse at the manifold must reach 165 degrees F for a stationary rack, single temperature machine or 180 degrees F for other machines, and "may not be more than 90oC (194oF)."

A heater set at 120 or 140 degrees F cannot make a 180 degree F rinse. That gap is why high-temperature machines use a booster heater. Our page on whether a restaurant needs a booster heater for the 180 degree F final rinse explains it.

### Putting the numbers together

Here is the full list, with the source for each figure.

Use a thermometer at the fixture, not at the heater. The county measures at the faucet, and a long pipe run can cool the water before it arrives. These steps find most problems.

1. 1Run the hand sink for a full minute and read the temperature at the spout. If it is over 110 degrees F, the mixing valve needs adjusting. If it is under the range, the supply may be starved or the valve worn.
2. 2Check the wash sink with a probe thermometer after it is filled, not while it runs.
3. 3Look for a temperature gauge on the warewashing machine. The Food Code says a machine must have a temperature measuring device "in each wash and rinse tank" and "as the water enters the hot water SANITIZING final rinse manifold."
4. 4Test the last fixture on the longest run. If it takes longer than 45 seconds to get warm, ask about a recirculation loop. Our page on whether a recirculation pump is worth it covers how they work.
5. 5Ask your inspector or plan reviewer which figure applies. The county, the city and the sanitizer label can each add a rule, and the stricter one wins.

If the hot water runs out at the wrong moment, read why a commercial water heater cannot keep up. HQ Plumbing & Air is licensed and insured, and we can check the temperatures at your fixtures and tell you what needs to change. We offer free estimates and upfront pricing.