How to Check and Adjust Your Tank Water Heater Temperature (2026) — Step-by-Step Guide

Please note: This guide is general reference for conventional gas and electric tank water heaters in single-family homes. Your heater’s own manual and rating label come first, and local rules may apply. It is not medical advice.

Introduction

Questions about water heater temperature usually start with one number, the setting on the heater. But three different temperatures are involved, and they are not always the same. The thermostat setting is what the control is set to. The stored-water temperature is the temperature of the water inside the tank. The measured tap temperature is what actually comes out of a particular faucet. This guide shows how to measure the tap temperature, how to compare it with the setting, and how to decide who should change a setting if a change is needed.

It covers conventional gas and electric tank water heaters in single-family homes. It does not cover tankless or heat-pump water heaters, boiler-fed or shared building hot water systems, or disinfection procedures, and it does not recommend one setting for every household. A federal safety agency and a public health agency give guidance for different risks, and the manual for your own heater comes before anything written here. For related topics, see our guides to a water heater with no hot water, flushing a water heater and testing the pressure relief valve. For tankless sizing, see our water heater sizing guide.

Three Temperatures: Setting, Stored Water and Tap

Manufacturers describe several reasons these can differ. A. O. Smith’s manual for an electric heater says repeated small draws can leave hot and cold water in the tank in layers, so the water can be as much as thirty degrees hotter than the thermostat setting, and that a hot surrounding area, a pre-heated water supply or a malfunction can also raise the temperature. Rheem’s manual for a gas heater says maximum water temperatures occur just after the burner has shut off. Heaters, controls and use patterns differ, so treat the setting as a starting point and the tap measurement as the check.

What CPSC and CDC Say, and Who They Are Written For

CPSC: preventing tap water scalds

The Consumer Product Safety Commission’s Publication 5098, “Avoiding Tap Water Scalds” (edition marked March 2012) is written for consumers and aims at preventing scald injuries. It says most tap water scald injuries and deaths involve the elderly and children under five, and that burns can happen quickly at higher temperatures and, with long enough exposure, even at 120°F. CPSC urges users to lower their water heaters to 120°F. It also says a thermostat setting of 120°F may be necessary to reduce or eliminate the risk of most tap water scald injuries, and suggests lowering the thermostat to the lowest setting that still meets the hot water needs of clothes and dish washing machines. The publication is short and dates from 2012, and its notes on adjusting heaters are general, so your manual governs how your own heater is adjusted.

CDC: germs in home plumbing

The Centers for Disease Control and Prevention’s page “Preventing Waterborne Germs at Home” (dated March 15, 2024) is written for households and addresses a different concern: germs that can grow in plumbing. About water heaters, CDC says keeping a home water heater between 130°F and 140°F can kill germs like Legionella in water but also increases the risk of burns. If you set a water heater above 120°F, CDC says to use valves that mix cold and hot water at the tap (thermostatic valves) to avoid burns, and it calls this especially important if young children, older adults or other people at increased risk of burns live in the home.

CDC also says to ask your healthcare provider about your risk of getting sick from Legionella and to discuss whether setting your water heater to 130°F or above is right for you. According to CDC, most healthy people do not get sick from these germs, and its page lists people who are more likely to, such as adults 50 and older and people with chronic lung disease or a weakened immune system. Read the full list on CDC’s page.

How the two fit together

These recommendations address different risks that can apply to the same household. CPSC addresses scald prevention for consumers in general. CDC addresses germ growth, explains that a higher setting raises burn risk, and ties higher settings to mixing valves and a conversation with a healthcare provider. Neither is a rule that fits every household, and this guide does not choose a setting for you. The right decision can reasonably differ depending on who lives in your home, any advice you have received from a healthcare provider, your appliances and your heater’s manual.

Before You Start

This guide assumes a conventional gas or electric storage tank heater in a single-family home. If you have a tankless or heat-pump heater, or hot water from a shared or boiler-fed building system, your situation is different and this guide does not apply.

Manuals differ more than you might expect

Manufacturers do not agree on how their heaters are adjusted, or on who should do it. Bradford White’s gas-fired manual shows several gas controls with different dial markings, notes that the direction that raises the setting is not the same on all of them, and says the dial ships at its lowest setting. Rheem’s manual for an electric model with an electronic control says not to try to set the temperature by removing the electronic control or the lower access panel. A Bradford White electric manual describes thermostat adjustment as work done inside the heater, which this guide does not cover. A. O. Smith’s manual for an electronic-control electric heater says water temperature should be adjusted primarily from the heater’s electronic control. Instructions written for one model, including any in this guide, may not apply to yours.

Step-by-Step: Check, Then Decide

Step 1: Find Your Manual and Rating Label

Find the owner’s manual that came with the heater. If you don’t have it, the heater’s rating or data plate lists the manufacturer, model and serial number you will need to find the manual on the manufacturer’s website or to ask the manufacturer for it. Read the sections on water temperature, scalding and adjusting the temperature. Note whether your manual identifies any control for owner use, and what it says about waiting after a change.

Step 2: Decide When to Measure

Manuals and public guidance give different timing advice, so use your manual’s if it gives any. CPSC’s publication suggests, for gas heaters, measuring first thing in the morning or at least two hours after hot water use. Rheem’s manual for a gas heater with an electronic display says reliable readings should be taken shortly after the burner cycles off, during a period of little or no use. Whatever timing you use, write it down with the reading in Step 4 so later readings can be compared.

Step 3: Measure the Tap Temperature

Use a thermometer made for measuring water temperature, and follow its instructions for how to use it, how long to wait for a stable reading and what temperature range it is rated for. CPSC’s publication and Rheem’s manual both describe measuring with a thermometer in the hot water from a faucet. Use the thermometer, not your hands, to find out how hot the water is. Measure at the faucet your household uses most for bathing or showering; A. O. Smith’s manual suggests checking several points of use, such as a bathtub faucet, a shower and a bathroom sink.

Step 4: Record and Compare

Write down the date and time, which faucet you measured, how long it had been since hot water was last used, the thermostat setting as it appears on the control (the exact mark, label or displayed value), and the thermometer reading. A tap reading that differs from the setting is not necessarily a problem, for the reasons in the section on the three temperatures.

A reading that is much higher than the setting, or that keeps rising, is different. A. O. Smith’s manual lists a thermostat problem or other malfunction among the causes of higher-than-expected water temperature. If that is what you see, don’t adjust anything. Contact the manufacturer or a qualified professional.

Step 5: Decide Whether a Change Is Needed

There is no number in this guide to match. Consider:

• Who lives in your home. CPSC’s concern centers on the elderly and children under five. CDC points to people at increased risk of burns and, separately, people at higher risk of illness from Legionella.
• Health advice. CDC says to ask your healthcare provider about your risk from Legionella and whether a setting of 130°F or above is right for you.
• Your appliances. CPSC suggests the lowest setting that meets the needs of clothes and dish washing machines. Some manufacturers’ manuals note that certain appliances may call for hotter water, so check the manuals for yours.
• Protection at the tap. CDC says to use thermostatic mixing valves if a heater is set above 120°F. See the section on mixing valves.
• Your manual. It may state limits, factory settings or warnings that apply to your model.

If the measured temperature fits your household’s needs and your manual’s guidance, you may not need to change anything.

Step 6: Decide Who Makes the Change

Only change a control that your exact manual explicitly identifies for owner use.

What counts as a qualified professional can depend on your manual and on local rules. Some manuals specify a qualified installer, service agency or service technician, and others refer to a licensed plumber or electrician. If you are unsure, ask the manufacturer or your local authority. This guide does not provide steps for opening panels, wiring or gas controls.

Step 7: Recheck After Any Change

Follow your manual’s instructions about how long to wait for the water to reach a new setting. Then repeat the measurement under the same conditions as before and record the result. Make one change at a time. If the readings are not what you expected, stop and contact the manufacturer or a qualified professional rather than making repeated adjustments.

Mixing Valves: What They Do and Why They Need a Professional Eye

A thermostatic mixing valve blends hot and cold water to limit the temperature delivered to the fixture it serves. It does not change the stored-water temperature in the tank. CDC says to use these valves at the tap if you set a water heater above 120°F. Manufacturers recommend them too, and they name different standards: A. O. Smith’s manual refers to point-of-use thermostatic mixing valves and to ASSE 1070, and Rheem’s manual recommends a valve that complies with ASSE 1017. Watts, a valve maker, says valves controlling bathing and washing fixtures are listed to ASSE 1016 Type T or ASSE 1070, while valves controlling water at the source of supply are listed to ASSE 1017.

Which valve is right depends on where it goes and what it protects. Its selection, installation and setting should follow the valve maker’s instructions and your heater’s manual, and usually call for a qualified professional. Valves also need upkeep: Watts says regular inspection is recommended and that how often a valve needs cleaning depends on local water conditions. The cost in this guide’s At a Glance box does not include mixing valves, their installation or their upkeep.

When to Stop and Call a Qualified Professional

• Your exact manual doesn’t identify a control for owner use, or says a qualified installer, service agency or service technician handles it
• The adjustment would involve opening panels, disconnecting power or handling gas or electrical parts
• The tap reading is much higher than the setting, or keeps rising
• Someone in your household may need a higher tank setting: ask your healthcare provider, and ask a qualified professional about mixing valves before anything is raised
• You smell gas, see damaged wiring or find water near electrical parts: follow your manual’s emergency instructions
• The heater leaks or its relief valve discharges: see our guides to a water heater leaking and to the pressure relief valve
• You live in a building where hot water is shared or supplied by a boiler: ask your building manager or landlord

Frequently Asked Questions

Q: What temperature should I set my water heater to?

There is no single answer in the published guidance. CPSC urges users to lower water heaters to 120°F to help prevent scalds. CDC says 130°F to 140°F can kill germs like Legionella but raises the risk of burns, says to use thermostatic mixing valves if a heater is set above 120°F, and advises asking your healthcare provider whether a setting of 130°F or above is right for you. Your household, your appliances and your manual all matter, so measure first and see Steps 5 and 6.

Q: Why is my tap temperature different from the thermostat setting?

The setting is not the same as the temperature of the water in the tank, and neither is the same as what comes out of a faucet. A. O. Smith’s manual says layering of hot and cold water in the tank can make the water as much as thirty degrees hotter than the setting, and Rheem’s manual says the highest temperatures occur just after the burner shuts off.

Q: Can I raise the temperature to prevent Legionella?

CDC says a setting between 130°F and 140°F can kill germs like Legionella but also increases the risk of burns. It pairs a setting above 120°F with thermostatic mixing valves at the tap and recommends asking your healthcare provider whether a higher setting is right for you. Raising the tank without those protections does not address the concern safely, and this guide is not medical advice.

Q: Can I adjust the thermostat myself?

Only a control that your exact manual explicitly identifies for owner use. Manuals differ: some describe an outside dial or display for owners, while others leave service to a qualified technician or say not to remove panels. If your manual doesn’t clearly identify an owner control, contact the manufacturer or a qualified professional.

Q: Does lowering the setting save energy?

CPSC and some manufacturers say lower settings conserve energy. The sources we read give no figures, so this guide doesn’t either. How much you would save depends on your heater and your use.

Q: Do my dishwasher and washing machine need hotter water?

Some manufacturers’ manuals note that certain appliances may call for hotter water, and CPSC suggests using the lowest setting that meets those appliances’ needs. Check the manuals for your appliances rather than assuming.

Q: What if I rent or my building has shared hot water?

This guide doesn’t cover shared or boiler-fed systems. CDC suggests checking with your building owner or manager about the steps they take. Ask your landlord or building manager before changing anything.

Q: What about tankless and heat-pump water heaters?

They are outside this guide because their controls and manuals work differently. Follow the manual for your model. For tankless sizing and selection topics, see our water heater sizing guide.

Sources and Further Reading

Primary sources used for this guide. Manufacturers revise their manuals, so check the current version for your own model.

• U.S. Consumer Product Safety Commission, Publication 5098, “Avoiding Tap Water Scalds” (edition marked March 2012)
• Centers for Disease Control and Prevention, “Preventing Waterborne Germs at Home” (March 15, 2024)
• A. O. Smith, Residential Electric Water Heater Installation Instructions and Use & Care Guide (electronic-control model)
• Bradford White, Gas-Fired Water Heater Installation and Operation Manual (238-51007-00)
• Bradford White, Electric Water Heater Installation and Operation Manual (238-44422-00)
• Rheem, Electric Residential Water Heaters manual with electronic control (AP21980)
• Rheem, Residential Super High Efficiency Water Heater Use & Care Manual (AP21831)
• Watts, “Thermostatic Mixing Valves” reference page

These are representative examples, not a complete survey of manufacturers. Documents were checked in October 2026.

Conclusion

The setting on a water heater, the temperature of the water in its tank and the temperature at your tap are three different things, and only the last is easy to check. Measure it with a water-temperature thermometer used as its instructions say, record it, and compare it with your setting and your manual. CPSC’s and CDC’s guidance address different risks and neither is a one-size setting, so decide with your household in mind and, where health is a factor, with your healthcare provider. Change only a control your exact manual identifies for owner use, and leave everything else, including mixing valves, to a qualified professional. For other heater problems, see our guides to signs your water heater is failing and no hot water, or the annual home plumbing inspection checklist.