How To Set Hot Water Heater Temperature 

Setting the correct hot water temperature of your home hot water heater is critical to having a safe and effective hot water supply.  Without the proper knowledge of how to set and check your hot water temperature, you could be putting you and your family at risk.

Can you set your hot water heater temperature?  The answer is yes!   But before we start adjusting dials on your hot water heater, let's take a look at how you can select the best hot water temperature for your home.

What is the right temperature to set the hot water heater?

Is there one temperature that's right for every home?  The answer is no.  The ideal hot water temperature for your home depends on a few factors which we'll get into in a little bit.  But a general range of temperature for your home's hot water heater should be between 120-140 °F. What's right for you?  Let's take a look at a few considerations.

Dangers of high water temperature 

Hot water heaters have a wide temperature adjustment range.  By turning up the dial too high, you can easily create a dangerous hot water temperature?  How dangerous?

Hot water temperature set too high can produce a serious burn in just a few seconds of exposure.

If you have young children or people with disabilities in your home, extra care must be taken to set a water temperature that will reduce the risk of scalding.  In addition, there may be local and state codes that dictate the maximum hot water temperature for these same reasons.  Be sure to check with these authorities for the rules that may apply to your home.

With respect to scalding prevention, a safe hot water temperature is 120 °F.

But before we adjust the hot water heater temperature down, let's consider the flip-side of have the temperature set too low.

Dangers of low water temperature

What is the danger of  a too low hot water temperature setting?  The short answer is...Bacteria!  According the Occupational Safety and Health and Administration (OSHA), hot water heaters that operate below 140 °F can provide optimal conditions for the growth of the Legionella bacteria.  Exposure to this microorganism can lead to Legionnaires disease - a serious disease which hospitalizes 8,000 to 18,000 people per year in the United States alone.

Tip: According to OSHA, water temperatures above 68 °F can provide the right conditions to promote the growth of Legionella bacteria.  So for homes in hot climates, water heated by the air in cold water lines can be unsafe as well.  In these cases, steps should be taken to keep the cold water lines below this critical temperature.

But wait, 140 degree hot water can scald your skin in less that five seconds.  So whats the right temperature setting for your hot water heater?

Best hot water temperature for you

In addition to the safety aspects of a too high or too low hot water temperature mentioned here, there are other considerations to select the best water temperature for you.

Running out of hot water.  If the water temperature is set on the low side, less cold water is mixed with the hot water from the hot water heater and the hot water supply is used up faster.  Having a higher hot water temperature will allow more cold water to be mixed with the hot water supply making for a more plentiful supply of water at the point of use such as the shower.  Note: this does not apply to "tankless" hot water heaters where a constant supply of the desired hot water temperature is available.

Energy savings.  Higher temperature setting on the hot water heater will increase energy you will use to keep the hot water tank idle with hot water.  

A hot water heater temperature setting between 120 and 140 degrees Fahrenheit is the range you should consider.

So taking everything into consideration, you will have to select a hot water temperature that makes sense for you and your family.

Measure hot water temperature before you make any changes 

Before you start making any hot water heater adjustments, start by determining your current hot water temperature.  Why do you have to measure the water temperature?  Most hot water heaters have indicator dials where the the temperature is set.  Why not just use these markings?  The simple answer is that these indicator dials on the hot water heater may not be accurate. You can use a meat thermometer to measure the hot water temperature.  

Start at sink is closest to the hot water heater.  This will give you faster results since you won't have to wait for the hot water to travel to a farther distance in your house.  Make sure the test location is not limited in temperature by a anti-scalding fixture (more on these types of fixtures later).  Place a glass on the bottom of the sink under the faucet.  You don't wan to hold the glass with hot water while you're taking the water's temperature.  Turn the water on the maximum hot setting and let the glass flow over into the sink.  Dip the thermometer probe into the water being careful not to get the rest of the thermometer wet.  Keep the probe in the water until the temperature reading stabilizes.  This could take a few minutes.  Write this number down.  This is your starting point temperature.

How to set the temperature on the hot water heater

You've measured your hot water temperature and found its not ideal and you want to make a change.  What's next?  You'll need to locate the temperature adjustment feature on your hot water heater.  Each hot water heater is different.  So consult the manufacture's manual to locate the temperature adjustment.

Typical gas hot water heaters have a temperature adjustment dial near the bottom of the tank and will look something like this:

If the hot water heater temperature dial indicates temperature settings, they can be used as a guide for making the adjustment.  But since the temperature dial may not be calibrated, you should rely on hot water temperature measurements.

At this point, adjust the temperature dial hotter or colder as you think might hit your ideal hot water heater temperature.  Small changes are best.  You're done, right?  No!  You need to remeasure the hot water temperature to make sure the setting is correct.

Here's an example.  The hot water heater before any changes measured a very scalding hot 148 °F.  The hot water temperature was measured at the faucet over time.