Safe Water Heater Temperature – What Temperature Should You Set ?

Wow! Its' minus 20 degrees outside. Nothing gives you pleasure more than to take a warm shower or bath in this winter. Taking a hot shower is equal relaxing and soothing for body and mind in summer too. Besides relaxation, a hot shower has lots of health benefits. Our skin becomes dull and darker after a hard working day because of clogging pores due to dust, pollution, and toxins. A hot shower after that hard day will help to clean your skin acne as well as remove annoying back and whiteheads.

Are you suffering muscle pain? The most natural solution to relieve muscular pain is to take a hot water shower. It helps to increase muscle temperature thus relax the pain in minutes. You might be surprised to hear that hot water shower before a stress full exercise will help to release a copious amount of heat stress protein (HSP), which helps to boost up the performance. 

To get all this benefit, we have to have a good water heater. There are several categories of water heaters available in the market, mostly tankless or instantaneous and traditional storage type water heater is widely used. Typically, a question arises in our mind, how much hot is suitable for our skin? To get this answer, here we try to discuss the temperature settings of the commonly used storage type water heater.

About the question of temperature setting, two things come to our mind first –

One    - if we set too high temperature, there have a chance to be scalded by hot water.

Two  - if we set too low temperature, there is a risk to grow pathogens like Legionnaires’ disease  

What is it means by too high or too low temperature, to understand we may visit World Health Organization website. As per WHO

Temperature vs. chances of growing pathogens (Legionella Bacteria) 

Above 70°C (158°F)                     - dies all bacteria instantly

At 60°C (140°F)                           - 90% die within 2 minutes

At 50°C (122°F)                            - depending on strain 90% died in 80 -124 minutes,

At 48°C - 50°C (118°F - 122°F)    - can survive but lost the ability of multiplication

At 32°C - 42°C (90°F - 108°F)    - ideal temperature range for growth

We found a chart on temperature vs. time of scalding at professionals and home renovating experts of remove and replace the website.

Temperature vs. Time to proceed scalding/burn

At 120 °F                      - more than 5 minutes

At 125 °F                    - 1½ to 2 minutes

At 130 °F                   - about 30 seconds

At 135 °F                    - about 10 seconds

At 140 °F                   - about 5 seconds

At 145 °F                      - less than 5 seconds

At 150 °F                     - about 1 – ½ seconds

At 155 °F                      - in a seconds

Cautions: In case of severe burns immediately put the burned area in clean water

The US Department of Energy and the Consumer Product Safety Commission (CPSC) recommended temperature for commonly used water heaters 120°F, and according to another government agency the Occupational Safety and Health Administration (OSHA) declare 140°F as a safer temperature for public health. Now let’s arguing on this dilemma below –

The arguments for 120°F temperature setting:

If we set the water heater temperature at 120°F, we may get the following advantages as advice by the American Society of Sanitary Engineering –

Helps to cut down bills

Savings come from turning down of the temperature of your water heater subjected to standby loses and consumption. For each 10 degrees reduction, we can save 3-5% from our utility bills. If we set 120°F instead of 140°F we may save about $36 - $61 a year from standby heat losses and more than $400 from demand lose (according to the department of energy).

Environmental Friendly

By saving energy bills, we can protect our environment as well. If we set temperature of water heater at 120°F, it will burn less gas or fuel or consume less electricity. This way it leads to emit fewer greenhouse gases, which helps us to save our environment.

Resist deposition of mineral

Hard water buildup mineral deposition like lime, inside the hot water tank and plumbing pipes. If your household water is hard, by lowering the temperature of your water heater you may delaying the deposition of mineral.

Prevent to be scalding

If you have a child and elderly member in your home, they are more vulnerable to scalding by hot water of 140°F; it takes only 5 seconds. But if you set the temperature at 120°F scalding delayed up to 5 minutes. 

The arguments for 140° F temperature setting:

Well, we see lots of benefits to set the temperature at 120°F, so why we go for higher temperature.

In a study by Janet E. Stout, Ph.D., Director of the Pittsburgh-based Special Pathogens Laboratory warns that Legionella bacteria can flourish in stagnant water in tanks that semi-simmering at 100° to 110°.

According to WHO the chances of growing Legionella Bacteria is low if set the temperature at 120°F. But it still risks for those who are suffering autoimmune diseases like pneumonia. So, it recommended that if anyone has an autoimmune disease in your family set the temperature at 140°F to annihilating the bugs of Legionella Bacteria.  

For dishwasher the recommended temperature is 50 – 60 °C (122 – 140 °F) to get the optimum result. The new modern dishwasher has a built-in internal heating system but it absent in old type. So you have to set 140°F if you still using old type dishwasher.

Copper pipelines heated faster than PEX and remain for an hour; thus the risk of growing Legionella Bacteria in PEX is more than that copper pipes.

In the big houses, some branches of pipelines remain unused or rarely used which deposit stagnant water. The stagnant water of dead legs is an excellent breeding ground for Legionella Bacteria, as the temperature not raise as like main.

How you check your current temperature Settings?

Absent of temperature gauge in most of the water heater available in the market. We can get the idea about current temperature by seeing the thermostat temperature setting at water heater body. But most of the cases it is not clear enough.

Also, we can measure the temperature by a cooking thermometer. Set a particular point of the thermostat, turn it on, wait for sometimes, then take flow from faucet nearest to the water heater and measured by a thermometer.    

Which temperature setting is most suitable for you?

We have found two completely different but equally important view from above discussion. One says to save your child or elder person from scalded and to save energy cost it is better to set the temperature at 120 degrees, other says lower the temperature will increase the risk of pathogens growth.

Ways to solve this dilemma 

Every action there is equal and opposite reactions, so this problem also has a useful alternative. If you set priority on the risks of growing bacteria and also want to save your child and old family members from scalding, you can place an anti-scald device. Now you can set 140 degrees to kill harmful pathogens, and the anti-scald valve will save your family members from burning.

How to Adjust Water Heater Temperature

Also, you may change your old water heater with new instantaneous or tankless one. The on-demand water heater has a digital temperature controller with a monitor. So you can set temperature as per your demand, and it is not so much expensive as you consider the savings for a year.  Top of that it is environment-friendly also.

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