What Is the Best Temperature for a Hot Tub?


Selecting the right hot tub temperature comes down to a lot more than personal preference. Your age, sex, and health status must be considered in order to remain safe. So how do you know what’s best for you?

Most hot tub owners enjoy a temperature between 98-100°F (36-38°C). While temperatures up to 104°F (40°C) are safe for healthy adults, the temperature must be lowered for the elderly, vulnerable, pregnant, and children to ensure their safety. Seasonal changes usually require the temperature to be adjusted.

This article is going to break down in detail which temperatures are most safe, how to prepare for seasonal changes, and what to do when the spa is left idle. I’ve also included some additional health and safety tips that every spa user should employ.

Safe temperatures based on age and health status

A safe and comfortable hot tub temperature is dictated by who is using it and each person’s personal preference. As such, the best way to find a safe temperature is by experimenting with the entire family present. 

Once you find a temperature that everyone is comfortable with, it’s better to maintain that temperature. Raising and lowering the heat continuously can increase operational costs.

Healthy adults

There is no right or wrong temperature for healthy adults. The temperature does depend purely on personal preference. While some enjoy the maximum safe temperature of 104°F (40°C), many find a hot tub to be more comfortable between 98-100°F (36-38°C).

You’ll find that most spas come with a factory default setting of 100°F (38°C). However, I recommend adjusting your hot tub to the same temperature as the average human body (98.6°F/36°C) is a good place to start.

As you soak in the tub, gradually increase the temperature to a comfortable level where you don’t feel overwhelmed. Generally speaking, women are more sensitive to cold than men, so they tend to prefer the water to be slightly warmer. This might mean you have to find a compromise with your bathing partner.

For health and safety reasons, modern hot tubs have a maximum temperature of 104°F (40°C). According to the United States Consumer Product Safety Commission, anything above 104°F is highly dangerous.

Temperatures of 106°F (41°C) and higher can lead to heatstroke. Heatstroke is when your body temperature rises as a result of it no longer being able to regulate its internal temperature.

Despite the fact that your hot tub likely maxes out at 104°F, you should still exercise caution when raising the temperature as you may be unaware of an underlying health condition.°

For temperatures between 97 and 104°F (36-40°C), limit your bathing time to 20-30 minutes. If you use your hot tub for exercise, you should reduce the temperature to 96°F (35°C) to avoid dehydration and overheating.

Elderly and vulnerable

Hot tubs pose health risks for the elderly and the vulnerable. Elderly or vulnerable persons taking medication must check with their doctor or consult a medical professional before using a hot tub. 

They should also start by using the spa for short periods of time. This means no longer than 30 minutes. Anything above this could lead to heat-related illnesses.

Elderly people with fragile skin should avoid soaking in water that is hotter than 102°F (39°C) because it can burn the skin.

People experiencing heart conditions or breathing issues should use hot tubs with extreme caution, or better still, stay away from them entirely.

The reason is that when you stay in hot water, your blood vessels expand, leading to pressure variations, which can cause dizziness or fainting for people with heart conditions.

Additionally, William KormosOpens in a new tab. of Harvard Men’s Health Watch advises against a fast transition from a hot tub to cold water because this can cause a sudden jump in blood pressure. Persons with high blood pressure (hypertension) should also be careful when soaking in spas.

According to a 2003 studyOpens in a new tab. by the University of Saskatchewan in Canada, it is only safe for hypertensive patients to spend 10 minutes in a hot tub. Anything more than 10 minutes can cause serious health problems.   

Pregnant women

Spending more than ten minutes in a hot tub can raise your body temperature above 101°F (38.3°C), which could negatively affect a pregnant woman and her growing child. 

Pregnant women should use hot tubs with great caution and for short periods of time. A 2011 studyOpens in a new tab. suggested that using a hot tub during the first trimester can result in birth defects. It’s advisable to consult your doctor before using a hot tub in the early stages of pregnancy.

The general recommendation is to avoid the hot tub throughout your first trimester. Your unborn child could be in danger even if you limit the time to less than 10 minutes. 

If you’re past your first trimester and have gotten approval from your doctor to use a spa, then you should limit your time in the spa to 10 minutes and avoid water temperatures above 95°F (35°C). Here are some additional tips to keep you and your unborn baby safe:

  • Give yourself plenty of time to cool off between sessions.
  • Avoid seating near the hot water jets.
  • Try to maintain your chest above the water. 
  • Avoid using the hot tub if you feel feverish.
  • Leave the hot tub immediately if you start feeling any discomfort.

Children

Babies and young children should stay away from hot tubs. The Centers for Disease Control and Prevention advises that children below five years should not use hot tubs. 

For kids over the age of 5, the maximum water temperature they can soak in should be 95°F (35°C) since they are less able to control their body temperature. 

You should always supervise your children while they’re using the spa. Never let them stay in the tub longer than 15 minutes at a time.

Temperature ranges based on seasonal changes

You can get the most out of your hot tub by adjusting the temperature according to the season.

Summer

Most people find that a water temperature range between 80 and 85°F (26-29°C) is ideal during the warmer months of the year. Experiment with temperatures within this range to determine what temperature is most suitable for you.

If you’re looking to cool down your spa quickly, turn on the water jets after reducing the temperature. The circulation of cool water can lead to a rapid decrease in temperature. 

Certain hot tub brands have manufactured special water chillers that enable you to use the hot tub cold. The chillers allow you to reduce the water temperature to 60°F (16°C), regardless of the ambient temperature.

Winter

The contrast in temperatures makes using a hot tub during the winter very enjoyable. You’ll most likely find that you want to set your hot tub a little warmer than your preferred temperature to make it more comfortable. 

Raising the temperature is also necessary because the winter breeze removes heat from your spa. A comfortable hot tub temperature for the winter period is 100-104°F (38-40°C).

Not only does this temperature keep you warm, but it also protects your tub as the heat prevents vulnerable parts from freezing up.

The best temperature when not in use

Depending on the ambient temperature and the insulation quality of your spa, you can cut your hot tub’s energy expenses by 10% for every 2°F (1°C) drop in temperature.

The general recommendation is to lower the temperature when the spa’s not in use by 10°F (5°C). While this might seem like a good idea, it amounts to a saving of less than $10 per month.

If you use your spa several times a week, it’s far more convenient to keep it at your preferred bathing temperature. 

If you use your tub once or less a week, then turning it down 10°F can help save on electricity and shouldn’t provide too much inconvenience.

If you’re not going to use your hot tub for two weeks, you can lower the temperature by 20°F (9°C) by turning on economy mode. 

Additional health and safety tips

Unfortunately, safe bathing temperatures are not high enough to kill the many bacteria that thrive in warm water. In order to kill bacteria such as legionella, you must ensure proper sanitization. Here are some other helpful tips to prevent a build-up of bacteria:

  • Ensure easy access to all mechanical and filtration components for routine and preventive maintenance and service.
  • Use line flush to get rid of any traces of biofilm in the plumbing.
  • Drain spa water every 3-4 months.
  • Disinfect the empty shell with a chemical cleaner.
  • Optional: use automatic feed and control systems to maintain a proper disinfectant residual.

Here is a list of best practices for staying safe when using a hot tub:

  • Avoid a hot tub if you have diarrhea.
  • Avoid ingesting spa water.
  • Shower or bathe with soap before soaking in a hot tub.
  • Follow the rules on the highest allowable number of bathers.
  • Don’t drink alcohol before or while using the hot tub.
  • Ensure the tub is properly sanitized.
  • Ensure the filtration system and pumps are working properly.
  • Adjust the water chemistry frequently.

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