What temperature should a hot tub be?
Never above 40°C (104°F), says the U.S. Consumer Product Safety Commission (CPSC). It calls 38°C (100°F) safe for a healthy adult. Check the water with an accurate thermometer, because a thermostat can be off by as much as four degrees.
What is the safest hot tub temperature?
The U.S. Consumer Product Safety Commission (CPSC) says hot tub water temperatures should never exceed 40°C (104°F). It calls 38°C (100°F) safe for a healthy adult, and it suggests special caution for young children.
The King County public health hot tub guide (Seattle and King County, Washington) agrees on the limit. Its heading is that hotter is not better, and it says to keep the water no warmer than 104°F.
Why check a hot tub thermostat with a thermometer?
A thermostat can be wrong. The CPSC says hot tub thermostats may err by as much as four degrees. Its advice is to check the water temperature with an accurate thermometer before you get in.
The King County guide says the same. It recommends a high-quality shatterproof thermometer that reads in small steps, and it says to check the thermometer itself regularly. A thermostat set to 100°F could be holding the water as warm as 104°F. That is the reason to measure the water.
Do this every time you get in. The King County guide says the air around an outdoor tub changes how the water feels, so your own sense of the temperature is not a reading.
Does the air temperature change how the water feels?
Yes. The King County guide says the air around an outdoor tub changes how the water feels. On a hot or cold day, the water may seem warmer or cooler than it really is.
Its advice is to read the thermometer for the true temperature before you adjust the heater, and not to rely on your own estimate. The guide says this matters most for outdoor tubs.
Who should ask a doctor before using a hot tub?
The CPSC says people with a history of heart disease, circulation problems, diabetes or blood pressure problems should ask a doctor before using a hot tub.
The CPSC also warns against excessive drinking during hot tub use. The King County guide adds that children need supervision and that a hot tub should ideally never be used alone.
How does the One Model handle temperature?
Waterlab sits in the plumbing and reads pH, ORP and temperature. The app (Gecko in.touch 3) shows all three on your phone, so you can check the water before you lift the cover. The water pump runs 24 hours a day and moves the water through the filter, the ozone chamber, the salt system and the heater.
The limits above apply to every hot tub, the One Model included. Good Hot Tubs has not released the heater rating, the heat-up time or the range of temperatures an owner can set yet. For a second reading, the CPSC advises an accurate thermometer.
Before ordering, the team looks at your yard on a video call, and a local expert on Vancouver Island delivers and sets up the tub. Orders open January 1, 2027. Until then, you can answer ten quick questions on the site and ask for a test soak on Vancouver Island when you send your result.
Does a hotter tub make a better soak?
The King County guide says no. It says the soaking time should be shortened as the water gets warmer, and that for a long rest you should lower the temperature. It suggests trying different temperatures within the safe range to find what suits you.
That means the top of the range is a limit. A temperature of 38°C (100°F) is the one the CPSC calls safe for a healthy adult.
What else makes a soak safer?
The King County guide says to supervise children, and not to use glass or other breakable containers around the tub. It also says that, ideally, nobody uses a hot tub alone.
A local expert on Vancouver Island is the person to ask about the rest, and a One Model is set up on the Island for test soaks.
Questions
Is 104 degrees too hot for a hot tub?
40°C (104°F) is the limit. The CPSC says hot tub water should never exceed it.
What is 100 degrees Fahrenheit in Celsius?
About 38°C. The CPSC calls 100°F safe for a healthy adult.
Can you drink alcohol in a hot tub?
The CPSC warns against excessive drinking during hot tub use.
Can a hot tub thermostat be wrong?
Yes, by as much as four degrees, according to the CPSC. Use an accurate thermometer to check the water.
Sources
General facts on this page come from these public sources. Facts about the One Model come from Good Hot Tubs.
- CPSC Warns Of Hot Tub Temperatures. U.S. Consumer Product Safety Commission (CPSC).
- Staying Happy and Healthy in Your Hot Tub, sixth edition (PDF). Public Health, Seattle and King County.
Related answers
Is the One Model right for you?
Ten questions about your home and how you would use a hot tub. You see your result before you give any contact details, and you can ask for a test soak on Vancouver Island when you send it.