A hot tub thermostat works to control the temperature of the water in the tub. Temperature issues may be related to poor thermostat calibration. Depending on the model you have, you can usually calibrate a hot tub thermostat yourself.

Tools and Materials

Thermometer
Allen key
Flat Screwdriver

Step 1: Check Water Circulation and Water Level

There are few items you need to before calibrating your thermostat. Water level and circulation can adversely affect temperature. Water circulation or flow helps regulate temperature by moving water around. This is achieved through the use of water jets and the filter.

Check to see if your filter is clogged with debris. This may be restricting water circulation, causing the tub to overheat. Also make sure all jets are performing correctly. Inspect the water level of the hot tub. Low water levels heat quicker and maintain higher temperatures.

Step 2: Checking the Temperature Probe

Another factor that affects temperature is the temperature probe. This is the device that tells the thermostat what the water temperature is. Find your hot tub's thermal well. Make sure the temperature probe is pushed down in the well.

Step 3: Determine Actual Water Temperature

Now it is time to verify the actual water temperature. To do this, turn off your hot tub's timer. You don't want it to come one while performing any tests. Turn the temperature of the thermostat all the way up. After allowing ample time for the water to heat, use a thermometer to test the water temperature. Compare the thermometer reading to that of the thermostat. If the thermometer is off several degrees from the thermostat, you may need to calibrate or replace the thermostat.

It is important to note that the Consumer Product Safety Commission (CPSC) regulates hot tub temperature. It can not exceed 104 degrees F. This is because of the health risks associated with increased body heat. Temperatures of 104 degrees F can cause heat exhaustion, heat stroke, heart attack, brain damage, and even death. This is why it is important to check your hot tub's water temperature often. Keep a water thermometer handy so you can compare the water temperature to the thermostat.

Step 4: Determining Calibration

Not every hot tub thermostat can be calibrated. Determine if your hot tub can be calibrated by looking at the back side of the thermostat. If a small Allen screw or flat screw is present, it is most likely used for calibration.

Step 5: Calibrating the Thermostat

Using the Allen wrench or flat screwdriver, turn the screw on the back of the thermostat one-quarter turn clockwise. This will increase the temperature calibration. Wait for the water to heat up. Now use the thermometer to recheck the temperature. Compare the results with the thermostat. If more heat is needed to calibrate the water temperature with the thermostat, turn the calibration screw another quarter turn. Repeat as necessary until your hot tub's water temperature matches the thermostat. If the water temperature does not satisfy the thermostat setting after calibration, you may need to replace the thermostat.