Hot Tub Not Heating Up

• Check for Error Messages: Most modern hot tubs can give error codes if something is wrong. Before continuing, try looking for any error codes that might explain the issue.
• Check the set temperature at the Control Panel: If you've recently started using your hot tub after having it drained or winterized, you must bring it back to temperature. When in use, the normal temperature should be between 100 °F and 102 °F (37.78 °C to 38.89 °C).
• Power Cycle your Hot Tub at the GFCI Breaker: A simple restart can resolve temporary issues with just about any device, and hot tubs are no different. Now, every spa is different, and you might want to refer back to your hot tub's owner's manual for specific instructions, but most hot tubs will need to be powered off at the GFCI Breaker. Switch the breaker off for 10 minutes, switch it back on, and see if the temperature increases.
• Check for Blown Fuses: Check for blown fuses: Power spikes, surges, or other incorrect voltages can cause your hot tub’s fuse to blow. Check to see if the fuse on your hot tub’s control board has not been blown.

A hot tub uses a pump to circulate water through a heater and back into the tub, maintaining a consistent, warm temperature. If there's no flow or the flow becomes blocked, the water can't pass through the heater, meaning the heat can't be distributed correctly. Typically, this shows itself as the error code FLO.

• Fill your Hot Tub all the way: If the water level in your hot tub is too low, water won't circulate through your system, causing your heater to become overloaded and switch off. Check your manufacturer’s recommendations for the proper water level.
• Clean or Replace your Filters: If your hot tub's filters become blocked with dirt and debris, water will not be able to flow through your system. Properly clean your hot tub's filters, or replace them if you notice any damage.
• Remove Air from the Pipes: If you've had to drain and refill your hot tub, Air can become trapped inside your system, leading to an airlock. Removing your hot tub's filter and turning the jets on for a few seconds to clear out any airlock.
• Unclog your Pipes: Clogged water pipes can also prevent your hot tub from heating up properly. You can clean your pipes using System Flush or another hot tub flush product.

If your pump isn't running correctly, then this can prevent water from flowing throughout your hot tub, causing improper heating. If you notice any of the following from your pump, you might need to source parts, or in the case of older hot tubs, find a replacement pump.

• Listen for Pump Failure Symptoms:
  • The motor is humming but not turning. This can indicate a frozen shaft, bearings, impeller, or defective starting capacitor.
  • Winding noises from worn bearings. If the bearings on the impeller become worn, this can impact the pump's effectiveness and prevent water from flowing through your system.
• Look for leaks under the pump. Bad or damaged gaskets can cause your pump to leak water and prevent it from functioning normally.

If you are not hearing anything from your pump, you should make sure that it is getting power.

Many hot tubs have several different sensors that help keep both the hot tub itself and users safe. If one of these sensors breaks, the hot tub will shut itself down as a safety measure. Check the following sensors.

• Pressure Switch: Pressure Switch: This is typically screwed into the heater chamber and detects when the water pressure drops below a certain level, safeguarding the heater from overheating. This switch should function properly if your hot tub has the correct water level and flow. You can bypass the switch using a jumper wire to test if it is malfunctioning.
• Flow Switch: Flow switches function similarly to pressure switches but are triggered by water flow. When the water flow is strong enough, the two internal paddles are pushed together, completing a circuit. Conversely, when the water flow is insufficient, the circuit is broken. Much like a pressure switch, a jumper wire can be tested by bypassing it with a jumper wire. These switches should be inspected for scale, corrosion, or bent paddles.
• Thermostat: A thermostat is a device that automatically regulates temperature. Most newer hot tubs will use temperature sensors connected directly to the circuit board, controlled by the hot tub's control panel. Inspect the temperature probe for damage, and ensure it is plugged into the panel snugly, along with the connection between the probe and the board. If your hot tub was made before the 2000s and has s thermostat knob, check that the internal thermostat isn't internally fault and that the sensor bulb has not become corroded.
• Limit Switch: High-limit switches are safety switches that prevent your hot tub's water from becoming too hot. When they cause a heater problem, high-limit errors will normally display as an HL code or OH code. High-limit tripping can also be due to low water flow, incorrect voltage, a malfunctioning element, loose wire connections, damaged wires, or a faulty high-limit switch.

If your hot tub's heater isn't getting power or has become damaged, it won't be able to heat your water. These heaters work similarly to the heating element in an electric water heater, and can burn out quickly if operated without cooling water surrounding them.

• Check that there are no shorts in the heater: You can use a multimeter set to ohms to measure the resistance of your heating element. Typical good elements will display 9 to 12 ohms, but if the resistance is significantly higher, the heater must be replaced.
• Check for Scale Buildup: When a spa element develops scale on the outside of the element, it will reduce the element's heat output, and could eventually lead to element failure. If you notice any cracks along the heating element's outer casing, replace the element.