The 5 Most Common Hot Tub Heater Problems

A hot tub is not meant to be cold. Of course, a hot tub that doesn't heat is not fun for anyone.

When your hot tub or spa is not working properly, it can feel like there's no heat inside. This can happen even if the heater is working properly.

Below are some of the most common issues that arise when it comes to hot tub heater problems.


1. Low Flow

Dirty spa filter is often associated with a low flow issue in a hot tub or spa. If your issue still remains unresolved, you should perform an inspection to remove the filter.

Troubleshooting a Faulty Pressure Switch

A spa heater depends on the proper flow of water to operate. When the flow is too low, a pressure switch activates and the heating element stops.

Most pressure switches are tested by plugging the two wires together using a jumper wire. They can also be adjusted by hand with a thumb wheel or a small slotted screw.

Troubleshooting a Faulty Flow Switch

A flow switch is a type of switch that controls the flow of water in a spa. It works by pushing two paddles together to close a circuit. If the flow is too low, the switch will remain open.

Some flow switches can be tested by connecting the two wires together using a jumper wire.

Although flow switches are not adjustable, they often need adjustment. When using, make sure that the surfaces are free of scale and the paddles are not bent.


2. Thermostat Issues

The temperature sensor is used to control the hot water. The topside control panel is a remote control. In the past, most spas used solid state probes.

Many older mechanical thermostats have a capillary bulb. If this is the case, then it's time to check the unit's internal components.

For newer models, the temperature sensor is usually replaced. This component comes with a probe end that slips into a thermowell.

If the water temperature of your hot tub is not displaying properly, it could be a bad sensor. Having a good temp sensor is also important to prevent issues.


3. High Limit Switch

The high limit switch is a component of the safety circuit of a spa heater. Its purpose is to prevent an overheated spa heater from causing a malfunction or even a fatal accident.

Some hot tubs have two high limits. One is inside the heater and one is outside the heater. When the high limit gets too high, it will display as an error code.

High limit tripping can occur when the water flow gets too low or the wrong voltage is applied. It can also be caused by various issues.


4. Hot Tub Heater Element

A hot tub heater is similar to a water heater element, and it burns out very quickly if not connected to a cooling water supply. This component can also be tested to see if there is a short coating on the surface.

Use a test meter with a set of ohms to measure the resistance of a spa heater element. A good element should display 9-12 ohms.

A spa element can also develop a buildup from hard water or saltwater sanitation systems. This issue could cause the element to fail.

Since the elements resemble a stovetop coil, a new element is typically needed if the outer casing breaks.

For those with older spas, your spa heater element is typically housed in a steel chamber with unions. These components can be easily removed with a simple push of a button.

A multimeter or ammeter is commonly used for testing. When it comes to shorting, the meter does not have any activity on it.


5. Other Causes of Hot Tub Heater Problems

These are the causes of spa heater troubles that most people don't think about. They can be fixed quickly and easily.

GFCI Tripped

Look for the electrical outlet on your spa pack – the one with the red TEST button. If it's popped out, push it back in firmly.

Door Interlock Open

Many spas have a cabinet switch or spa pack cover switch to prevent operation unless the doors are tightly closed.

Spa Cover Needs Replaced

Warped, broken, and ill-fitting spa covers can allow heat to escape just as quickly as the heater adds it to the water.

Loose Wires

Connections must be tight and not oxidized. Chewed wires (rodents), melted wires, or crimped wires are also possible.

Blown Fuse

A power spike, surge or other incorrect voltage may have destroyed the fuse on a control board.


If you have any other questions about pool and spa products please do let us know - we are here to help!

Leave a comment