Hot Tub Not Heating? 5 Important Things to Look For

By James Brockbank •  Updated: 01/30/21 •  11 min read

Why is my hot tub not heating up?

Hot tubs might not heat because the heating element is not working, the thermostat is not reading properly, low water flow, a high limit switch, and electrical problems are caused by low voltage or improper wiring. Each problem requires careful inspection.

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My recommendation for an immersible heating element is the LIVEBAY Immersion Water Heater if you need one to help heat your hot tub.

I know how frustrating it could be when things don’t go as planned. But it is better to solve the problem than to just rage about it.

If your hot tub is not hot, try our troubleshooting guide below. It is possible that the problem is minor and takes only a couple of minutes to solve. Hope that it is the case so that you can go back to enjoying your hot tub.

If your problem is simple, you will definitely find a solution here.

Also, check out our article on how long it takes to heat your hot tub for more information.

Let’s get started!

Hot Tub Not Heating? 5 Reasons Why

Most of the time, the problem lies in the corrosion of parts. Corroded heater elements and corroded temperature sensors are on top of the list. The reason is that most of the parts in a hot tub are made of metal, and metals do corrode, especially in low pH environments.

When you add sanitizers to disinfect the water, the pH of the water changes. Thus, it is necessary to maintain the pH under normal ranges so that your hot tub lasts for a longer time.

1. Hot Tub Heater Element Not Working

This is the most crucial step and must be done correctly as it might cost you hundreds. The heater unit might be shorted or scaled due to the use of a salted sanitizer.

For checking a short circuit, you will need a multimeter. Set the meter to ohms to measure the heater resistance. Connect the meter wires to the heater connections. It should display a value between 9-12 ohms as resistance is low to allow a high current to pass. But if the resistance is higher than that or the meter shows infinity, it needs to be replaced.

Scale can build up on the heating element, thus hiding the element. If the heating element is not in contact with the water, the heating will reduce. It is essential to keep the heating element clean. The scaling is mainly due to salt sanitizer, which causes different chemicals to build upon the heater element.

Scaling is a significant problem where the water is hard. You can reduce your hot tub’s scaling by adding some water softener to reduce the number of minerals in it. Wrong chemical proportions can cause the process of scaling to increase too. Always use the amounts of sanitizer as specified by the manufacturer.

2. Thermostat Problems

Your thermostats could be sensing the temperature wrong or could be corroded. As thermostats have changed over the past 30 years, you could be using old mechanical thermostats or meters.

If your hot tub has a meter or a mechanical thermostat, you can test whether it is faulty. These thermostats are mostly just screwed in the hot tubs and are easy to detach. You can check if the sensing bulb is corroded or the tip of the capillary tube is scaled. Or you can just replace the thermostat as they are inexpensive to buy.

Most of the thermostats are being replaced by temperature sensors, which are electronically controlled. All the sensors are connected to the main circuit, which keeps your whole hot tub in specified ranges.

A probe is used to detect the temperature of the water. One end is connected to the temperature sensor, and the other end of the probe is thrown into the hot tub. It is possible that the hot tub end of the probe has dirt on it, or it is just rusted.

You can pull out the probe and check it with a known temperature. If the temperature is shown is not right, that means it is a bad temperature sensor. You should replace it with something of high quality.

hot tub not heating

3. Low Water Flow

The hot tub heaters only work if there is adequate water pressure. The water cools down the heating element by getting heated up itself. If the water pressure is not sufficient, then a switch turns the heater off. This switch is called the pressure switch. A pressure switch must sense the pressure and keep your heater safe.

So, check for the possible reasons that could cause the water pressure to decrease. The most common reasons for the low water pressure include clogged water pipes, blocked pump impellers, or closed valves. Unclogging might release the water causing the water pressure to increase. The heater will start working again when the water pressure is regained.

If the problem still remains, then try checking the pressure switch. It is possible that the pressure switch is faulty and is not sensing the pressure right. Connect the two wires, connecting the heater to the supply, by a jumper wire to bypass the switch. If the heater working, replace your pressure switch. Some pressure switches have a knob to adjust the water pressure too. So, check if it is set at the right pressure.

In some older hot tubs, flow switches are also used. When the water flow is adequate, two metal plates come into contact and complete the circuit. These metal plates are separated by a spring, which gets compressed when water passes through the switch. The flow depends on the spring used and thus cannot be adjusted.

You can test the flow switch by bypassing it with a jump wire. If the heater starts heating correctly, then change the flow switch. These switches are usually just screwed in the pipeline and thus are easy to install. Flow switches are inexpensive to buy too.

4. High Limit Switch

High limit switches are basically temperatures sensors, but they don’t sense water temperature. Instead, they sense the heater coil temperature. Their purpose is to warn you if the heater is on the verge of being melted or they just cut the heater power.

Hot tubs using advanced thermostats will display an HL error code on the screen. If this signal is not going away, that means you have to replace it.

In older hot tubs, a red light comes on if the high limit is reached. Then you press a reset button to make it run again. The high limit switch may be broken. If the red light is showing, but the heater is fine, it is faulty and needs to be replaced.

In some cases, the high limit switch fails to tell you about the high heater coil temperature. The heaters melt and get damaged. It is important to always keep checking your sensing devices to make sure that they work correctly.

5. Hot Tub Electrical Problems

Apart from these primary problems, there are some little problems too. These are uncommon problems but are easy to solve.

Check for Fuses

Fuses are commonly used on devices that use large amounts of current. It is possible that a fuse on the control board is blown and is not letting the current pass through the heater. So check for these and replace them.

Proper Insulation

More heat could be leaving the tub than it is being added to the tub. Proper insulation of the heat tub is necessary, but unfortunately, many people don’t find it important. Keep the spa covers on. Replace them if they are broken so that heat is not being wasted.

Even if your hot tub is working g properly, it is necessary to minimize the heat losses to save on the running cost. Insulation is an essential factor to consider if you run a spa.

Tripped GFCI unit

A GFCI – a Ground Fault Circuit Interrupter – is a circuit breaker that cuts the electric supply within 1/40 of a second in case of a short circuit. It works by comparing the currents going to and coming from the hot tub.

When GFCI is tripped, a reset button comes out. Push this button to release the current. You can find this button on the GFCI unit.

Chewed or crossed wires can also cause the breaker to cut the supply. Check the cables for possible contact. Replace the cables if you find a defect. Contact a licensed technician to put the wiring as this can be dangerous to the bathers’ lives.

Door lock open

Many of the modern spas use door switches to prevent the excessive running of the hot tub. Opened doors waste the heat. The door switch turns the heater off if the door is open. Check if the doors are tightly closed before running the hot tub, or check the door switch by bypassing it with a jump wire.

Resetting Your Hot Tub Heating Element

Resetting the hot tub has proved to be a useful solution if the water is not heating up. Resetting the hot tub restores the company added parameters for the high limit switch, pressure switch, and thermostat.

The resetting method is different for different hot tub models, but I will talk about the technique that works for most hot tubs. If this procedure is not working for you, try to find the right way of resetting the hot tub on the manual. Or call your hot tub dealer.

Step 1: Turn the hot tub off from the breaker. After this, find the red high limit reset button. It is usually located on the heater.

Step 2: Press this button, and if you hear a click sound, it has reset.

Step 3: Turn the hot tub supply on and see if it has started working. If there is no power, check the GFCI outlet, which might have tripped due to a large current. Reset the GFCI outlet to release the current.

Step 4: See the operation of the hot tub again. If it has tripped again, the problem lies in the heater element. The heater element is shorted and is allowing a large amount of current to pass through. Replace the heater element to fix this problem.

Hot tubs with digital control units are usually reset by pressing and holding the temperature high and low buttons simultaneously. If you don’t know how to reset the hot tub, then the manual should help.

If you are lucky enough, then the resetting should make the hot tub work again.

How Much Does It Cost to Replace My Hot Tub Heating Element?

Many people ask that “how much would it cost to fix my hot tub.” But it is as senseless as asking someone how much does it cost to fix a car. Hot tub problems can cost you as low as $100, and the cost can rise to $500.

But I are not going to talk about all issues in this short article. The following text covers the costs required to replace a hot tub heating element.

I recommend the Balboa Heater Tube Assembly and products like it to replace conventional hot tub heaters.

My recommendation for an immersible heating element is the LIVEBAY Immersion Water Heater if you need one to help heat your hot tub.

Do It Yourself

If you think you are capable of doing it yourself, then it is excellent. The heating element can cost you $30, or if the tube and surrounding equipment are to be changed, the total cost would be $120. It really depends on the brand you are buying. High-quality equipment can cost up to $320.

Call a Pro

Not comfortable doing it yourself? Call a professional. Although it depends on the hot tub model is to be fixed, but on average, it can cost between $300 and $750.

If you are a spa owner, you should have a basic knowledge of hot tubs. This will make your business more profitable.

Hot Tub Not Heating: Conclusion

hot tub not heating

As you have seen above, most of the problems can be solved by yourself. There are a few cases where professional help is required. Try all of the troubleshooting methods, as solving even the smallest problems can make your hot tub run again.

If you are not sure about what you are doing, then this is the right time to call a pro. The combination of water and electricity can be very dangerous. It can even cost you lives.

With this information, I hope that your hot tub starts to heat again.

Check out this great article about some great hot tub benefits!

I hope you found this article on your hot tub not heating helpful.

Thanks for visiting

James Brockbank

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