How does a spa heater work?

There is nothing better than soaking in warm water on a cold evening - and that is why the heater in your spa is one of the most important components!

spa heater

In this article we’ll discuss how a spa heater works and provide some troubleshooting steps if your spa is not heating up. We’ll also talk about the different types of heaters that are available, including pros and cons and the costs of different types of spa heaters.

We answer questions such as:

And more!

How does a spa heater work?

The most common types of spa heaters have an electric element encased in a tube. The water from your spa travels through the tube and gets heated as it passes across the element.

The warm water is then circulated throughout your spa by your circulation pump which moves the warm water evenly throughout your plumbing and out into your spa water.

Turning your jets on also helps move the warm water around evenly and keep the temperature even through all areas of your spa.

How do I heat my spa more quickly and efficiently?

If you want to heat your spa up in a hurry, follow these steps

  1. Leave the cover on while heating, so heat does not escape off the top.
  2. Upgrade your heater. If your spa is heating up too slowly, your element may be too small for your spa.
  3. Fill your spa with warm water. Instead of running cold water from a standard garden hose, you can run a hose from the hot tap inside your home so your spa starts with already warm water
  4. Run your jets. Turning your jets on while heating circulates the water and can help it heat up more quickly
  5. Heat your spa on a warm day. If you can wait until a warmer day your spa will heat more quickly and efficiently.
  6. Add insulation to your spa. You can also add insulation inside your spa cabinet which will help retain the heat and make it quicker to heat up and help your spa retain heat for a longer period.

How much does a spa heater cost?

Spa heaters start from around $400 and can range up to $1000 or more depending on the size and model of the heater unit.

Note that these days, modern spa heaters are packaged with a spa controller. If you have an older spa with a heater that needs replacing, now could be a good time to consider replacing your spa controller and heater with a more modern option.

How long does it take to heat a spa?

As a general rule, an average sized portable spa will take about 24 hours to heat up.

There are a few variables that will affect the heating time including the starting temperature of the water, ambient temperature outside, the desired temperature you want the water to heat up to, volume of water in your spa and the size of your heater.

All of these variables will affect how long it takes to heat your spa.

How long does it take to heat a swim spa?

How long does it take to heat a swim spa?

As a general rule we tell customers that their swim spa will take between 48 to 72 hours to heat up. Again, there are a number of factors that will affect the time that your swim spa takes to heat up as we mentioned above.

Does a spa pool heater run all the time?

Your spa heater does not run all the time. It only operates in heating mode when the water temperature in your spa drops below your set temperature. When this happens, then in modern spa systems, the controller can automatically sense that your water temperature has dropped below the set temperature and the heater will turn on again, until your water reaches your set temperature again.

When your water temperature is reached, the heater will turn off, saving you power and money.

Are spa heaters expensive to run?

In an average sized spa (2.3m x 2.3m) the heating system will draw 3kW of power and operate for about 10 minutes each hour to maintain the heat in your spa. This means it will operate for 4 hours per day.

Multiply 4 x 3kW = 12kWh x $0.25 (Cost of electricity) = $3 per day.

Read more about how much a spa costs to run.

How do I know if my spa heater is working

To determine if your spa heater is working, your should ensure that your spa is powered on, set your water temperature to around 34-38 degrees celsius (depending on your preference). Then replace your spa cover and leave the spa for around 24 hours to heat up. Then check your water temperature to see if it has heated up.

How do I turn on my spa heater?

You do not need to turn the heater on manually in most spas. In most modern spas, the spa heater is connected to your spa controller. It is automatically activated by the controller when you set your temperature. Your controller uses a senser to sense the temperature of the water. If heating is needed, the controller will automatically turn the heater on.

In older spas (20+ years old), your heater may not have an automatic control, which means you will need to turn it on and off manually - there will be a switch or button somewhere on your spa to turn the heater on.

If you are not able to locate the heater switch, you may need to get a technician to come and assist you.

Can you heat a spa with electricity

Yes you can heat a spa with electricity. Most modern spa systems do use an electric heater element to heat your spa. This is the most common type of heater used.

What is the cheapest way to heat a spa pool?

The cheapest way to heat your spa is with a heat pump. A spa heat pump can use up to 75% less energy than a standard heater - therefore saving you money on electricity.

Find out more about spa heat pumps

Can I replace my spa heater?

Yes. If the heater component in your spa stops working, then it is possible to replace it. In many modern spa controllers, the heater element is integrated into the controller unit. It is possible to replace the heater element in these units.

In older spa systems, the heater unit may be a standalone unit, or it may be incorporated into your circulation pump. (Pumps with a heater built in are known as a ‘hot pump’).

How do I replace the heater element in my spa?

To replace the heater element, you’ll need to follow these steps.

  1. Disconnect the power from your spa or turn of the main circuit breaker.
  2. Close the T junctions on both sides of the heater (to stop water escaping)
  3. Disconnect all cables
  4. Remove the heating unit
  5. Replace with a new unit (or if it is just a faulty element, you can just replace the element)*
  6. Install new gaskets and O-rings if the existing ones are worn
  7. Reconnect all cables
  8. Open the T junctions to let water back through.
  9. Turn the power back on
  10. Test

*In many cases, you may not need to replace the whole heater assembly, you can just replace the element.

heater element

How can I make my spa heater last longer?

There are three key things you need to pay attention to in your spa to make your spa heater and all the other components in your spa last longer.

1. Make sure your water is balanced

It’s important to keep your spa water balanced and well maintained. This means you should be testing the pH and alkalinity in your spa regularly (at least once per week). Ensure your pH falls into the ideal range of between 7.4 and 7.6 and your water alkalinity is in the range between 100-150 mg/L.

If your water balance falls outside of these ideal ranges, you’ll need to adjust it accordingly. Read our article on how to test and adjust your ph and alkalinity.

Ensuring your spa water is balanced will protect the heater components from corrosion and wear which could shorten its life.

2. Flush airlocks in your spa water system

Each time you drain and replace the water in your spa, it is important to remove any airlocks in your system. To do this, you’ll want to loosen the unions around the heater and pumps until a little bit of water dribbles out around those connections. When the water does drip out, this shows the airlocks have been released and water has completely filled your plumbing system.

This will mean the water in your spa is circulating correctly and there will be plenty of water flowing through the heater unit to stop it from burning out prematurely.

If there is not enough water flowing through the heater element it can get too hot, reducing it’s lifespan.

3. Clean filters regularly

The third step you need to take to protect your spa heater is to clean your spa filters regularly. If your filters are clogged by dirt, debris or grime, this will reduce the flow of water in your spa system. This can cause your heater element to get too hot.

In addition, you may find that your spa does not maintain its temperature as the water is not being circulated quickly enough to move the warm water evenly throughout your spa.

Got more questions about spa heaters?

Talk to us on live chat, or email us your spa questions and we'll be happy to help!

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