Hot Tub Water Not Heating Up? (9 Reasons & Fixes)

If you turned on the hot tub, and the hot tub water doesn’t get hot after a period of time, then you might have a hot tub heater problem. So, why is your hot tub not heating up?

Different reasons could hinder a hot tub from heating up. It could be a burnt-out heating element, a glitch with the circuit board, a pest problem, a low flow issue, a faulty thermostat, wrong settings, or even low power voltage.

With so many possibilities, the most important step is to figure out the cause of the problem. When you narrow down the possibilities and figure out the cause, you can decide on how to fix it.

Why is The Hot Tub Not Heating Up?

If your water gets heated to the required temperature, then the heater is working. If the water isn’t hot, too hot, or not hot enough, then chances are that the heater is not working well. This could be happening for different reasons such as:

1. A Low Water Flow

The heater in the hot tub needs enough water around it to work. If the heater isn’t getting enough water, it would shut off and it wouldn’t heat the water.

A low water flow is likely caused by filth and dirt particles that block the water filter, the drain, or the pumps.

2. A Wiring Problem

A faulty wire could be the cause of the heater problem. Most times, there is a wiring problem because rodents have chewed the wires in the hot tub causing the heater not to work. A melted wire can also be the cause of the problem.

3. A Problem With the High Limit Switch

The high limit switch is a feature on the hot tub that prevents the water from overheating. The switch plays a regulatory role in the hot tub. A faulty high limit switch will cause the water to get too hot or hotter than required.

Related Read: How Long Does it Take to Heat a Hot Tub?

4. A Damaged or Wrongly Fixed Cover

Hot tub covers are designed to fit perfectly on the hot tub. If the cover isn’t placed correctly or the cover is damaged, it would result in heat escaping the hot tub and thus, you will have water that isn’t heated properly. This can also overwork the heater.

5. A Faulty Thermostat

A faulty thermostat can cause heating problems. Always check the thermostat to ensure it’s in good condition.

6. The Weather

If you live in really cold environments and you leave your hot tub open with water in it, the cold weather can cause the hot tub to freeze up. This can result in a damaged hot tub or a tub that has heating problems.

Any of these factors or a combination of more than one factor could be the cause of the problem. It’s important to figure out the precise reason or reasons your hot tub isn’t heating up well so you can take the right steps to rectify the issue.

7. Spa Heater Not Running Long Enough

Depending on the hot tub model you have, the water can get heated up to 1-3 degrees per hour. If you just turned on the hot tub, then you have to wait a couple of hours until the hot tub water gets hot.

You also have to let the hot tub run all the time, even on the days you won’t use it. If you do that, the hot tub water will always be hot and you won’t have to wait for it to re-heat.

8. Filters Are Dirty

We explained earlier that if you have a low level of water flow then that can make the heater burn. If you have a filter problem most of the time you will get some error codes (FL FLO, FL1). But, sometimes you don’t get the error code.

So, remove the filters and see if the water flow improves. If the water flow is improving then you have clogged filters and you need to clean/replace them.

9. You Just Filled Up The Hot Tub

If you just filled out the hot tub, then you need to wait at least 1-3 days until the water heats again. As mentioned earlier, you have to let the heater work every day for 4-8 hours to keep the water warm.

How Do I Know if My Hot Tub Heater Is Working?

A heating element will burn out quickly if there isn’t enough water around it. The outer casing of the heater might also be cracked or corroded due to the acidity of the water. But, how do you know if the heating element in your tub is bad?

To know if the hot tub heater is working, you should remove the side panel and see if the heater is getting power. You can also touch the side of the heater and see if it’s hot. If it’s hot then it’s working. 

If everything is good, but the water isn’t heating then you should also do these:

Test The Heater

You need to test the heater with a multi-tester or test meter that will be set to read in “ohms.” You will place a probe on the test meter to each screw on the heating element.

If the heating element is bad, it will give a very high reading or no reading at all. That means the heating element is either overheating the water or not heating it at all.

The normal reading of a hot tub heating element is between 10-12 ohms. Anything less or more than that will cause you to repair or replace the heating element.

Do a Regular Check Of The Whole Heating System

To keep the heating element in good condition, you are required to conduct a regular check and due maintenance on the whole heating structure. If you find out enough water isn’t getting to the heating element, then you should check the water filter.

Check For Dirt in Filters

It is possible dirt particles have clogged the water filters making it difficult for water to reach the heating element. This can cause it to burn out due to dryness. The heating element can also get corroded due to the effect of the sanitizers and chemicals used to treat the water.

Check the Hot Tub Chemical Levels

Sometimes, if you use hard water for your hot tub, then that can lead up to a hot tub scale. The hot tub scale prevents the hot tub heater to reach its full potential, and it can cause failure.

It’s best to check your chemicals levels. Keep the pH levels at 7.2-7.5, and the alkalinity levels to 70-80ppm.

How To Reset a Hot Tub Heater?

Sometimes, all you need to do is to reset the hot tub heater and it will start working again. But, how do you do that?

Most of the hot tub heaters have a reset button. The button is usually located on the control pack. Push the button and the hot tub heater will reset.

But, some hot tub models make it hard to find it. So, here’s what you should do:

  • Turn off the hot tub
  • Find the high limit reset button – You can check your manual to know the exact location of the button. But, it’s usually on top of the heater.
  • Press The Button – Once you press the button, you will hear a sound. Keep the hot tub off for at least 1 minute.
  • Turn On the Hot Tub – Once the hot tub has been turned on, test the hot tub heater.

Should You Replace Your Heating Element & How Much Does it Cost?

If the heating element in your tub is damaged beyond repair or you have repaired it many times, then it’s time for a change.

The price to change the heater varies depending on the hot tub model you have, the price of the heating element, if you need to change just the heating element or the whole heater, and the cost of hiring a professional if you do hire one.

This is not a DIY task if you are not vastly experienced. A poorly replaced heater can cause a whole lot of damages to the hot tub and can be life-threatening too.

To change the heating element by yourself, you would spend about $30-$60 depending on the cost of a new heating element, but if you hire a professional, it can cost a few hundred dollars.

Related Read: How To Reset a Hot Tub Control Panel?

How to Heat Hot Tub Without a Heater?

A heater is the most convenient and safest way to heat a hot tub, but it isn’t the only way. What happens when you want to use your hot tub urgently and you find out the heater is damaged or burnt out? You can use one of the following methods.

1. Let Nature Assist You

You can use the sun to heat your hot tub by placing the hot tub under the heat from the sun. Though this is going to take so much time, it can work for you if you live in very hot weather conditions.

2. Rent or Buy a Mobile Heater

There is a wide range of spa heaters out there that can help heat the water in your hot tub in the absence of a functioning heater.

As a safety precaution, do not go for water heaters more than 180k BTU for inflatable hot tubs, and for regular hot tubs, keep it between 200k BTU and 250k BTU to prevent damage to the hot tub.

3. Pay to Have Your Hot Tub Heated

There are dozens of small and large-scale hot tub companies that render services such as heating your hot tub for you.

Though the heated water wouldn’t be hot for too long since there is no heating element to keep it at the required temperature.

It’s important to note that none of the methods above is a substitute for the inbuilt water heater that comes with your hot tub. If the heater is faulty, contact help to fix or replace it. 

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