Can You Fill a Hot Tub with Hot Water?

Can You Fill a Hot Tub with Hot Water?

Can You Fill a Hot Tub with Hot Water?

It is indisputable that hot tubs use loads of power, and it would be a great idea to save some money in power if you had the idea how.

Consider, for instance, the fact that it might take up to 24 hours for a hot tub to gain the right water temperature from cold.

Consequently, it appears like a brilliant idea to fill your hot tub with hot water so that you do not have to use too much power and wait too long.

So, the concern is, can you fill a hot tub with hot water? Well, Yes.

This might save you a lot of time and money. However, it is not recommended to do that. There are risks involved in this since you might put too hot water.

In a too-hot-water scenario, the hot tub’s shell might be damaged.

Again, there is the risk of invalidating the warranty since some household hot water supplies will have water softeners that, once used in the hot tub, invalidates the warranty while others have scores of bacteria as well as debris in them.

Consequently, the risk is too high, and you will want to fill the hot tub with water and let it do the heating.

Hot tubs are not designed for temperatures beyond 40 degrees C. On the other hand, a domestic water tank has a minimum heat recommendation of 60 degrees C.

This means the minimum temperature to get hot water from a domestic water storage tank when heated is already too hot for the hot tub.

If you get this too hot water and put it straight to your hot tub, you start on an already wrong foot as you are 20 degrees C higher than the maximum that the shell should take.

Since the shell is not designed to ensure such high temperatures, it will most likely break. Unfortunately, repairing a hot tub’s shell is not a cheap affair.

Remember, you cannot go to the manufacture as this automatically invalidates the warranty, and therefore, you are alone in trying to fix this.

Will I Void My Warranty I Fill My Hot Tub With Hot Water?

Yes.Your warranty will be invalidated when you fill your hot tub with hot water. But you will have more serious problems than this! One of the problems comes with soft water.

Since many household hot water systems use water softening filters, their water is softened as it heats up.

When this hot softened water is put in a hot tub, there will be damages that your warranty won’t cover.

Again, if the water is too soft, it will cause corrosion on your hot tub’s internal working parts. If it can’t get this done due to the hardness of the parts, it will leave calcium deposits.

Can plug and play hot tubs be used in winter?

But you might still want to use hot water from other household appliances to fill your hot tub. Peradventure this is the case.

Ensure that you check for calcium hardness as soon as you are done filling the tub. After this, you will be better off making any adjustments and corrections from the levels you get from your test strip.

Another concern when filling a hot tub with hot water is the temperature cut out.

If the water is too hot, and this is more likely, your temperature will trip and be cut out on your heater. Consequently, the hot tub will not have self-protection from excessive temperature.

Additionally, the hot tub’s internal mechanisms will stand at a risk of being damaged.

As long as the water is too hot, that means temperatures above 40 degrees C; much damage can be caused on the hot tub’s internal mechanisms.

In addition to damaging the internal mechanisms, the shell itself might get damaged in the process.

One of the hurdles you will find on the way you attempt to fill your hot tub with hot water is its water system capacity.

Let’s assume that you have an average hot water system with a hot water tank, your tank holding about 180 litres of water.

Assuming that you have a combination boiler, it might produce between 10 and 20 litres of water per minute if it continues to flow.

Now your hot tub might require between 300 and 500 litres.

If the boiler’s temperature is set at 40 degrees C to prevent damaging your hot tub, you will need about three more full tanks or about one hour to fill with a continuous flow boiler.

I am just trying to think and calculate.

The idea of safely filling your hot tub with hot water is becoming too complicated! And how much money do you think you would save by boiling water this way?

Additionally, is it faster? I know you have the answers to these questions, and you don’t want to go that way.

Is It Possible To Heat My Hot Tub Faster?

Yes. This is practically possible. Many people have this concern after they buy their hot tub or after refilling it.

Indeed, you might even be looking for ways to get your hot tub temperature above 104°.

I will limit myself to other issues and avoid talking about this due to the risks involved with soaking in water whose temperature is beyond 104°.

Again, if a warranty still covers you, you will void your warranty if you tamper with the high-limit sensor.

However, all is not lost. You can still get hot water from your hot tub faster.

The first thing you need to do if you want hot water faster is to use your hot tub cover!

If your hot tub is uncovered, cold exposure from the outside delays your hot tub attaining the required temperature.

Can You Fill a Hot Tub with Hot Water?

One thing you need to appreciate about the cover is its insulation. Because of this insulation, it can keep the temperatures trapped inside for effective re-circulation with the water.

Again, ensure that you leave your hot tub covered anytime you are not soaking in it to avoid heat loss.

Jets have also been found to be effective in helping your hot tub to heat water faster. When you turn on the jets, the water circulation is improved, allowing more even heating of your water.  

With jets running, there will not be any pockets of cold water in the hot tub. This, coupled with the cover in place, you will find that your hot tub uses much less time to heat your water.

Additionally, you can install a more powerful heater. This is accepted by many manufacturers, and it is easy to replace a heater.

However, you will need first to conduct some research on hot tub heaters so that you buy the best suited for your hot tub.

Once you install the best suited for your hot tub, it will effectively cut down on the time you had to wait for that water to get hot.

Hot tub heaters are relatively cheap, retailing at less than 200$, ranging from 4kW to 6kW.

Can I Use Insulation To Prevent My Hot Tub From Losing Heat?

Yes. Many cheap/Less expensive hot tubs have poor insulation behind the panels and under the tub.

Therefore, if you want to increase the efficiency of such hot tubs in an inexpensive yet easy way, you can strive to register a reduction of the heat lost by the hot tub.

This is achievable when you add insulation. The default method used by hot tubs for heat insulation is spray-on foam and fibreglass boards.

The latter is around the shell, while the former is around the jets.

You can buy a waterproof thermal energy heat shield, cut it to size, attach it to your hot tub panels, or even place it under and around the shell.

This will be a quick and inexpensive heat insulation upgrade. One extra thing that it does is act as a noise dumper, reducing the noise that comes from the hot tub’s filter cycles.

Alternatively, you can also use a thermal blanket to heat up as long as you are not soaking. What a thermal blanket does is sit on your hot tub’s water surface.

This, coupled with the hot tub’s cover, is an effective way to minimize heat loss from your hot tub significantly.

If your cover wants, it will be complemented by the thermal blanket.

Luckily, you can purchase these cheaply from online stores or any hot tub dealership.

As you search for a hot tub to buy, it is critical to ensure full-foam insulation. Peradventure you buy a hot tub that lacks proper insulation, heat generation will be a struggle, reducing its effectiveness.

Can I Reduce The Time My Hot Tub Takes To Heat Water?

Yes. It is possible. But to do that, it is important to identify the reasons behind your hot tub taking longer to heat or losing heat too fast.

The first issue is the garden hose temperatures. While many people use a garden hose to fill their hot tub with water, much variation exists in garden hose’s temperatures.

Several main factors affect the temperature of your hose’s water. First, the source of the water is a factor.

All the same, garden hose temperatures oscillate between 50° and 75°. This is a great range, considering that water heats at 3 to 6° per hour in hot tubs.

Where precisely within the 3 to 6° range depends on the power of your heater.

Therefore, if your hose starts at 50°, you have an extra 4 hours, regardless of how powerful your heater is.

On the other hand, you will have an advantage if your hose has 75°.Therefore, identify a hose with a higher temperature and make always use it.

Again, if your cover is off when trying to heat your hot tub, it might take too long to heat up.

It is essential to ensure that your hot tub cover is in place when heating your hot tub water.

On top of this, your cover must also retain the heat so that you will be able to maximize your hot tub’s effectiveness.

A cover should fit tightly, and the flaps should be folded down, going around the hot tub’s edge.

Remember, the air that is outside your hot tub works against its efficiency.This means that your hot tub’s heater strains more if you lose heat through a poorly fitting cover.

Since an excellent fitting cover will also keep the generated heat inside the hot tub, it is critical to ensure that you have a properly fitting hot tub cover that should also be in good shape.

Can Jets Reduce My Hot Tub’s Heat Effectiveness?

Yes. Jets impact your hot tub’s heat effectiveness. If some jets are closed, there will be issues with your hot tub heating water.

As long as some jets are not on, it will take longer for your hot tub to heat up. Since jests improve water circulation, not having their results in reverse, water takes longer to heat up.

Are Saltwater Hot Tubs Better?

This is the same case, even with partially closed jets. However, there are other times that the heat might be faulty and therefore work improperly.


You can fill your hot tub with hot water, but it is not advisable.

There are several risks associated with this practice, and you may end up breaking or crack your hot tub’s shell, although other damages may occur.

Still, water from other heating appliances might be soft, and these would void your warranty if put in your hot tub.

Although it might seem expensive, it is best to fill your hot tub with cold water and wait for it to heat up. However, you can speed up the process if you use a hot tub cover.

This is because a hot tub cover works to retain heat inside while ensuring the cold remains outside by sealing the airflow.

An investment in a powerful heater is another way you can reduce the time it takes to heat your water.


Hi! I' am Tom. I was a manager in one of the biggest stores for over 10 Years, am also an SEO by night. I don't like to call myself a blogger; they are very analytical, do email marketing, and know all SEO stuff. I faced many questions from customers about different products, and there was hardly any help on the internet. After learning all the things about these products as a manager the hard way, I decided to start a blog and help other people.

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