Can I add a Hot Tub to my Existing Swimming Pool?

Hot Tub In Swimming Pool

Can I add a hot tub or jacuzzi to my existing swimming pool? This is a question that many people ask me when they are looking to revamp or modify their backyard setup.

When it comes to adding a Hot Tub or Jacuzzi to your existing swimming pool, there are a number of things you need to consider. In this blog post we will explore everything you need to consider before you embark on such a project.

Hey, if you are looking for “less of the theory” and more of a case study, then click on the button to be taken to see “Joe from Michigan” and learn how, with my help, he added a DIY Hot Tub to his existing pool!

How Big is the Hot Tub or Jacuzzi Going to Be?

The first thing we need to look it is size. How big is the Hot Tub or jacuzzi going to be that you will add to your existing pool? This will dictate how many jets you will need to install. Remember, the maximum on a single pump is around 16 jets depending on the exact size of the pump, the head height and the flow rate of each jet.

How deep do you expect the Hot Tub to be? Most of the Hot Tubs that I build have a water depth of 900mm or 35.5″.

Hot Tub In Swimming Pool

How many people to you envisage the seating being for?

Do you want to arrange your jets into clusters or do you want to have them in a row around the middle of the back of the seat? Again, this is something to think about.

Do you want the Hot Tub to overflow into your Pool?

Most customers that want to add a Hot Tub to their Swimming Pool want it to be able to overflow into the pool. Looks great doesn’t it. Waterfall flowing into your pool. Just like you see in the resorts.

This is not a problem and the plumbing to do this just requires that there be a swimming pool return line into the tub section. This will allow the swimming pool return line to fill up the hot tub and then once full, it will overflow naturally into the pool.

Likewise, when people get into the tub, the water displacement that a person or persons cause, approximately 70 litres or 15.5 gallons per person, will also cause this to overflow. Not a problem at all as the return line from the pool will then fill the tub back up.

The problem comes if you want to have the temperature different to that of your pool. Think of it like this. If your cooler pool water is being returned into your hot tub that is heating up, it is going to hamper the heating of the water for sure.

It might never actually get up to temperature! We’ll look at heating in a separate section of this post.

What About Chemicals?

If you want to be compliant with guidance, Hot Tub chemical concentrations are different to Swimming Pool concentrations.

This is due to the usual differences in heat between a hot tub and a pool. Obviously, this is down to personal preferences here but if you are going to be overflowing your

Hot Tub into your pool and then refilling from your pool into your hot tub, keeping the chemicals at the different levels is not really going to be possible.

A potential solution to this is adding a chemical free UV System to your setup. This means you don’t need to worry about chemicals in the pool and the hot tub as the UV light will kill all bacteria.

UV is great as you cannot overdose on it. You don’t need to test the amount that is in the water, you simply select a system that can deal with the volume of water that is going through your pool and hot tub.

Can I Use My Existing Pool Plumbing?

The simple answer to this one is yes and no. You can use your existing filter and your existing pump to be used a circulation pump.

You can also use and you should use, your existing return lines to fill the hot tub and make it overflow (if that is the style you are opting for).

What you can’t do as I explain below, is use your pump to power the jets.

You have to be mindful here on not only the heating of the pool, but on all the other elements too. You are increasing the volume of the water that is going to need to not only he heated but filtered too. 

If you pool has been designed in a way that it is close if not on the limit of the filtration and heating capabilities of the kit you have in place, you are going to want to think about changing them and making sure that the ones you buy are sized correctly for the new total volume of water.

Can I Use My Pool Pump for the Jets?

Unfortunately, not. Pool pumps are designed to move large bodies of water through a filter and return the filtered water back to the pool.

They are not designed to force water under pressure through a jet. Also, generally a pool will have a circulation pump that will be less than 1HP.

A jet pump as a bare minimum will be 2HP. You also have to bear in mind that each jet has its own flow requirements. If you don’t have enough flow into the jet then it will now function correctly.

Therefore, when you are adding a Hot Tub to your existing swimming pool you need to put in a separate plumbing system for your jets.

You don’t need to filter this as the pool filter will do that for you. You should however, have two lower drains going into a single speed jet pump (if you are not heating the hot tub separately and a dual speed pump if you are) and then back out into your hot tub. It is a simple plumbing system that is needed to give you the result you are looking for.

What About Heating the Hot Tub?

Heating the Hot Tub separately from the Pool or to a different temperature from the pool is where it becomes a little tricky. You can’t do this on your existing plumbing without shutting off the overflow whilst your hot tub heats.

You need to have a separate heating circulation system if you plan to heat your pool and your hot tub to different temperatures. Once up to temperature, you can then change the valve so that it overflows again and is refilled from the pool; but you can’t heat and overflow at the same time.

I guess you physical can if you want to, but it is going to be counterproductive and cost you more. Remember, when you are using the overflow and returning water from the pool, you will be returning cooler water so the temperature will drop in the Hot Tub.

We are not talking huge amounts here but obviously over a period of time it will reduce the temperature of your Hot Tub. Logical I guess if you are returning cool water to the Hot Tub.

If you are going to heat the hot tub separately, then you are going to need to have a dual speed pump adding to the system. The low speed will be used for circulation and heating the tub. The hight speed will be used for the jets.

Hot Tub In Swimming Pool-2

Adding a hot tub to an existing swimming pool can be a wonderful enhancement to your backyard oasis. When it comes to selecting the best heating method for your hot tub, each option comes with its own set of pros and cons. Let’s explore the four main heating methods: gas, propane, air source heat pump, and electric, to help you make an informed decision.

  1. Gas Heating: Pros: Gas heaters are known for their rapid heating capability, quickly raising the water temperature in the hot tub. They are suitable for larger hot tubs or when immediate heating is desired. Gas heaters also operate independently of ambient air temperature, making them effective even in colder climates.

Cons: The main drawback of gas heaters is their higher operating cost compared to other heating methods. Additionally, they require a separate gas line, installation, and periodic maintenance, which can add to the overall expenses.

  1. Propane Heating: Pros: Propane heaters share many advantages with gas heaters, offering fast heating and efficiency. They are suitable for locations where natural gas is not available, as propane can be stored in tanks on-site.

Cons: Similar to gas heaters, propane heaters come with higher operating costs and require regular refills of propane tanks, which may become inconvenient and expensive in the long run.

  1. Air Source Heat Pump: Pros: Air source heat pumps are energy-efficient and eco-friendly heating options. They extract heat from the surrounding air and transfer it to the hot tub water, making them cost-effective to operate. They also work well in moderate climates, where air temperatures are consistently above freezing.

Cons: Air source heat pumps might struggle to maintain desired water temperatures in colder climates or during winter months, as their efficiency decreases in low ambient temperatures. They may also take longer to heat the water compared to gas or electric heaters.

  1. Electric Heating: Pros: Electric heaters are easy to install and generally have lower upfront costs compared to gas or propane heaters. They can be an efficient heating option in areas with mild climates or for smaller hot tubs.

Cons: Electric heaters tend to be less energy-efficient and may result in higher operating costs, especially for larger hot tubs or during colder weather. They may also take longer to heat the water compared to gas or propane heaters.

Ultimately, the best heating method for adding a hot tub to your existing swimming pool depends on factors such as your budget, local climate, and preferences regarding heating speed and efficiency. If you value rapid heating and have access to natural gas, a gas heater might be a suitable choice. If energy efficiency and eco-friendliness are essential to you, an air source heat pump could be a great option. Carefully weigh the pros and cons of each method to find the ideal heating solution that aligns with your needs and provides a comfortable and enjoyable hot tub experience.

Do I need a Spa Pack for my Hot Tub?

The answer to this question really depends on how you plan to heat your Hot Tub and also how you plan to control your jets.

A Spa Pack not only contains a heating element (electric) but it also provides the controls for your jets, filter cycles and purge cycles.

The latter two are less important if you are overflowing your hot tub and then using the pool filter, but you still have to think how you are going to control your jets. Also, how are you going to control your heating?

If you want to heat your hot tub separately and you plan to do so on electric, then yes, you do.

If you plan to use another heating method like an Air Source Heat Pump or Propane, then whether you use a Spa Pack comes down how you plan to control your pumps.

You need to be able to switch your pump into a circulation or low speed mode for heating. It is simple enough to wire in a switch to do so. Likewise, for your jets, you can wire in a switch for the high speed.

If it were me, I would use one in conjunction with whatever heating method I was using so I can make use of the thermostat as well as the jet controls. It makes life a lot easier in my opinion.

Yes, it is totally possible to add a Hot Tub or Jacuzzi to your existing pool. Before you embark on the project, you need to have a clear plan of action. You need to understand how you are going to heat it, if you indeed are, as well as how you are going to control your jets.

Case Study – Joe from Michigan, USA, Adding a DIY Hot Tub to his Existing Swimming Pool


Nestled in the heart of Michigan, Joe, a proud owner of an all-season swimming pool, is taking his aquatic sanctuary to the next level. While many Michiganders opt to hibernate indoors during the state’s chilly winters, Joe finds solace and relaxation in the warmth of his pool waters all year round.


Eager to enhance his backyard oasis, Joe had a vision: the addition of a DIY hot tub equipped with rejuvenating jets to complement his swimming pool experience. And so, his journey to create a year-round haven of relaxation began.


Joe actually owns a building company but does not specialize in pools or hot tubs. This means he has the skills for the job.  However, like most DIYers that want to embark on a pool or hot tub project, he recognized that this project was somewhat unique and needed a bit of assistance, particularly in the realms of plumbing and systems design.


To transform his dream into reality, Joe sought my guidance and support to help him navigate the intricacies of marrying these two aquatic worlds – the crystal-clear swimming pool and the effervescent hot tub.


The result? We’re planning on adding a dual bench, square corner hot tub to the corner of the pool that you can see below. The external walls will all remain in situ, and new walls will be created to house the jets. There will also be a trench to house the pipes and keep them under the frost line for those chilly Michigan winters.

How will it turn out? Read on!

Let the story begin for Joe and his DIY Hot Tub addition to what is already a stunning pool!

How the project started – the existing swimming pool.


This is Joe’s existing swimming pool and as you can see too, the awesome dome cover that he uses during the harsh winter months to keep his pool going when most people in Michigan shut theirs down for the winter.

The first thing that needed to be done for Joe was the actual design. I needed to design the Hot tub to fit into his existing swimming pool. However, what joe wanted was to keep the waters totally separate so I was going to design a filtration and heating system as well as a jet system for his new hot tub.

This new Hot tub was going to be located in the corner of his existing swimming pool and he was also going to decide whether to add a Baja deck to the pool or not – we’ll see at the end if he goes with this or not.

Joe and his guys got to work first thing that he needed to do, was actually remove a section of the patio because he needed to relocate the skimmer.

He didn’t want to lose the skimmer as it is an integral part of the existing swimming pool. Dropping the skimmer could have caused problems with the flow, filtration and turn-over of the pool is it was best to just move it.

He just need to move it to the left a couple of feet, so that it wasn’t located in the new hot tub.

With the skimmer relocated, it was time to dig the trench for the new pipework that was going to head over to the new control room for the hot tub.

This trench, as already mentioned needed to be under the frost line of those cold Michigan winters – last thing Joe wants is for those pipes to freeze.

Once the pipes were laid, Joe then turned his attention to forming up the walls, ready to add the plumbing, and then he would obviously fill these with concrete to create a concrete poured structure for his new hot tub inside of his existing swimming pool.

Here you can see the internal seating being formed and you can also see Joe and the team pouring the concrete below is the final result.

Before you pour any concrete into wooden forms, you have to make sure they are really well braced. If not, the sheer weight of the concrete will cause the walls to bow and you will end up with a non-perfect vertical surface.

With any concrete pour, it is important that you leave the walls the right amount of time to cure (dry) properly, before you remove the forms. Doing this prematurely can be catastrophic so be patient on this point.

The next step will be to remove the forms and see how those walls look.


Can I Help You?

If I can help you in any way I would love to hear from you. You can get in touch using the form below.

Thanks - Andi


Hi, Andi here. I own and also write all of the articles and info pages on the site. Some years back now, I built my own hot tub but struggled to find the information I needed. So, once my tub was complete, I started this website to help others in their own pursuit of hot tub and plunge pools DIY building information.

Today, I've helped over 1000 DIY customers just like you all over the world build hot tubs and pools. Have a good look around the site, there are lots of resources here. Please do get in touch if I can help you. - Cheers, Andi

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