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.


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

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.

In Conclusion

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.

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 700 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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