Adding a Hot Tub to a Pool – Case Study – Scott, AZ, USA

Add Hot Tub To Pool

Scott from Arizona, USA first got in touch with me back in May of 2022. He was looking to add a hot tub to his pool. Having put the feelers out to see how much it would cost to get a builder to do it – Scott decided that it was something that he felt with my advice and guidance, he could do himself. It was going to be a fun project for him and his son but most importantly, he would save a whole bunch of money in the process.

Fast forward to January 2023 and Scott was almost ready to start. He hired me to design a custom layout for his hot tub so that it could make use of the pool kit from his existing swimming pool in terms of heating and filtration but also, it would have separately controlled jets.

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Here is what Scott is going to be building and hopefully over the forthcoming weeks and months you will be able to see this take shape.

Scotts Hot Tub
Scott’s Hot Tub

What Scott is excellent at is planning. He plans everything to the absolute Nth degree and this is really helpful when you are taking on a project like this.

Scott also likes to fully understand everything in complete detail before he will undertake it. Again, a highly advantageous trait of one’s personality when you are going to embark on a project like this.

The first step for Scott was to mark out the area for the tub and then he was going to try it all for size. Again, planning, planning and more planning.

Adding a hot tub to pool

Let the Hard Work Begin.

As time stops for no-one, we’re now into the summer months in Arizona. As I am sure you can imagine, it is hot and very hot. What better way to spend ones summer vacation than to get roped in by your dad to dig a hole for a new hot tub.

It was back breaking work, but Robbie got stuck in.

diggin a hole

However, you really have to take into account here just how dry and hard the ground was. Not being a total slave driver (lol) Scott did get some very welcomed help for Robbie in the form of a digger. That made his life a lot easier!

When you are digging the hole, you need to remember not only have you got the +/- 43″ of depth that will be the hot tub, but you also need a further 6-10″ for the base – that is a deep hole and a difficult dig to do that by hand.


Trying it for Size

As you would expect with Scott, he wasn’t just going to go ahead blindly into putting the block in place, he wanted to try them (dry) for size. So that was the next step for him, he created the shape he was going to build out of the blocks so that he could try it for size. Again, planning planning and more planning – fantastic.

try it for size

Time for a Vacation

At this point it was time for Scott and family to head off on their summer vacation. Now, you would expect some good and old fashioned R&R but not for Scott, he was still thinking and planning his tub.

This was helped with one of the pools getting refurbed where he was staying so this was fuelling his curiosity – and of course, he took his planning document for some “holiday reading” that I had written for him durning the design phase.

He was even emailing me questions from the sun lounger – that is keen Scott!

The Practice Run

Back from vacation, the next step for Scott and Robbie was to turn their attention to the existing pool pad. We are going to modify the plumbing, “hijack” on the of the existing pool returns to send that to the hot tub to create an overflow.

This was also an opportunity for them to practice their concrete work as they needed to pour a larger pad. Nice work Gents!


As this practise went well, the next step for the guys is to actually pour the base of the tub. “No going back now” was was the email I got from Scott at this point – well, he could just pour all that rubble back in the hole I guess, but I am sure Robbie would have something to say about that!

All hands on deck, time ti mix some concrete.

mix concrete

Before you pour a base, it is always a good idea to use a liner to keep dirty water ingress out of the tub. Some people don’t bother, I tend to though (much to the dislike of one troll on YouTube who claimed I was single handedly destroying the planet with singe use plastics – er, go and have a chat with Greta….) For the record I do recycle 😉

If you are having some swimming pool style drains in there, (the flat ones at the bottom, great for circulation not for jets as the flow rate is too low) this is the time you need to get them in place too.

Nice work Gentlemen, this is coming along really nicely.

base in place

Pad Done, Time for Some Walls

Would you believe it, we are now in December 2023. Whilst most of the Northern Hemisphere has stopped building as it is too cold – Scott on Robbie and the wonderful Arizonian climate are cracking on with their build. 

With the pad in place, it is now time for some walls. Scott is using the hollow 8″ CMU blocks to which he will add rebar and then fill with concrete after the plumbing is in place.

They are cheap but also very strong so apart from having to core holes in them to get the plumbing in place, which isnt too big of a deal, they are a great material to work with.

And here we have it – the current state of play on December 13th 2023

The lower 2.5 courses of block are in for the footwell. Next steps will be the seat’s concrete pour followed by the retaining exterior walls.

Time for some pipework


The next steps for Scott were to start on the plumbing. This was not going to be straight forward as there are several things that we have planned to change.


Firstly, we need some new pipe runs for the hot tub jets.


Secondly, we need some pipe runs for the hot tub circulation pump – so that we can heat and filter the water separately.


Lastly, we needed some runs for the waterfall. Basically, we are hijacking one of the existing pool returns so that we can delivery pool water into the hot tub. This means that we are putting more water in that it can hold so that it will overflow and give us a waterfall.


This is on a diverter valve so that it can be turned off when it comes to the heating. The last thing that you want to do is deliver cold pool water to a hot tub that you are trying to heat – totally counterproductive.





Scott also needed to get some jets into the tub at this stage. This involved coring some holes into the walls and then cementing the pipes back in place so that they are watertight. It is an involved process for sure.


Render and Waterproofing


With the jets in place, it was time to render the walls and then apply the waterproofing layer. To render the walls, Scott used a waterproof render mix. All this is a a regular render with some additive that reduces the amount of air in the mix. This is done as as the blocks themselves are porous, so they do need to be sealed.


With the render on, then you can waterproof the surface. There is no shortage of different brands of waterproofing material – Ardex, Latticrete Mapfei just to name a few. All the products that are “pool products” will be just fine.


Water Testing


Scott’s big worry is that his tub is going to leak. I’ll be honest, this is the biggest worry of most DIYers. The challenge that we face is that it is very difficult to pressure test a set of pipework as a DIYer. It involves an awful lot of kit that most of us just don’t have lying around in the garage.


You also must cap off the 2.5” Gunite pipes to do this too.


What is the alternative? Well, you can do a water test. In short, fill the tub, close off the plumbing and see if you have any evident leaks. You are looking for a drop in water level overnight and you can visually inspect the pipework and the tub for leaks.


I know this is not the same as water being under pressure, as when Scott connects the pumps the water will be under pressure so he might still have some leaks. This is not something that is easily tested for in advance.


I always say on the plumbing, if you have doubts that you have made the joint correctly, or you have forced it into the fitting, then it is going to leak. Cut it out and do it again – there are no short cuts when it comes to making a good plumbing joint and well-made plumbing joints don’t leak.


Scott did find that the seal around one of the jets was leaking but that was all he found which was a relief.


Next Step – Control Room Remodel


With the addition of the hot tub to the pool, there was of course going to be some additions to the pool pad / control room. We needed to have a new filtration and heating system just for the hot tub. There was the new jet pump (all pumps self-priming as the pad is above the water line) and there is a spa pack in there too. This took care of the new parts – what about the remodel.


Well, we needed to change the pool plumbing so that we can divert on of the pool returns that we have hijacked to enable the overflow waterfall effect.


This all sounds more complicated than it actually is – Scott is of course following the plan that I drew up for him.


What comes next? Electrics


With all the addition of the new kit, there are some modifications to the electrics that are needed. I must add here that all modifications to electrics should be done by a qualified electrician.


Adding a new heater, 2 new pumps and some new lighting was going to increase the current draw on the main pool breaker box by about 60A. We needed to make sure that there was enough “juice” available for all this kit as previously the other pool kit was on much lower breakers.


A qualified electrician will also be able to advise on cable thicknesses as you can’t just stuck 60A though a cable that is designed to take 15A for example – it would get hot and potentially melt.


Check back soon for an update on Scott’s build.



DIY Hot Tub Build Project Update: Scott in Arizona Makes Progress on His Hot Tub Addition

We’ve seen how Scott had run the pipes from his control room to the new hot tub location and insulated them to prevent freezing during the cold Arizona winters. He had also finished plumbing around the tub itself, installed the jets, and rendered the surface of the tub with waterproofing.

This is the next series of updates from Scott.

Leak Test and Plumbing Check

Since pressure testing a DIY hot tub  is complicated and requires specialized equipment, Scott opted for a simpler leak test by filling the tub with water.

He plugged the plumbing and checked for leaks. This method is a good way to identify leaks in the structure of the tub and any glaring plumbing errors that need fixing before he proceeds.

Fortunately, the leak test only revealed a minor leak around one of the jets, which Scott was able to seal.

Revamping the Control Room for the Hot Tub Addition

To accommodate the new hot tub, Scott is modifying his existing pool control room plumbing. He is repurposing one of the existing returns to create an overflow from the hot tub into the pool.

Additionally, new plumbing is being installed for the hot tub, allowing for separate heating, filtration, and circulation.

Scott is using self-priming pumps because the control room sits above the water line. A powerful 3-horsepower Black & Decker pump and a Hayward circulation pump are being installed. The filter and electrical components, including the Spa pack, are also being placed in situ.

Electrical Work Needed for the New Pumps and Heater

The addition of two new pumps and a heater necessitates electrical work. Scott will need to reroute some cables and increase the circuit amperage to accommodate the additional electrical load.

Electrical work involving changing breakers or increasing circuit amps should always be performed by a professional to ensure safety and prevent electrical hazards like melted cables, tripped breakers, or even fires.

Stay Tuned for More Updates

Scott will soon be working on the electrical aspects of the project with a qualified electrician. Check back soon for an update on his progress.

Time for Some Hot Tub Electrics

Normally, plumbing is the trickier part of a DIY hot tub build, but in Scott’s case it was the electrics. The biggest challenge was figuring out the wiring for the new Spa pack.

Spa packs use a 230 volt feed, and Scott had trouble understanding the pin configurations for the amp cables. This is because unlike regular domestic electrics, hot tub electrics use different voltages on different pins which can be hard to get your head around the first time you do it.

I have the same conversations with electricians doing hot tub installs that I do with regular DIYers so Scott was in good company!

Another challenge Scott faced was programming the Spa pack. The Spa pack needs to be programmed to recognize what equipment is connected to it, otherwise it won’t function properly. For example, if the air blower isn’t programmed correctly, it won’t turn on.

It can be incredibly frustrating when things don’t work and Scott over these last couple of weeks has certainly had his share of frustrations.

Eventually, with my assistance, Scott was able to get everything working – check out the video above to see Scott “checking” that his tub is working.

Next steps, hot tub interior.

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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