Planning is key. If the planning stage is done correctly, it will make the rest of the build much easier.
I learnt the hard way by not planning to have enough space for my “control room” as I call it which is where your pump and electronics go; we’ll look at this later in this website.
There are quite a few things to consider so in this a chapter, we’ll take a look at the variables.
So where are you going to put your Hot Tub? You may not have the luxury of multiple potential locations in your garden, but if you do, here are a few things to think about. How are you going to fill it? Yes, your Hot Tub is going to need water and it is going to need topping up every month or so depending on the use so you need to have a water source eg tap nearby. Yes you can run a hose, but it doesn’t look as good as getting the plumbing right for being able to fill the tub.
How are you going to empty it? You are going to need to do this a couple of times a year minimum to make sure your water is nice, clean and healthy. How are going to empty your tub?
With the volume of water and chemicals, you are not going to be watering your flowers with this water!
Where is the drain and how are you going to get there? For this one, you can run a hose when you need to empty it and we’ll discuss this when we look at plumbing.
What do you want to look at when you are in the tub? Is there a view? Perhaps this may seem an odd point, but if you do have the option of a view, you really want to take it as opposed to looking at a wall! This can also potentially affect where you place the plumbing and jets. These are also not options that you would get with a shop bought tub. You get to customise this to your exact requirements.
Where are you going to locate your “control room”? Pumps, pipes, blowers, all take space and need to have it allocated and allowed for.
You are going to need electricity to your tub one way or another and we will look at this later in the book in a chapter dedicated to electricity. Where is it going to plug in?
What landscaping are you planning. Do you need space for a deck around your Hot Tub or space for steps. Lots of things to think about on the location but most of these will depend on where you are planning to install your tub.
For me, I needed to clear away some space. This is what it looked like before I cleared the area.
As you can see, the area was somewhat wasted. A parking lot for the kids toys and a Goosbery bush that I was not fond of anyway. After a few hours on a Sunday afternoon, it was looking more like space for a Hot Tub.
You can see in the above picture that I was very much still planning at this stage. Trying to work out sizes and what the actual dimensions of the Hot Tub were going to be. At one stage I even had the wife and kids sitting in the dirt pretending to be in the tub so I could try and gauge the size of it.
Above ground or in ground?
This is a crucial question as it will affect the design of your tub. Personally, I chose in ground as I wanted it to be as minimal as possible in my garden. I also liked the idea of dropping into the ground rather than “being on display” for all the neighbours to see. I also was a little nervous about the brickwork and how well I was actually going to lay blocks as I had not done it before. There is quite a bit of water volume in the tub, 2800 litres in my case which is nearly 3 tonnes of weight. By opting for an in ground tub, I knew that I could back fill the brick work with concrete so this was going to minimise the potential for a wall to split and flood my garden!
External Roof or Indoors?
Are you planning on building a roof over your Hot Tub or even a full building? This is the time for making all these decisions and plans as the later you leave it, the harder changes. Things like positional footings would have to be considered at this stage, not something you want to be adding afterwards.
Physical Dimensions & Design
For me, this was the biggest consideration. Whilst I had the space for a larger Hot Tub, there were a few things I hadn’t considered. My initial design was about 50cm/20″ larger in each direction. You can see the dimensions at the end of this guide, but what I hadn’t considered was heating and filtering. My Hot Tub is a good size, comfortably being able to seat 10 adults. I wanted something where the kids could play in it without climbing all over my wife and I – there was a method in my madness! That said, what I hadn’t considered was the heating.
With the dimensions that I had, taking me to over 4000 litres of water, I was verging on a small swimming pool. Once you hit swimming pool size, you start to enter into what I affectionately began to call “Swimming Pool Tax”. “Swimming Pool Tax” is not something that the government or local authorities are going to collect from you, it is what I affectionately called the additional cost of any components that are swimming pool size or compatible.
For example, if hot tub component “X” is fifty quid (50 USD), the swimming pool equivalent of component “X” is seventy five quid (75USD)- the difference being my “Swimming Pool Tax” This was the case on things like filters, lights, drains, skimmers, all these things that by increasing the size I needed to move into the “Swimming Pool Tax” territory.
The biggest point here about the size was the heating. Whilst at this stage I had not considered the running costs (we’ll look at those later too) it was the practical nature of heating the tub up to temperature. You want to be running your tub at somewhere between 37 and 40 degrees (98-104F). To get 4000 litres of water to that temperature and to maintain it was going to be a challenge!
When I spoke to my Spa & Hot Tub Component supplier John who is very knowledgeable and was extremely helpful throughout the build, he was suggesting I needed a custom built heating element that was 12Kw. This is 4x the heater that I have in my tub now and 4x the heaters of most tubs! This was before I got to the cost to purchase and to run (about £1.70 ($1.70) an hour!) that was just mind boggling! Needless to say, I stayed away from that.
I dropped the dimensions down, added larger internal steps and seats to decrease the overall volume of water and brought it back to a level where I could use an “off the shelf” Spa Pack – this is the heater and electronics to control the pumps and blower etc. So when you are designing your layout, you need to mindful of not just the dimensions but the volume of water. This will also dictate what filter you need and what pump you will need and what your ongoing running costs are going to be.
What are you going to build your hot tub out of. I am sure you have already had a look around YouTube where you can find some interesting videos for tubs made of wooden barrels and various other recycled materials. I’m also sure you have seen the “shotcrete” or “gunite” swimming pools and spas being made.
These are really cool to watch and they involve the pool or spa to be formed with a metal rebar structure. The piping and plumbing is then attached in place to the rebar and the whole thing is filled with concrete that is sprayed in at high pressure then skimmed flat. For us DIYers, this is not an option. Very cool, but requires a lot of skill that even those of us who think we can do anything (me!) should stay away from.
There is a simpler option. I opted for blocks, concrete and mortar and would highly recommend this method. As a newbie to brick laying, firstly it works, I’m testament to this and it wasn’t overly difficult. The other thing I was able to do with this method was use lots and lots of concrete. Being a first time brick layer, I wanted to make sure that the structure I was creating was going to withstand the pressure. Being able to backfill behind the blocks (if you remember I opted for in ground construction) gave me total peace of mind that I was going to create a very strong structure.
The other thing you need to think about is what finish you are going for. It is totally possible (and cheaper) to skim the tub over with a waterproof concrete render, and then paint it with a waterproof paint. Are you considering the swimming pool approach with the small tiles. Fiddly, but they do look nice. Or, are you considering something like the finish I went for which was waterproof floor or wall tiles. I also went for quite large tiles to minimise the about of joints and grouting needed. You don’t actually need specialist tiles as long as they are waterproof and suitable for walls and floors, you should be able to use them.
In regards to materials, at every stage ask yourself how is this adding to the waterproofing of the tub. Every element needs to be adding to this. You should be adding water proofing agent to your mortar for laying bricks, waterproofing agent into your render, some form of sealant over your render (I used PVA) and then if you are using tiles (which we have already established should be waterproof themselves) both the grout and adhesive need to be swimming pool grade which is waterproof too.
What shape are you going to opt for? Remember, this website is concentrating on building using concrete blocks, they are square. Most of your shop bought tubs are cylindrical. It is certainly easier to make a square tub using cinder blocks, but they are quite easy to cut with the right saw (15 quid ($15 USD) off Amazon) so you could create a hexagonal or a more ambitious shape if you wish. Do remember that you are potentially going to be tiling this too so the more ambitious the shape, the more difficult the tiling is going to be. Food for thought.
Plumbing, Lighting and Audio Visual
At this stage, eg the design stage, you need to be thinking about where your jets are going to go. Are you putting in any underwater lighting (yes you should as it looks really cool) and any other Audio Visual components you are thinking of having. For example, do you want speakers and some form of Bluetooth system for sending audio from your phone?
We do have a full chapter on plumbing, but one of the things I would like you to think about at this stage is where is the skimmer going to go (This is the top filtering element where bits of debris from the surface drop into a basket so can be removed) and also where are the two bottom drains going to go. You need two so if one does get blocked, it is not going to ruin your pump. Incorporate these into your design now rather than later. Certainly, this should be done before you break ground.