DIY Hot Tub Designs

hot tub in wooden deck with stone and grass landscaping
  • 3-100 hours
  • Intermediate
  • 300-2,000

Soaking in a warm tub at the end of the day is a blessing we often don’t find the time to embrace. It’s a luxury that helps us relax and transition into whatever comes next.

A hot tub adds the benefit of immersing us in the outdoors. However, a commercial hot tub is an expensive investment. If that’s an investment you’re unwilling or unable to make, consider creating your own version of a hot tub for you and your family to enjoy.

There are many ways to tackle this DIY hot tub project. Start by making some preliminary decisions and use these designs as a guide in creating your own custom model.

Size and Shape

The first consideration is how big you need your hot tub to be. You can create a space for one or two people or scale that up for the entire family. The size and shape of your ideal hot tub are guiding principles for the finished product.

Think about whether you’ll want an oval shape that comfortably seats one person on each end or if you’re more inclined to go with a larger and more traditional square outline. There are many styles of round options too.

hot tub with wine glass and triangular corner

Materials

The idea to create your own hot tub may have spawned from materials you have around the house. For example, if the stock tank is no longer being used for livestock, you could convert it into a hot tub for yourself.

The same goes for wood planks and other materials. You can even use a broken chest freezer, a bathtub you’ve replaced during a remodel, or other types of tubs and tanks made to hold liquids.

Don’t worry about whether your material choice is pretty. If it’s not, you can always build a surround for aesthetics.

Location

You probably have a location in mind for your DIY hot tub. Commonly it’s on a patio or in the backyard. You can also place a hot tub inside the house if you have the space to accommodate it.

The location may influence the size and shape of your hot tub. If you’re wedging it into a narrow walkway, for example, you’ll be looking at a long oval design.

For a square hot tub, you’ll need to consider how much of your patio you want to take up. Using an existing patio is a good plan, however, since it keeps you from having to do a lot of the prep work before installation.

Although hot tubs are self-contained rather than being connected to the home’s plumbing, you will want to consider a water source for filling the tub. Although it might be nice to place it on the edge of the yard, make sure you’ll have a way to fill it once you place it.

Also think about how far you will realistically want to go in order to enjoy your hot tub. In mild climates it might not matter, but if you live somewhere cold, a trek across the yard may be unpleasant in a swimsuit.

hot tub on deck in snow

Electrical Access

If you plan to tap into the home’s electricity, you’ll need to place your hot tub close enough to access the existing wiring. This can also influence your location decision.

Heating Sources

There are many ways to heat a hot tub. One popular trend uses fire to warm the water inside the pipes. This requires consistently monitoring the fire as well as keeping a supply of firewood available for this purpose.

Wood fire is also difficult to regulate, so you may find your water taking too long to heat up or easily overheating, requiring time to cool back down before use.

You can also rely on propane gas. It’s convenient and highly efficient. It’s also easier to regulate. However, you will have to monitor your usage and refill the propane as needed.

A heat pump is another option, as is wiring the system into your home’s electrical panel. For a green, off-grid option, hook your hot tub up to a solar panel as your energy source.

Costs

Building your own hot tub should cost substantially less than buying a new model. However, it might cost more than you think.

After you’ve mapped out your dream tub, run the numbers. Remember to include piping, which might just be some PVC or copper. A note here, always use copper instead of galvanized steel if you will be applying direct heat, such as fire. You may also be adding jets, a pump, filter, and decking.

The primary vessel you use might be the biggest cost. The prices of stock tanks went through the roof during the pandemic due to the cowboy pool craze, so if you haven’t checked prices in a while, hit up the internet. However, if you’re using an old freezer as your vessel, the costs will be significantly less.

Also factor in any special tools, such as hole saw or other attachment for creating the pipe openings.

DIY Hot Tub Designs

Alright, with the groundwork out of the way, let’s get into a few design examples.

stock tank hot tub

Stock Tank Hot Tub

Perhaps one of the quickest and easiest hot tubs comes from a basic stock tank. You can choose any size or shape to work with.

Step 1 - Prep and Place

You can place your stock tank anywhere it works for you. An existing patio works, as does an elevated platform or even on the ground. If you build a platform, ensure it can handle the weight of the filled hot tub, including body weight.

Even if you plan to place it on the ground, keep it from sinking in by placing concrete supports underground. Make sure they are level. Then cover them with some soil and sand before placing the stock tank.

Step 2 - Drill Holes

Drill one hole near the bottom of the stock tank on one side. Make the hole the same size as the piping you’ll be using (around 1 ⅜”). Then drill another hole about 18” above that opening.

Step 3 - Install Tank Fittings

These are the units that will hold the hoses and allow the water to filter throughout the tub. One draws water out to the heater while the other pours heated water back into the tub.

Install the inside and outside components through the holes. Then seal them with silicone caulking to hold them in place and prevent leaks. Add the appropriate attachment for your copper tubing to the outside of the tub.

Hint: If your copper tubing isn’t a good fit for your fitting, use a section of garden hose to attach the two, securing each end with hose clamps.

Step 4 - Form Copper Tubing

Create a spiral shape out of the copper tubing. A straight piece will go into the bottom tank fitting. The copper will then twist around and around, rising up to where the other end of the copper fits into the upper fitting.

Separate the layers of the spiral as it goes up with a stake on each side. Support the copper by inserting nails into the vertical stakes at each level. Be sure to use a metal that can handle the heat of fire.

Another option is to use an old washing machine basin. Place the coiled copper inside the basin with the ends stretching back to the bathtub.

Step 5 - Build a Fire

With all your components in place, build a fire underneath the copper coil or in the basin. Make sure your tub is full of water before beginning.

Warm water is lighter than cold water, so it will automatically create a suction as the water in the tubing is heated, cycling the warm water out the top and drawing more in through the bottom in continuous motion.

Note: This same method works for a bathtub, old freezer, or other vessel.

An additional note about fire: You can make this project as simple or advanced as you like when it comes to fire. The open copper will heat with a fire placed directly below it. However, for a long-term and more stable solution, enclose the fire area or attach the hot tub to a wood-burning stove.

Round Cedar Hot Tub

round cedar hot tub spa

Another popular type of hot tub is made almost completely from wood, specifically cedar. Building cedar hot tubs requires more work, resources, skills, and tools than the first example. It’s not a project for someone with limited woodworking experience. This is an advanced project.

Step 1 - Source Your Cedar

You can buy the cedar planks or plane them yourselves if you have the means. The number of boards will depend on the overall size of your hot tub and whether you’ll be adding benches or other accessories.

Step 2 - Cut Boards

The key to piecing together a waterproof cedar hot tub is cutting each board to fit together in a tongue and groove fashion. All boards across the bottom and up the sizes will slide into each other. All cuts need to be precise to eliminate leaks.

Step 3 - Build the Floor

Layout your prepared tongue and groove boards. Drive them together and reinforce them from the bottom with cross supports. Use a long thin board anchored to the middle of your base that can pivot in a circular motion.

Place a pencil on the outer edge and move around your boards to outline the shape of the hot tub floor. Then cut the circular shape and sand down all the surfaces. Add a foam strip around the edge of the floor.

Step 4 - Add the Vertical Staves

In addition to having tongue and groove edges, the vertical staves need to have a wedge cut out where they will slide over the foam edge of the flooring. This helps create a tighter seal. The wedge needs to be precise.

Tap each stave into place, ensuring a tight fit both into the floor of the hot tub and into the staves on each side.

Step 5 - Add Support Bands

Choose a strapping system to hold your boards in place. Install one band near the top and another closer to the bottom, plus one around the middle. Look for any significant gaps between boards, and make adjustments as needed.

Step 6 - Seal the Wood

Add a sealer to protect your hot tub from sun damage. This may take a few coats, potentially applied several days or even one week apart.

Step 7 - Build Steps and Benches

This is an advanced project with many steps. You’ll need to design and build steps for entering the tub. Since it’s deep, you’ll also want seating so you don’t have to squat in your hot tub while relaxing.

Step 8 - Add Plumbing and Heating

Finally, drill the required holes and connect them to whatever heat source you choose. Also include the pump and filter systems.

A Note About Jets

hot tub jets

Many DIY hot tubs are just that--a tub that gets hot. However, you can add your own jets as well. To place jets, run PVC pipe through the walls of the vessel at the desired height. Attach the jet housing to the pipe in each hole. Then attach the actual jets.

In Conclusion

These two examples should give you an introduction to the process of building your own hot tub and show the vast array of options in doing so.

You’ll have many decisions to make about the size, shape, material makeup and layout of your hot tub. In addition to the wood or prefabbed options we’ve outlined, you can pour a concrete hot tub or build one from securely attached blocks or bricks. In reality you can dig a hole and line it with a tarp.

The point is, you can make a hot tub out of anything that holds water and anything that heats it. The question then becomes your ideal for each.

Be realistic about your skills so you don’t get into hot water with this project (pun intended). For example, get some help if you need to drill through concrete or fiberglass and aren’t comfortable with that.

Similarly, you may need to borrow or purchase more tools in order to have the right tool for the job, such as when doing joinery work.

Building your own hot tub should be a fun and gratifying experience. After all, what can be more rewarding than soaking in a hot tub at the end of your project.

If you’re still considering all your options, read about Inflatable Hot Tub Pros and Cons and Cedar Hot Tub Pros and Cons.