Custom Designed Hot Tub: The Design Process, Step by Step

Last updated: September 2026

Building a custom hot tub can feel daunting. The whole reason this website exists is that when I built my own, I just couldn’t find the information I needed. I vowed that when I’d finished, I’d put it all together to help other people. That’s what I’ve done here, and now I help people design their own custom tubs too.

If you’re still deciding whether to go custom at all, start with Custom hot tub: should you build one, and what’s possible?

This is the process most of the case studies on this website have followed. Here’s exactly how it works, what I need from you, and what you get at the end.

First: do you actually need a custom design?

In my online shop there are lots of what I call “off the shelf” designs. There are square and rectangular hot tubs in a range of sizes, infinity hot tubs, swim spas and plunge or cocktail pools. There used to be cylindrical designs too, but they’re not in the shop at the moment.

You might have an idea in your head that isn’t “off the shelf”, though, and want help making it real. That’s where the custom process comes in. Here’s how the options line up:

Option	You start with	You get
Standard hot tub plans ($149)	Choosing a size	CAD drawings, plumbing diagrams, parts list, build guide and video course
Designer Pro plumbing design ($799)	Your design in the free Tub & Pool Designer Pro software	3D plumbing model with PDF images and a video walkthrough, documentation and a parts quotation
Designer Pro architectural CAD and plumbing design ($999)	Your design in the free Tub & Pool Designer Pro software	All of the above plus an architectural CAD drawing in PDF and DWG
Custom hot tub (or pool) design consultancy ($2,497)	A rough sketch and your ideas	The full process below: 3D model, 3D plumbing, CAD, build guide and parts quotation
Custom hot tub and pool combo design consultancy ($2,997)	A rough sketch of both the tub and the pool	The same process, designed for both features together

Prices are as listed in the shop in September 2026. The rest of this post walks through the full custom design consultancy.

Step 1: Order, and send a rough sketch

Every custom tub starts with a rough sketch, and it’s the first thing I need from you. You order the consultancy online, then send me your sketch.

The sketch should show:

• External dimensions and the overall shape.
• The layout you want: seats, loungers, steps and where you’d like to get in.
• Anything fixed around it: walls, the house, a patio, trees or a slope.

It really doesn’t need to be neat. A photo of a pencil sketch on the back of an envelope is fine, as long as the measurements are on it. If you’d like to sketch it in 3D, you can use the free Tub & Pool Designer Pro software instead.

Step 2: Tell me the features

This is the time to tell me about everything you have in mind: how many jets you’re thinking of, waterfalls or water blades, lighting, benching, an infinity or overflow edge, a swim jet. If there’s anything else that’s pertinent to the design, now’s the time to mention it.

It matters because every feature changes the plumbing. A water feature needs its own pump and a lower drain, for example. More than about 16 jets needs a second jet pump. These need to be designed in from the start. See How many pumps do you need? and Adding a water feature to your DIY hot tub.

Step 3: Confirm the control room and build method

If you’ve read around this website or watched my YouTube channel, you’ll know the control room is key. I need to know:

• Whether it’s above or below the water line. That decides whether you need self-priming pumps.
• How far it is from the tub. Distance and pipe runs set the head the pumps work against, which decides the pump size.
• How you’re building the tub: block, ICF, poured concrete or something else.

I’ve written about this in depth in Hot tub control room position and Hot tub control room design considerations. If you’re still choosing a build method, see Hot tub wall construction: what are the options?

Step 4: Send photos and a video walkthrough of the site

Along with the sketch, send me photos and a short video of where the tub is going. Walk around the space, show me the access, the slopes and where the control room will go. It gives me a real feel for how the tub should look and fit into the space, and it helps me spot potential problems early, such as drainage, access, level changes or anything structural.

Step 5: The 3D model

This is where your ideas come alive. I build a full 3D model of the tub, and it’s an interactive process. You’ll get lots of emails or WhatsApps from me with screen grabs of the design, and we go back and forth as many times as needed until you’re happy. Nothing gets finalised until you are.

Once you’ve signed off the 3D model, it’s time for the plumbing.

Step 6: The 3D plumbing layout

The plumbing is less of an interactive process, because most of it is set by rules and precedent: drains, skimmer, pump, filter, heater, jets and the blower lines, all in the right order and the right pipe sizes. If you want to understand the principles, have a read of DIY hot tub plumbing.

What the 3D plumbing layout gives you is a way to see exactly what goes where within the design: every pipe run, jet and component. Understanding how your tub works is really important, and this is the best way I know to do it.

Step 7: The architectural CAD drawing

With the 3D model and plumbing done, the design goes to the CAD and structural engineering team, who produce the dimensioned architectural drawing.

If you’re using a general building contractor, this is the drawing they’ll want. They don’t want to trawl through a 6,000-word document. They want a single drawing that shows them what to build. It’s also what you’ll usually need for a permit application. If you’re using contractors, have a read of How to avoid mistakes when using contractors to build your hot tub and Do I need a permit for my hot tub?

Step 8: The build documentation

Next comes the documentation for your project: a 6,000+ word build guide covering everything from sealing concrete to insulation, water chemistry and installing the equipment.

I’ve built this document up over the years, and it delves into the depths of all things DIY hot tub. If it’s not in there, it’s probably not needed. Bold statement? Perhaps, but it’s tried and tested, and it’s been used to build literally hundreds of tubs. If you find something missing, let me know and I’ll add it. Having the best documentation matters to me.

Step 9: The parts quotation

Finally, you get a parts quotation specifying everything the design needs: pumps, heater, jets, controls and plumbing fittings. Because it’s built around your 3D plumbing layout, you know the parts fit together and match the design.

The process in a nutshell

1. Order, and send a rough sketch with external dimensions.
2. Describe the features you want (jets, waterfalls, benching and so on).
3. Confirm the control room position and build method.
4. Send photos and a video walkthrough of the site.
5. 3D model, refined together until you’re happy.
6. 3D plumbing layout added to the model.
7. Architectural CAD drawing.
8. Build documentation.
9. Parts quotation.

Communication is mainly by email, with WhatsApp for sharing screenshots of the 3D model and quick back-and-forth on design decisions. The typical timescale from order to final delivery is 2–3 weeks, depending on how many revision cycles we go through.

How the Designer Pro route differs

If you’ve already designed your tub in the free Tub & Pool Designer Pro software, you can skip the sketch and 3D modelling stages. You order the architectural CAD and plumbing design using the email address on your Designer Pro account, we talk through how and where you’re building it, and then you receive the 3D plumbing layout, the architectural CAD (PDF and DWG), the documentation and the parts quotation. If you don’t need the CAD, the plumbing design on its own is the lighter option.

How to get the most from the process

• Measure the space properly, including anything that limits it: boundaries, drains, manholes and overhead cables.
• Decide the build method first, or tell me you’d like advice on it.
• List every feature up front, even the “maybe later” ones. It’s far easier to leave a sleeved pipe for a future water feature than to cut into finished concrete.
• Think about the control room early, and make it bigger than you think. I didn’t, and I’ve had to rebuild mine since.
• Know your heating plan: spa pack electric, gas or propane, or an air source heat pump. It affects the plumbing and the power supply. See What is the best method to heat my DIY hot tub?
• Check your permissions before you pay a builder, and allow for a qualified electrician for the supply.

Common mistakes

• Changing the shape after the plumbing is designed. Every change to the shell means rechecking the plumbing.
• Treating the 3D model as a nice picture. Sign it off only when you’d be happy to build it exactly like that.
• Skipping the site video. It’s the quickest way to catch problems with access, levels and drainage.
• Buying parts before the design is finished. Wait for the parts quotation so everything matches.

Ready to get your custom tub designed?

If you’ve got an idea you’d like to make real, the custom hot tub (or pool) design consultancy takes you through every step above. If your project includes a pool as well, choose the hot tub and pool combo design consultancy. If you’d rather design the shape yourself, start with the free Tub & Pool Designer Pro software and add the architectural CAD and plumbing design. And if a standard size fits, my DIY hot tub plans are the simplest place to start.

FAQs

How long does a custom hot tub design take?

For the custom design consultancy, the typical timescale from order to final delivery is 2–3 weeks. It depends mostly on how many rounds of changes we make to the 3D model.

What do I need to provide to start a custom design?

A rough sketch with external dimensions, a list of the features you want, the control room position and build method, and photos and a video walkthrough of the site.

Can I change the design after I see the 3D model?

Yes. That’s what the 3D stage is for. We go back and forth until you’re happy before anything is finalised.

Will the CAD drawing work for a permit?

The architectural CAD is a dimensioned drawing made for contractors and permit applications. Requirements vary by area, so check with your local building department, which may also want an engineer’s stamp.

Do you build the hot tub for me?

No. The consultancy is the design, documentation and parts quotation. You build it yourself or give the drawings to a builder.

What’s the difference between the design consultancy and the plumbing consultancy?

The design consultancy covers the whole tub, from the shape to the CAD. The plumbing consultancy is for when the structure already exists (or is already designed) and you only need the 3D plumbing schematic, parts specification and email support through the build.

Got a question about the process? Ask it in the comments below. I read them all.

Cheers,
Andi

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Thanks - Andi

 

Hi, Andi here. I own Buildahottub.com 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.

Fast forward to 2025, I've helped over 1400+ 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