Doug’s DIY Infinity Hot Tub with Swim Jet in Virginia (Case Study)

Last updated: September 2026

Ever dreamt of soaking in a hot tub with an infinity edge that blends into the view? Doug from Virginia is making that a reality by building his own custom infinity hot tub, complete with a built-in swim jet.

Like many of my customers, Doug got in touch because he knew what he wanted to build but wasn’t 100% sure how to do it. He also didn’t want to pay the crazy prices pool builders charge for this kind of work. So Doug hired me to create a custom design for him, and once it was done, I supplied all the parts for the hot tub too.

This case study follows his progress from the first dig onwards, and it’s documented on my Buildahottub YouTube channel too.

The design

The centrepiece of Doug’s build is the infinity edge. It creates the illusion of water flowing effortlessly over the edge, and it makes a stunning focal point.

To get that effect, there’s a hidden balance tank. It acts as a reservoir, taking the water displaced as people get into the tub and giving it back when they get out, so the edge keeps flowing. I explain how to size one in how to build a DIY infinity or overflow hot tub.

Planning the plumbing

An infinity hot tub needs careful planning, especially the water circulation. The plumbing that moves water between the balance tank and the hot tub has to be designed in from the very beginning. Retrofitting it later is hard work, so getting it right at the design stage is crucial. For the swim jet side of things, see swim jet considerations.

Excavation

Doug started with the groundwork: excavation. As with most DIY pool or hot tub builds, digging a big hole is the necessary first step, and the video shows a lot of soil coming out.

But what about all that dirt? Doug had to arrange a truck to haul away the excavated material. It’s a practical detail to plan for on a project like this.

With the groundwork done, the next stage was pouring the concrete base. You can also see where Doug has placed the rebar in the excavation for reinforcement. Watching someone dig a hole might not be the most action-packed part of a project, but things were about to get much more exciting.

Pouring the base

This is where it starts to get interesting. Doug was no longer just digging holes. With the concrete pour, his hot tub started to come to life.

With all the rebar in place, it was time to pour the base. Rather than mixing by hand, Doug had the concrete delivered. Good call, Doug! That was a whopping 15 cubic yards of concrete.

When you order concrete, ask for 4,000 PSI strength. If possible, you can add fibres and a waterproofing admixture, although these vary from supplier to supplier. What you don’t want in the mix is air. Air in your concrete leads to bubbles, holes and potentially leaks, so avoid it. My concrete slab and base guide covers the details.

The challenge for Doug was that all this concrete had to be moved by wheelbarrow, not pumped in. When you have a delivery like this, rope in as many friends with wheelbarrows as you can. You pay for the concrete, but there’s also usually a charge for waiting time. If it takes you several hours to unload, you’ll be racking up a bill.

Doug started by pouring the base for the balance tank. With that in place, he moved on to the rest of the tub. When you pour your base, all the plumbing, like the main drains, has to be in place first. It’s very difficult to add them afterwards. See installing a main drain.

The concrete should come right up to the lip of the main drains. They need to end up flush with the surface so the grille sits nicely on top when you’re done.

With the base poured, it was a waiting game while the concrete cured. The next stages were putting up the forms for the walls, adding the plumbing and pouring the walls.

All systems go for Doug, and it’s coming along really nicely. Nice work, and thanks for the pics as always!

Forming up and bracing the walls

With the rebar structure in place, the next step was putting the forms up. Forms are basically large moulds that the concrete is poured into to “form” the walls.

The thing to remember with forms is that they need to be braced, and braced well. If you don’t brace them, you’ll end up with curved walls, and that’s the last thing you want. Concrete weighs a lot, and the OSB or chipboard usually used for forms (because it’s cheap) isn’t strong enough on its own.

As you can see from Doug’s photos, he’s gone to town on the bracing. Better safe than sorry.

Bonding

Another essential part of this stage is bonding. Bonding connects all the metal in and around the water, including the rebar, so it’s all at the same voltage. If a fault or stray voltage does appear, there’s no difference in voltage between the things you can touch, which reduces the risk of electric shock. In the USA it’s required by the NEC. I’ve covered it in full in ground bonding a hot tub or plunge pool.

Then it was time to put in the plumbing and brace up the forms ready to pour.

When you install gunite jet bodies, the trick is to set the wall fitting slightly forward of the forms, because it needs to end up flush with your finished surface. Essentially, you’re allowing for the tiles and adhesive. See how to install gunite jet bodies.

Concrete pour day for the walls

With the forms built, it was finally time to pour the walls.

Before the pour, one more word on bracing. When you pour concrete, the weight is immense, and if your forms aren’t sturdy enough, your walls will bow. That causes major problems down the line, so it’s worth putting the time and effort into strong forms.

Pouring concrete is a messy job, but a very satisfying one. Doug had the concrete delivered to his driveway and wheeled it in by hand. That’s a lot of hard work, but it’s a cost-effective option.

Once the concrete is in the forms, it needs to be vibrated properly to remove air bubbles and make sure it fills every gap. The right tool for walls is a concrete vibrator (a poker vibrator) pushed down into the concrete. A vibrating plate is for compacting gravel, not for walls.

Once poured, the concrete needs to cure for a few days before the forms come off.

A rocky road: walls, seats and a damaged jet

This part of the build was a bit of a rollercoaster.

The good news: Doug poured the walls successfully. The forms held up well, and the concrete looks great. He also started on the interior seating using CMU blocks.

The bad news: a CMU block fell from the top of the hot tub and damaged one of the jet fittings. It’s a common accident, and a reminder to be extra careful with heavy materials around your plumbing.

The solution: rather than trying to replace the damaged jet fitting, which could have caused more problems, we decided to build up the wall around it and cover it with the jet holder. That gives a clean, professional finish.

Moving forward: Doug carried on with the interior seating and started forming the steps. Once the steps had cured, he could move on to waterproofing. For step ideas, see hot tub steps: the ultimate guide.

DIY projects are challenging, and setbacks are bound to happen. The key is to stay positive and find a solution to each problem as it comes up.

Backfilling around the pipework

Next, a crucial step that’s often overlooked: backfilling around the pipework. It matters for the long-term stability of the hot tub.

Why backfilling matters: it supports your plumbing, preventing damage from shifting soil or ground movement. It also levels the area around your hot tub, giving a stable base for a patio or decking.

The right material: the best backfill is rock or a Type 1 style crushed gravel. Avoid using dirt, because it can settle over time and put pressure on the pipes.

The process:

1. Dig a trench: carefully dig a trench around your pipework, making sure the pipes are securely supported.
2. Fill with gravel: fill the trench with rock or gravel, packing it in firmly around the pipes.
3. Add a membrane: for extra protection, consider laying a membrane over the gravel before the final layer of stone.

Additional tips:

• If you’re planning a patio or deck, level the backfilled area to suit.
• Consider a French drain to deal with water drainage.
• If you’re running electrical or other cables, put them in conduit to protect them.

Doug did a great job here. He backfilled around his pipework, prepared for a French drain, and ran conduit for electrical and ethernet cables, which is a great way to future-proof the tub. I’m impressed with his attention to detail.

Grounding for local code

Next up was grounding. Doug’s local authority requires it, and it would be inspected. What was different about Doug’s build was that his code required two complete loops around the outside of the tub, like in the image below.

This is the first time I’ve seen this, but each town or city has its own code. The loops are connected to the rebar structure, and there are 4 ground rods driven 3 feet into the ground. The control room, and anything electrical, is also connected to the grounding. It’s a bit technical, but it’s required to meet local code, so always check with your own inspector. There’s more on the rules in hot tub wiring explained.

Waterproofing with Hydro Ban

With the grounding in and the inspection passed, it was on to waterproofing. Doug used my favourite waterproofing product for US builds, Hydro Ban from Laticrete, a liquid-applied rubber membrane. It’s a great product and easy to get hold of.

It goes on all the internal surfaces of the tub, like the walls and seating. Apply the first coat in one direction (say, left to right) and let it dry, then apply the next coat at 90 degrees to it (top to bottom), following Laticrete’s instructions on coverage and drying times. Once that’s done, the tub will be watertight. For the full picture, see hot tub waterproofing, tile adhesive and grout.

Patio, fire pit and deck

After waterproofing, the membrane needs time to cure. So while Doug waited, he turned to the area around the tub.

Most DIY hot tubs are part of a bigger garden renovation, and Doug’s was no exception. He planned a patio with a fire pit. He laid gravel and compacted it, then added slab stones on top to create a patio that sits lower than the tub, so he gets the drop from the infinity edge. With the fire pit and seating area, it’s going to look wonderful.

With the patio done, it was on to the decking. There’s a huge amount of timber in the raised deck, which will be level with the existing deck, so it all fits together perfectly. Doug told me it took a couple of days to put this together. He planned to leave it exposed until the inside of the tub was finished. For ideas, see hot tub deck ideas.

The control room

With the patio done, it was time to move on to the control room. In the picture below, you can see its base. The pipes are already in the ground and just need connecting.

Where you put the control room is very important, and it’s all about the water line. Standard hot tub pumps aren’t self-priming, so they need to sit below the water line, where water flows to them by gravity. In Doug’s build, the patio is basically at the water line. His pumps and pipework are below it, so there’s no issue. That means he can use hot tub parts, which are a lot cheaper, and it lets him use bigger pumps. See hot tub control room position and self-priming hot tub pump options for when that isn’t possible.

The big pipe in the middle of the picture leads to the French drain. It makes sure groundwater is carried away rather than sitting there. He’s done the same for the control room, which is a great idea: if water does get in, it has somewhere to go.

The control room has to be covered, because hot tub equipment isn’t built to sit out in the weather the way swimming pool equipment is. This is where it stood after the final pour.

The control room enclosure, and a patio rethink

Fast forward a few months, and Doug was ready for the next phase: building the enclosure for the control room. Doug used a mix of hot tub and swimming pool parts. The pool parts are designed to cope with outdoor conditions, but the hot tub components need protecting from the elements, and that’s what this structure does. Below you can see the timber structure that will house the whole setup. I cover the do’s and don’ts of mixing the two in can I use pool parts on a hot tub?

Just when Doug thought he was making progress, he realised he wasn’t happy with the layout of the infinity trough and patio. The trough was too close to the patio, which made the whole thing look awkward. So what did Doug do? In true DIY fashion, he tore it all up and started again.

He dug down another 8 inches, re-levelled the area and relaid the whole patio. You can see the new layout below, and it looks fantastic. I can only imagine how frustrating it was to redo all that work, but that’s the reality of DIY hot tub building. Sometimes you take two steps forward and three steps back before you get it just right.

With the fire pit area finished and looking great, Doug turned back to the control room. Inside, he’s installed a variable speed pump for the infinity edge, a hot tub circulation pump and a sand filter. He chose a sand filter because of the larger size of the hot tub, as it handles the bigger volume of water well. See can I use a variable speed pump in a hot tub? and can I use a sand filter on my DIY hot tub?

Next up for Doug: tiling and the finishing touches on the inside of the tub. We’re getting close to the finish line, so stay tuned.

Planning your own infinity hot tub or swim jet?

My infinity hot tub CAD plans come in a range of sizes and include CAD drawings, the plumbing for the overflow edge and balance tank, a parts list and the video course. If you want something bespoke like Doug’s, my custom hot tub design consultancy gets you a design and my support through the build.

To add a swim jet, I sell the counter current swim jet with pump, the dual pump version and the jet without a pump. The fitting is covered in how to install a counter current swim jet.

FAQs

Can you put a swim jet in a hot tub?

Yes, if the tub is long enough to swim against the current. Doug’s is designed around one from the start. The swim jet I sell needs a pool or tub at least 4m (14ft) long.

What strength concrete should I order for a hot tub?

I ask for 4,000 PSI, without added air. Fibres and a waterproofing admixture help if your supplier offers them.

Why do the forms need so much bracing?

Wet concrete is extremely heavy and pushes hard on the forms. Without strong bracing, the walls bow.

Does a hot tub control room need to be below the water line?

For standard hot tub pumps, yes, because they aren’t self-priming. If yours has to sit higher, you need self-priming pumps or a priming arrangement.

Got a question about an infinity or swim jet build like Doug’s? Drop 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