Hot Tub vs Plunge Pool: Which Should You Build in 2026?

Last updated: September 2026

Hot tub or plunge pool: which one should you build? This question lands in my inbox almost every day. The honest answer is that there’s no right or wrong. It comes down to how you’ll use it, the space you’ve got and your budget.

I’ve helped people build both (and plenty of combinations of the two), so in this post I’ll break down the real differences: size, temperature, plumbing, cost, safety and upkeep. By the end, you’ll have a much clearer idea of which is right for you.

What is a plunge pool?

A plunge pool is a compact swimming pool built for cooling off, wading and relaxing rather than swimming lengths. There’s no strict definition, but most are about 3–6m (10–20ft) long and 1.2–1.5m (4–5ft) deep, which is enough to stand with your shoulders under the water. Unlike a big pool, there’s usually no deep end and shallow end. The depth is the same throughout.

You’ll also hear them called dipping pools or cocktail pools. They can be left unheated, warmed by the sun, or heated with a heat pump or gas heater. A cocktail pool or “spool” usually adds benches, loungers and sometimes jets. For the full build, see How to build a DIY plunge pool and How to build a DIY cocktail pool or spool.

What is a hot tub?

A hot tub is built for hot water and hydrotherapy. The thing that really sets it apart is the jets, which keep the water moving and give you that massage. Many also have an air blower or a venturi system to add bubbles.

A hot tub typically runs at 37–40°C (98–104°F). The US Consumer Product Safety Commission says hot tub water should never exceed 104°F (40°C), and most spa packs won’t let you set it higher.

Hot tub vs plunge pool at a glance

	Hot tub	Plunge pool
Typical size	About 2–3m (7–10ft) square, ~1m (40in) of water, with seats	About 3–6m (10–20ft) long, 1.2–1.5m (4–5ft) deep
Water temperature	37–40°C (98–104°F)	Unheated, or heated to pool temperatures (often up to about 30°C / 86°F)
When you’ll use it	All year, and best in winter	Spring to autumn in cooler climates, most of the year in warm ones
Plumbing	Filter and heating circuit, plus one or more jet pumps and often a blower	Drains and skimmer, one pump, filter, optional heater
Build cost	Usually higher for the equipment, lower for the structure	More concrete, digging and tiles, but simpler equipment
Water care	Similar routine, at a higher sanitiser level	Similar routine, with more water to treat
Safety (USA)	A lockable safety cover can often replace a barrier	Usually needs a 48in (1.2m) barrier with a self-closing, self-latching gate

Size and space

The first and most obvious difference is size. A plunge pool tends to be bigger than a hot tub. That’s not always the case, but if you compare the two side by side, the plunge pool usually takes up more of the garden. A 2.44m (8ft) square hot tub fits where a plunge pool wouldn’t, so if space is tight, that may decide it for you.

Don’t forget the space around it either: steps, decking, somewhere for the cover, and the control room for the pumps and filter. See control room design considerations.

How you’re going to use it

This is the most important question of all, and it’s where the two really start to differ.

A hot tub is heated, so you can use it all year round whatever the weather. In fact, there’s nothing better than sitting in a hot tub in the middle of winter. That’s the whole point.

A plunge pool tends not to be heated to the same temperatures. It’s more of a pool for relaxing and cooling off, from spring through summer and into autumn. In a warm climate it’ll get a lot more use. In a cooler one, it’s more seasonal. Heat it with an air source heat pump and you can stretch the season a long way. Leave it cold and it doubles as a cold plunge. See How to build a DIY cold plunge pool.

I’ll be straight with you. I use my own hot tub as a plunge pool on the one or two days a year the UK gets properly hot weather. I turn the heating off, keep the jets ticking over gently, and it’s a great way to cool down. So a hot tub gives you some flexibility, because you can always run it cool. I’ve written up how in Can I use my hot tub as a swimming pool in summer? Heating a plunge pool to hot tub temperatures is a different matter entirely. It’s a much bigger volume of water, and a much bigger heating bill.

The plumbing

This is where the two differ most in complexity and cost.

Plunge pool plumbing

A plunge pool is relatively straightforward. Bottom drains and a skimmer feed the front of the pump. From there, the water goes through a filter, a heater if you have one, and back into the pool through the returns. It’s a swimming pool setup on a smaller scale. Clean, simple and effective.

Hot tub plumbing

A hot tub still needs that filtration and heating circuit, but on top of it you’ve got a completely separate system for the jets. As regular readers know, I work on a maximum of around 16 jets per pump, so depending on your design you may need more than one jet pump. You can also add an air blower, which pushes air into the jet bodies to give you that classic hot tub feel. That means more parts, more plumbing, more expense and more that can go wrong later. See How does hot tub plumbing work?

Where the pumps go

Hot tub pumps are centrifugal pumps. They can’t suck air, so they need to sit below the water line, where gravity keeps them primed. I recommend hot tub parts wherever they’ll do the job, to avoid what I call the “swimming pool tax”. That’s not a real tax, just the higher price that comes with pool-branded equipment.

A plunge pool gives you a bit more flexibility. If the pump is below the water line, a standard hot tub pump works fine. If the equipment has to sit above the water line, you need a self-priming pump, which is usually a swimming pool pump. See Hot tub control room position and the self-priming pump options.

Cost

Generally speaking, a hot tub costs more to build than a plunge pool of the same quality. The plumbing is more complex and the equipment list is longer. If you go for a quality heating solution like an air source heat pump or a gas heater, that can run into thousands of pounds or dollars before the build itself.

A plunge pool keeps the equipment simpler and cheaper. But it’s bigger, so there’s more digging, concrete, waterproofing and tiling, and those costs add up. For context on professionally installed plunge pools, Angi puts the US average at about $28,000, with most people paying $10,000–$40,000. In the UK, Checkatrade puts an in-ground concrete plunge pool at £15,000–£25,000 plus labour. Building it yourself costs a fraction of that, but the only way to know your number is to price your own parts list.

Running costs are closer than you might think. Both need filtering and sanitising every day. What really changes the bill is heating: how much water you’re heating, how hot, and for how much of the year. See the best way to heat a DIY hot tub.

Safety and water care

Barriers. In the USA, many areas base their rules on the International Swimming Pool and Spa Code (ISPSC). A pool typically needs a barrier at least 48in (1.2m) high with a self-closing, self-latching gate. Under the ISPSC, a spa or hot tub with a lockable safety cover complying with ASTM F1346 doesn’t need the same barrier. Your local code decides, so check with your building department. In the UK, there’s no general legal requirement to fence a private garden pool, but with children around I’d strongly recommend one, and a lockable cover on a hot tub. See Do I need a permit for my hot tub?

Water care. The routine is much the same for both: filter daily, test regularly, and keep the sanitiser and pH in range. Hot tubs run at higher sanitiser levels because they’re small, warm and busy. The CDC recommends at least 1ppm free chlorine in pools and at least 3ppm in hot tubs, with pH between 7.0 and 7.8. My full guide is Hot tub chemical levels.

Is there a best of both worlds?

If you’re still torn, you can combine them. Some of my favourite designs are a slightly larger plunge pool with a raised or sectioned-off area fitted with hot tub jets, or a hot tub and cold plunge side by side. You get the refreshing dip and the warm, therapeutic soak.

The key with any combo is to keep the hot tub and pool plumbing separate, so each can run at its own temperature and flow. I explain why in Why pool and hot tub plumbing should remain separate. For inspiration, see Hot tub pool combo: design considerations and Kyle’s cold plunge and hot tub combo.

So which should you build?

This is where I sit firmly on the fence, because the honest answer depends on you. Ask yourself three questions:

1. How do you want to use it? If you want something for year-round relaxation and hydrotherapy, build a hot tub. If you’re in a warm climate and mainly want somewhere to cool off in the warmer months, a plunge pool makes a lot of sense.
2. How much space do you have? If space is tight, a hot tub is usually the more compact option. Plunge pools are flexible on size, but they need a bigger footprint.
3. What’s your budget? Be honest with yourself. A hot tub needs more parts, more plumbing and more equipment. On a tighter budget, a plunge pool is usually the more cost-effective route, especially if you don’t heat it.

Whatever you choose, don’t feel you have to follow anyone’s rules. Build what suits your space, your budget and the way you live.

Planning your own build?

I have plans for both. My DIY hot tub plans come in a range of sizes, with CAD drawings, the plumbing layout, a parts list and the video course. For pools, there are plunge pool and cocktail pool plans from 12ft x 8ft and 15ft x 8ft up to 20ft x 10ft, each with metric dimensions too.

Want a combo or something that isn’t standard? Sketch it in the free Tub & Pool Designer Pro software, and I can turn it into architectural CAD and a 3D plumbing design. For a hot tub and pool combo, my combo design consultancy covers the whole thing.

For parts, my stores are parts4tubs.co.uk in the UK and parts4tubs.com in the USA.

FAQs

Is a plunge pool cheaper to build than a hot tub?

Usually the equipment is cheaper, because a plunge pool doesn’t need jet pumps or a blower. But it’s bigger, so you’ll spend more on digging, concrete, waterproofing and tiles. If you keep it unheated, a plunge pool is usually the cheaper option overall.

Can a plunge pool be heated like a hot tub?

You can heat it, and a heat pump will comfortably keep it at pool temperatures. Heating a plunge pool to 38–40°C is a much bigger job, because there’s so much more water, so it costs a lot more to run.

Can I use a hot tub as a plunge pool?

Yes. Turn the heating off or down in summer and it makes a great place to cool off. It’s smaller and shallower than a plunge pool, so no jumping or diving.

How deep is a plunge pool?

Most are about 1.2–1.5m (4–5ft) deep, enough to stand with your shoulders under the water. A hot tub has about 1m (40in) of water, with seats.

Does a plunge pool need a fence?

In most of the USA, yes: usually a 48in (1.2m) barrier with a self-closing, self-latching gate. Check your local code. In the UK it isn’t generally a legal requirement for a private pool, but it’s strongly recommended if children could get to it.

Still can’t decide? Tell me about your space in the comments below and I’ll give you my honest view.

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