Backyard Swim Spa: Everything You Need to Know (Sizes, Costs and DIY)

Last updated: September 2026

Backyard swim spa? Yes please! A swim spa gives you somewhere to swim, exercise and relax all year round, in a fraction of the space of a pool. It’s one of the most popular things people ask me about, usually followed by “how much?” and “can I build one myself?”

This is my overview: what a swim spa is, the sizes, the choice between buying and building, what to plan for (base, electrics, access, safety), running costs and water care. Where a topic needs more depth, I’ll point you to the detailed guide.

What is a backyard swim spa?

A swim spa is a cross between a swimming pool and a hot tub. It’s a long, heated tub with a powerful current at one end, so you can swim against it without ever reaching the far wall. Many also have a hot tub seating area, and “dual-zone” models keep the swim area and the spa area at different temperatures.

People use them for:

• Swimming on the spot, at a pace you control.
• Aqua exercise, such as water walking, jogging and resistance work, which is easy on the joints.
• Relaxing in the seats or loungers, like a hot tub.
• Family time. It’s a small pool for the kids in summer.

Swim spa, hot tub, plunge pool or pool?

	Swim spa	Hot tub	Plunge pool	Swimming pool
Can you swim?	Yes, on the spot against the current	No	Only with a swim jet	Yes
Typical length	10–21ft (3–6.4m)	7–10ft (2–3m)	10–20ft (3–6m)	Much longer
Temperature	Adjustable. Dual-zone models run the spa area hotter than the swim area	37–40°C (98–104°F)	Unheated to ~30°C	Usually unheated or warm
Year-round use	Yes, with a good cover	Yes	If heated	Usually seasonal

How big is a swim spa?

According to HomeGuide, swim spas range from 5 to 10ft wide and 10 to 21ft long, are usually 3½–5ft deep and hold 1,300–2,500 gallons. Angi says most are at least 8ft wide. Filled, they can weigh over 20,000lb (about 9 tonnes).

• Around 12–14ft (3.7–4.3m): compact models, fine for aqua exercise and a gentle swim.
• Around 15–17ft (4.6–5.2m): the sweet spot for most families. There’s room for a proper swim area and a few seats.
• 18ft (5.5m) and over: usually dual-zone, with a separate hot tub section.

For swimming, length matters more than anything. If the swim area is too short, the current bounces back off the far wall. My swim jet considerations guide covers how long and deep the swim area needs to be.

Buy one or build one?

This is the big decision. Here’s how they compare:

	Shop-bought swim spa	DIY swim spa
Typical cost	$20,000–$40,000 installed (USA, HomeGuide). £10,000–£55,000 for the unit (UK)	Under $20,000 is realistic (my estimate), depending on size and finish
Time	Days, once the base and electrics are ready	Weeks to months of your own time
Size and shape	Fixed models	Whatever fits your garden
Access	Needs a clear route or a crane	Built in place, so access is rarely a problem
Finish	Acrylic shell in a cabinet	Tiled, set flush in the ground or raised
Warranty	Manufacturer’s warranty	Individual equipment warranties. The build is on you.

There’s a full price breakdown, including delivery and installation, in What does a swim spa cost?

Can I build my own swim spa?

Yes. A DIY swim spa is really a small cocktail pool or spool with a counter current swim jet added. The process is the same as building an in-ground hot tub, just longer: a reinforced slab, ICF or core-filled block walls, the plumbing and swim jet, a pool-rated membrane, a flood test and tiles.

It’s a big project, so be honest with yourself about the parts that need real care. The structure has to hold many tonnes of water without cracking. The swim jet needs its own pump and pipework. And the electrics should be done by a qualified electrician. It’s perfectly normal to do most of it yourself and hire in a digger, a bricklayer or a concrete pump.

Start with Can I build a DIY swim spa? and How to build a DIY exercise pool. For the groundwork, see my DIY in-ground hot tub build guide. And you can see a real one in Darren’s DIY hot tub and swim spa.

The swim current

Most swim spas create the current with jets. Some bought models use a propeller or hydraulic system instead, which gives a smoother current and costs more. On a DIY build, the current comes from a counter current swim jet set into the end wall, driven by its own dedicated pump.

Can you add a swim jet later? To a DIY pool or plunge pool, yes, if the pool is long enough and you can get the pipework to it, but it’s far easier to build it in from the start. To a shop-bought acrylic spa, it isn’t really practical. Buy the swim spa you want. See how to install a counter current swim jet.

Planning: base, electrics, access and permits

The base

A full swim spa can weigh 9 tonnes or more, so it needs a level, properly designed base, usually a reinforced concrete slab. For a bought model, follow the manufacturer’s specification to the letter, as a poor base can void the warranty. See how to build a concrete slab for a hot tub.

Electrics

Swim spas draw a lot of power, especially dual-zone models.

• UK: A dedicated circuit with at least a 30mA Type A RCD, SWA cable for the outdoor run, and a local isolator visible from the spa but at least 2m from it. It’s notifiable under Part P, so use a registered electrician.
• USA: A dedicated 240V circuit with GFCI protection, a disconnect within sight, and bonding under NEC Article 680. HomeGuide puts the electrical work at $800–$1,600.

There’s more in Hot tub wiring explained.

Access and delivery

A bought swim spa arrives in one piece, so measure the route from the road to the garden, including gates, corners and overhead cables. If it won’t fit, you’ll need a crane. Angi puts crane delivery at $800–$1,500 or more. A DIY build avoids this completely.

Permits and safety

Many US areas treat a swim spa like a pool, so expect a permit and a barrier, or in some places a locking safety cover. The CPSC’s barrier guidelines apply to spas and hot tubs too: a barrier at least 48in high, self-closing and self-latching gates, or a powered safety cover meeting ASTM F1346 in some situations. In England, a freestanding swim spa is usually treated like a hot tub, but sunken installations, decking or a building over it may need checking with your council. See Do I need a permit for my hot tub?

Running costs

Heating is by far the biggest ongoing cost, followed by chemicals, filters, repairs and eventually a new cover. Angi estimates $20–$50 a month in electricity for a small swim spa. In the UK, it depends heavily on your tariff, how warm you keep it and how well it’s insulated.

The biggest savings come from:

• A good cover. The US Department of Energy says covering a pool can cut heating costs by 50–70%, because evaporation is by far the biggest source of heat loss. See my guide to hot tub covers.
• An air source heat pump instead of a direct electric heater. See the ultimate guide to air source heat pumps for hot tubs.
• Insulation, whether that’s a well-insulated cabinet on a bought spa or ICF walls on a DIY build.

Keeping the water clean

A swim spa needs the same water care as a hot tub, just more of it:

• Filtration: clean the cartridges regularly and replace them when they wear. See how to clean a filter cartridge.
• Sanitiser: the CDC recommends at least 1ppm free chlorine in pools and at least 3ppm in hot tubs. A swim spa sits in between, so if you keep it warm, work to the hot tub level. Bromine at 4–6ppm is the alternative.
• Balance: pH 7.2–7.6 and total alkalinity 80–120ppm. My guide to balancing hot tub chemicals explains each step.
• Shower before you get in, and shock after heavy use.

Common mistakes

• Buying on gadgets rather than insulation and cover quality.
• Not checking delivery access until the crane quote arrives.
• Pouring a base that doesn’t meet the manufacturer’s spec.
• A swim area that’s too short for a proper swim.
• On a DIY build, adding the swim jet as an afterthought.

Planning your own swim spa?

My swim spa plans come in a range of sizes, with a swim area plus a hot tub seating section. You get the CAD drawings, plumbing diagrams, parts list, installation guide and video course.

For the current itself, I sell counter current swim jets in four versions:

• Swim jet: faceplate, body and tubes only
• Swim jet with no pump
• Swim jet with pump
• Swim jet with dual pump

Got an odd-shaped garden or your own design? Draw it in the free Tub & Pool Designer Pro software, and I can turn it into architectural CAD and a 3D plumbing design.

FAQs

How much does a backyard swim spa cost?

In the USA, Angi puts the average at about $22,500 before installation, and HomeGuide says $20,000–$40,000 installed. In the UK, new swim spas run from about £10,000 to £55,000. The full breakdown is in What does a swim spa cost?

How long does a swim spa need to be to swim in?

For proper swimming, look at 14ft (4.3m) or longer, so the current doesn’t bounce back off the far wall. Shorter models are better for aqua exercise.

Can a swim spa go in the ground?

Many bought models can be partly or fully recessed, but you need access to the equipment around the sides, so check the manufacturer’s instructions. A DIY swim spa is built in the ground from the start.

Do I need a permit for a swim spa?

In much of the USA, yes, plus a barrier or a safety cover. In England, usually not for a freestanding one, but check if you’re sinking it, building over it or in a listed building or conservation area.

How long does a swim spa last?

HomeGuide puts the average at 8–15 years, depending on quality and how well it’s looked after.

Can I build my own swim spa?

Yes. It’s a small pool with a swim jet, built like an in-ground hot tub. With good plans, I reckon under $20,000 is achievable.

Weighing up a swim spa? Ask me anything 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