Plunge Pool and Hot Tub Combo: How to Design One Project That Does Both

More and more of the emails I get start the same way: “I can’t decide between a hot tub and a plunge pool, so can I have both?” You can. A plunge pool hot tub combo gives you somewhere to cool off in summer and somewhere hot to soak in winter, in one project, one dig and often one control room. But decisions you make on paper decide how well it works for years, so in this post I’ll cover the layouts that work, the one rule I won’t bend on, and sizes, heating, safety and cost.

What is a plunge pool hot tub combo?

It’s any project that puts a jetted hot tub and a plunge pool (warm, unheated or cold) together as one design. If you’re still deciding which of the two you really want, start with my comparison hot tub vs plunge pool: which should you build in 2026? This post assumes you want both.

A quick refresher on the two halves. A hot tub runs at 37–40°C (98–104°F) and is all about the jets. A plunge pool is a small pool for cooling off and relaxing, usually 3–6m (10–20ft) long and 1.2–1.5m (4–5ft) deep, with the same depth throughout. The trick with a combo is letting each one do its own job properly.

Four plunge pool hot tub combo layouts that work

1. A raised hot tub spilling into a plunge pool

This is the classic look you’ll see in magazines: the hot tub sits slightly higher at one end of the pool and its water flows over a lip or through a spillway into the pool below. It looks fantastic and it’s great for entertaining.

The catch is that the two bodies of water are connected. Every litre that spills over carries heat into the pool, so running the spillover while you’re trying to keep the hot tub at 38°C (100°F) costs you money. I’ve covered the design details in adding a spillover hot tub to an existing pool.

2. Two separate tubs side by side

The simplest and, in my view, the most practical option for most DIYers. You build a hot tub and a plunge pool (or a cold plunge) next to each other, sharing a surround, a set of steps and a control room, but with completely separate water. Each can run at its own temperature and each can be drained, cleaned and serviced on its own.

This layout is also the best fit for the hot-and-cold routine that’s become so popular: a soak in the hot tub, a short dip in the cold plunge, then back again. My guide to building a DIY cold plunge pool covers sizing, walls, chillers and safety for the cold side.

3. A plunge pool with a jetted hot tub zone

Here the plunge pool itself gets a bench or a sectioned-off corner fitted with hot tub jets. It’s one body of water, so it’s cheaper to build than two tubs, and you get a massage seat in a pool you can move around in. What you don’t get is true hot tub temperatures, because heating the whole pool to 38°C (100°F) would be a much bigger heating bill. Think of this as a warm spa-style pool rather than a hot tub.

4. One tub that switches between hot and cold

A single deep tub with both a heater and a chiller, so you can run it as a hot tub in winter and a cold plunge in summer. It saves space, but you only get one temperature at a time, and swinging between hot and cold takes time and energy. Kyle’s project is a good example of how it can be done: see DIY cold plunge and hot tub combo: Kyle’s backyard wellness centre.

The golden rule: keep the plumbing separate

Whatever layout you choose, my advice is the same: give the hot tub and the pool their own suction, their own pumps, their own filtration and their own heating. Here’s why.

• Different temperatures. A hot tub wants 37–40°C (98–104°F). A plunge pool is usually unheated or kept at pool temperatures, and a cold plunge runs far colder. One system can’t hold two temperatures.
• Different flows. A hot tub’s jets need a lot of water moving through relatively short pipe runs. I work on a maximum of around 16 jets per pump. A pool just needs steady filtration and turnover.
• Different water care. Hot tubs are small, warm and busy, so they run higher sanitiser levels than a pool.
• Easier to live with. You can drain or fix one side while the other keeps working.

Large swimming pool and spa combos in the US often share one set of equipment and use motorised valves to switch between “pool mode” and “spa mode”. That works on a big pool with automation, but on a DIY combo it adds cost and complexity, and the hot tub still loses heat whenever the water is shared.

If you do want a spillover, the usual approach is to run it only when you want the look, and to keep the hot tub’s own circuit doing the heating and jets the rest of the time. [ANDI: add how you plumb and control a spillover on the combos you design]

Sizes, depths and water volume

Size drives the dig, the equipment and above all the heating bill. As a rough guide:

• Hot tub: about 2–3m (7–10ft) square with around 1m (40in) of water and bench seats. An 8ft x 8ft (2.44m x 2.44m) tub is the size most people build.
• Plunge pool: about 3–6m (10–20ft) long and 1.2–1.5m (4–5ft) deep, so you can stand with your shoulders under the water.
• Cold plunge: small and deep, sized for one or two people to stand or sit shoulder-deep.

To give you a feel for the volumes, a 12ft x 8ft (3.66m x 2.44m) plunge pool at 4.5ft (1.37m) deep holds roughly 3,200 US gallons (about 12,200 litres). An 8ft x 8ft hot tub with 40in (1m) of water holds roughly 1,600 US gallons (about 6,000 litres) before the seats take up some of that. That’s about twice the water, which is why heating the pool to hot tub temperatures isn’t realistic for most people. If you want the drawings for the pool side, my 12ft x 8ft plunge pool plans include architectural drawings, and there’s a 14ft x 10ft version too.

Heating and cooling each side

The hot tub needs a heater that can hold 37–40°C (98–104°F). A spa pack’s electric heater does the job, and many people add a heat pump or gas heater. The US Consumer Product Safety Commission advises that hot tub water should never go above 40°C (104°F).

A warm plunge pool can be left unheated, warmed by the sun, or heated with a heat pump to pool temperatures, often up to about 30°C (86°F), to stretch the season.

A cold plunge needs a chiller. Most cold plunge guides suggest water somewhere around 10–15°C (50–59°F), and anyone with a heart condition or other health concerns should check with their doctor before cold water immersion.

Cover both tubs when not in use: an insulated cover is the cheapest way to cut heat loss on the hot side and heat gain on the cold side.

The control room and electrics

A combo usually means two sets of equipment, so plan a bigger control room early. Hot tub pumps are centrifugal pumps that can’t pull air, so they need to sit below the water line to stay primed. If the equipment has to sit above the water line, you’ll need a self-priming pump, which is usually a swimming pool pump.

On electrics: two heaters, several pumps and possibly a chiller add up to a significant load. The supply, protection, and bonding or earthing of both tubs and all metalwork must be designed and installed by a qualified electrician, and local regulations apply in both the UK and the US. This isn’t a DIY job.

Safety, barriers and permits

In much of the US, local rules are based 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. A hot tub with a lockable safety cover meeting ASTM F1346 can often avoid the barrier, but once your project includes a plunge pool, expect the barrier rules for pools to apply to the whole area. Your building department has the final say.

In the UK there’s no general legal requirement to fence a private garden pool, but with children around I’d strongly recommend a barrier plus lockable covers. Depending on size, position and any raised structures, you may also need planning permission or building regulations sign-off, so check with your local council before you dig. Structural questions, such as a raised hot tub wall or a tub near a building, should go to a structural engineer.

What does a plunge pool hot tub combo cost?

There’s no single number, because a combo is really two projects sharing a site. The pool side is mostly structure (digging, concrete, waterproofing, tiles); the hot tub side is mostly equipment (jet pumps, blower, heater).

For context, Angi puts the average professionally installed plunge pool in the US at about $28,000, with most people paying $10,000–$40,000, and Checkatrade puts an in-ground concrete plunge pool in the UK at around £15,000–£25,000 plus labour (2026 figures, and prices vary a lot by region). Building it yourself costs a fraction of that, but the only way to know your number is to price your own parts list.

Which layout should you choose?

• You want hot and cold routines: two separate tubs side by side.
• You want the wow factor for entertaining: a raised hot tub spilling into a plunge pool, with separate plumbing.
• You’re on a tighter budget: a plunge pool with a jetted seating area, run warm rather than hot.
• You’re short on space: one tub that switches between hot and cold.

If your idea doesn’t fit neatly into any of those, that’s normal. That’s what my  architectural CAD and plumbing design service is for: I draw the whole project around your site, with the plumbing for both sides laid out properly.

FAQ

Can a hot tub and plunge pool share the same water?

They can, as in a spillover design, but the hot tub loses heat whenever water flows between them. For most DIY builds I recommend separate plumbing and equipment.

Can I heat a plunge pool to hot tub temperature?

Technically yes, but it holds far more water than a hot tub, so the heating bill is much higher.

Do I need two sets of equipment for a plunge pool hot tub combo?

Usually, yes: separate pumps, filters and heating for each side. You can share a control room, a surround and an electrical supply designed by a qualified electrician.

Do I need a fence around a plunge pool hot tub combo?

In most of the US, a pool needs a barrier at least 48in (1.2m) high with a self-closing, self-latching gate, and that usually covers the whole combo. In the UK it isn’t generally a legal requirement for a private garden, but it’s strongly recommended with children around. Always check your local rules.