Party Spas: How to Design a Big DIY Hot Tub for Entertaining

Last updated: September 2026

Party spas: are they a thing? They certainly are. A party spa is simply a big hot tub designed for a crowd, with enough seats for friends and family, jets for everyone, and the lighting and sound to make a night of it. And because you’re building it yourself, you can make it exactly the size and layout you want.

I help people design and build their own hot tubs, plunge pools and pools, and a surprising number of them want something bigger than the usual 6–8 seats. In this post I’ll cover what makes a party spa different, how big it should be, how to plumb and heat it, and how to keep a busy tub clean and safe.

What is a party spa?

A party spa is a hot tub designed for social gatherings. It’s the same thing as any other hot tub, just bigger, with more seats and features that suit a group:

• Ample seating: benches, corner seats and perhaps a lounger or two, so everyone can get in at once.
• Jets for everyone: well-placed jets at each seat, not just the “best seat in the house”.
• Lighting: colour-changing LED lights in the water and around the tub.
• Sound: outdoor speakers or Bluetooth audio.
• Drinks ledges or a wide coping to put things on.
• Easy controls: a simple topside panel plus app control, so anyone can turn the jets on.
• Durable finishes that can take heavy use.

Party spa, party pool or cocktail pool?

	Party spa	Cocktail pool / spool	Party pool
What it is	A large multi-seat hot tub	A small pool with benches, sometimes jets	A larger, shallow social pool
Water	37–40°C (98–104°F), about 1m (3ft 3in) deep with seats	Pool to hot tub temperature, 1.1–1.4m deep	Pool temperature, standing depth
Best for	Evenings and year-round soaking with friends	Summer and winter use in a small space	Summer days, kids and big groups

If a party pool sounds more like you, read Building a DIY party pool. For a pool that can be run both hot and cool, see how to build a cocktail pool or spool, and for a cooler pool alongside your spa, my DIY plunge pool guide.

Can I build my own party spa?

Absolutely. A party spa is built in exactly the same way as any other in-ground or raised DIY hot tub: a reinforced concrete slab, ICF or core-filled block walls, plumbing back to a control room, a pool-rated membrane and tiles. It’s just bigger, so there’s more of everything. The steps are:

1. Plan and design the layout, seats, jets, lighting and control room.
2. Check permits and rules, including electrics and any barrier requirements.
3. Build the structure: dig, slab, walls and seats. See how to build a DIY in-ground hot tub.
4. Plumb it: jets, drains, skimmer, returns and pumps, pressure tested before you backfill.
5. Waterproof and tile, with a flood test before tiling.
6. Electrics by a qualified electrician.
7. Fill, balance and commission, then test every pump, jet and light and check for leaks.

There’s a huge amount of free information on this site to help. Start with I want to build a hot tub: where do I start? and What makes a good DIY hot tub design?

What size should a party spa be?

• Available space. Measure the area, including room around the tub for steps, a walkway and the control room.
• Seating. How many people do you usually host? Build in a little extra for unexpected guests. Around 18in (45cm) of bench per person is the absolute minimum, and that’s shoulder to shoulder. For a comfortable soak, plan for noticeably more.
• Seat depth and height. Seats need to be deep enough to lean back and low enough that shoulders are under the water. Mixing heights suits adults and children.
• Intimate or lively? A smaller tub feels cosier. A bigger one takes more people but can feel empty with two in it.
• Running costs. Every extra foot adds water to heat, filter and treat.

As a guide, my standard plans for bigger tubs are 12ft x 10ft, 12ft x 12ft and The Kyle, a 15ft x 8ft dual-lounger design. They’re a good starting point for a party spa.

Design considerations

1. Seating mix. Benches for groups, corner seats, one or two loungers, and a step or low seat for children.
2. Jet placement. Target backs, shoulders and feet at every seat, and mix fixed and adjustable jets. See DIY hot tub jets.
3. Lighting and ambience. Underwater LEDs, plus perimeter and step lighting for safety. See the ultimate guide to hot tub lights and my super slim spot light 4-pack.
4. Audio. Use marine-grade outdoor speakers mounted outside the tub, and keep all mains-powered kit well away from the water. Bluetooth from a phone kept dry is the simplest option.
5. Drinks and storage. A wide coping or ledge for drinks (plastic glasses only), and somewhere dry for towels.
6. Layout and flow. Wide, safe steps with a handrail, and space to get in and out without climbing over people. See the ultimate guide to hot tub steps.
7. Privacy. Screens or planting. See hot tub privacy ideas.
8. Fitting into the garden. Decking or paving that suits the space. See hot tub deck ideas.

Plumbing considerations

A party spa sees more bathers at once, so the plumbing has to keep up.

• Jet pumps. As a rough guide, one jet pump runs up to about 16 jets. A big tub with jets at every seat may need two or three, each on its own circuit, so you can run one zone or all of them. See how many pumps do you need? and how to size a hot tub pump.
• A separate circulation pump for filtration, heating and sanitising, so the water is treated without the jet pumps running. See how to add a circulation pump.
• A bigger filter, or more than one. More people means more oils, suncream and debris. See cartridge or sand filter?
• Twin main drains per pump suction, with anti-entrapment covers. The more powerful the pumps, the more this matters. In the USA, the VGB Act requires ANSI/APSP/ICC-16 drain covers. See installing a main drain.
• Air. A blower or venturi air adds the bubbles people expect. See air blower or venturi?
• Access. Put every valve, union and joint where you can reach it. Make the control room bigger than you think. See control room design considerations.

Heating a big tub

For scale, my own tub holds about 2,800 litres. With a 3kW spa heater, it took around 40 hours to heat from cold in December. A party spa can easily hold twice that or more. Raising 6,000 litres by 10°C (18°F) takes about 70kWh of heat, which is over 23 hours from a 3kW heater even with no heat loss.

So for a party spa, I’d use an air source heat pump to do the heavy lifting, with the spa pack heater as a top-up. The US DOE puts pool heat pumps at a COP of 3 to 7. See the guide to air source heat pumps for hot tubs and how to choose the right one. Insulate the walls and floor (ICF helps), and get a good insulated cover. It’s big, so consider a split cover that’s easier to lift. See DIY hot tub insulation and the ultimate guide to hot tub covers.

Keeping a busy tub clean

• Keep the sanitiser up. The US CDC recommends at least 3ppm free chlorine in hot tubs, pH 7.0–7.8, and no cyanuric acid stabiliser, tested at least twice a day, and more often when lots of people are using it.
• Shock after a party. See hot tub shock explained.
• Ask everyone to shower first. It makes a real difference.
• UV-C on the circulation line adds a layer of treatment for a heavily used tub, but it doesn’t replace a residual sanitiser. I don’t think you need ozone. See why you don’t need ozone.
• Clean the filters more often than on a normal tub. See how to clean a hot tub filter.

The full ranges are in my hot tub chemical levels guide. If you’re building one for a holiday let or for paying guests, different rules apply. See domestic vs commercial hot tubs.

Safety

• Temperature. The US CPSC says hot tub water should never exceed 104°F (40°C), and pregnant women should keep to 100°F (38°C). It also warns that drinking alcohol before or while hot tubbing can cause drowsiness and drowning. That’s worth remembering at a party.
• Barriers. The CPSC’s barrier guidelines include spas and hot tubs in the definition of a pool, with a 48in barrier and self-closing, self-latching gates. Some codes accept a lockable safety cover on a spa instead, so check locally. In the UK there’s no legal requirement for a private tub, but a lockable cover is a must, and RLSS UK recommends secure fencing at least 4ft high around home pools.
• Non-slip surfaces, a handrail and good lighting on the steps.
• Supervise children at all times, especially when the adults are distracted.
• Electrics by a qualified electrician: a dedicated RCD-protected supply under BS 7671 Section 702 and Part P in the UK, and GFCI protection and bonding under NEC Article 680 in the USA. See hot tub wiring explained.

Common party spa mistakes

• Too many jets for the pumps, so every jet is weak.
• No circulation pump, so the big jet pumps run for hours just to filter.
• Relying on a 3kW heater to heat a very large tub.
• Seats that are too narrow or too high.
• A cover too heavy for one person to lift.
• A control room with no space to work.

Planning your own party spa?

My DIY hot tub plans come in a range of sizes, including the bigger 12ft x 10ft and 12ft x 12ft designs and The Kyle (15ft x 8ft). Each gives you CAD drawings with every dimension, the plumbing layout, a parts list and the video course.

Want something truly custom? Sketch it in the free Tub & Pool Designer Pro software, and I can turn it into architectural CAD and a 3D plumbing design, or design it with you through the custom hot tub design consultancy. Adding a party spa to a pool? See my hot tub pool combo guide.

FAQs

What is a party spa?

A large hot tub designed for groups, typically seating eight or more, with jets at every seat, lighting, sound and somewhere to put your drink.

How big should a party spa be?

Big enough for your usual group plus a couple of extra seats. Many people go for 10–15ft (3–4.5m). Allow at least 18in (45cm) of bench per person as an absolute minimum, and more for comfort.

How many pumps does a large hot tub need?

As a rough guide, one jet pump for every 16 or so jets, plus a separate circulation pump for filtration and heating.

What’s the best way to heat a big hot tub?

An air source heat pump doing most of the work, with the spa pack heater as a top-up, plus insulation and a good cover.

Is a party spa the same as a party pool?

No. A party spa is a large hot tub at 37–40°C. A party pool is a larger, shallow pool at pool temperature.

Planning a party spa? Tell me about 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