How to Build a DIY Cocktail Pool or Spool: Step-by-Step Guide

Last updated: September 2026

Building your own cocktail pool, or “spool” as they’re often affectionately called, isn’t as difficult as you might think. If you can build an in-ground hot tub, you can build one of these. It’s the same method, just a bit bigger. In this guide I’ll cover everything you need to decide, and then walk through the build step by step.

What is a cocktail pool?

At its most basic, a cocktail pool is a small swimming pool. It’s a pool in every way apart from its size. So where does the “cocktail” part come from? You’re not going to be doing laps in it. You’re far more likely to be relaxing with a drink in your hand.

There’s no official definition, but most cocktail pools are around 10–16ft (3–5m) long, 6–10ft (2–3m) wide and 3½–4½ft (1.1–1.4m) deep. There’s no deep end, and they comfortably seat a small group. Built-in benches, sun shelves and loungers are what make them feel different from a plunge pool.

What’s a spool?

Cocktail pools often borrow features from hot tubs, such as heating, jets and air blowers. Combine “spa” and “pool” and you get “spool”. Essentially, a spool is a 12ft by 12ft super-sized hot tub. Because you control the temperature, you can use it both ways: a warm soak in winter and a cool plunge pool in summer. That sounds like the perfect combination to me.

If you want the background, I’ve written more in What is a spool? and Spool pool: a DIYer’s guide. This post is the full build guide.

	Hot tub	Cocktail pool / spool	Plunge pool
Typical size	7–10ft (2–3m) square	10–16ft (3–5m) long	10–20ft (3–6m) long
Depth	~3ft 3in (1m), with seats	3½–4½ft (1.1–1.4m), with benches and loungers	4–5ft (1.2–1.5m)
Water temperature	37–40°C (98–104°F)	Anything from pool temperature to hot tub temperature	Unheated to about 30°C (86°F)
Jets	Yes	Optional (yes if it’s a spool)	Usually no, but a swim jet is an option

If you’re more interested in a deeper pool for cooling off, or a swim jet, see my ultimate guide to building a DIY plunge pool.

Can I build a cocktail pool or spool myself?

Absolutely. The methods I use on this website for block and ICF hot tubs and plunge pools work perfectly for a cocktail pool. What you’re probably not going to do is shotcrete or gunite. That’s an art and really a job for a specialist crew. In its most basic form, you dig a big hole, lay a reinforced concrete slab, build walls about 4ft (1.2m) high around the perimeter, then plumb, waterproof and tile it.

Where people go wrong is treating it like a big hot tub structurally. A 12ft x 8ft cocktail pool, 4ft deep, holds about 2,900 US gallons (11,000 litres). That’s around 11 tonnes of water, roughly four times what my own tub holds. So the slab, rebar and walls need to be done properly, and on a deep pool or a tricky site it’s worth getting an engineer to check the design.

How much does a cocktail pool cost?

It’s always a difficult question. What it won’t cost you is the price of a full-size pool. For comparison, Angi’s 2026 guide puts a professionally installed plunge pool at an average of about $28,000, and Checkatrade puts a concrete in-ground plunge pool in the UK at £15,000–£25,000 plus labour.

Back in 2021, based on the large hot tub projects we’d worked on, my rough estimate was that a DIY cocktail pool should come in under $10K, and possibly around $7K if you kept costs as low as possible. Prices for concrete, steel and equipment have gone up since then, so treat those numbers as a floor, not a budget. The things that push the cost up are:

• The finish. Pool tiles cost more than a liner or render and paint.
• Jets and blowers, which need extra pumps, pipework and wall fittings.
• Heating. A heat pump costs more upfront but much less to run.
• What you hire in: digger, skips, concrete pump, bricklayer, electrician.
• The surroundings, such as decking, paving and fencing.

Running costs: in 2021 I estimated $1,000 a year at the low end and up to $3,000 if you heat it a lot. The real figure depends on how often you heat it, your climate, your energy tariff, insulation and whether you use a cover. A heat pump and a good cover are the two biggest savings.

Design decisions to make before you dig

Size and depth

The exact dimensions depend on your garden. Think about how many people you want to seat, where the benches and loungers go, and where the steps go. Remember that the hole is deeper than the water: add around 350–400mm (14–16in) for the slab, sub-base, waterproofing, tiles and freeboard.

Shape: square, round or kidney?

It comes down to how comfortable you are building shapes in block. A square or rectangular pool is far easier than a kidney or round one, both to build and to tile. The plumbing is the same whatever the shape, so pick something you can build well. If the shape you want is beyond your blocklaying skills, get a bricklayer in for a few days. It adds cost, but you know the walls will be spot on.

Benches, loungers and steps

These are what make it a cocktail pool. A bench around one or two sides at seated depth, a step-down entry and an in-water lounger are the classic features. My concrete lounger guide shows how to build one.

The control room

Where will the pump, filter, heater and any jet pump go? They need to be covered and out of the weather, close to the pool, and in a space with its own drain. A basic setup needs about 3ft (1m) square. For a heated spool with jets, allow more, because you need room to work on the equipment.

Heated or not?

This depends on when you plan to use it. Will you use it all year round, or do you live somewhere warm where you won’t need heat for months at a time? The bigger the pool, the more energy it takes to heat and the more it costs to run.

For scale, raising 11,000 litres (2,900 US gallons) by 10°C (18°F) takes about 128kWh of heat. A 3kW spa heater would take over 40 hours to do that even with no heat loss, which is why the small heaters used on hot tubs aren’t enough on their own.

Heating option	Pros	Cons
Air source heat pump	Cheapest to run, as it moves heat from the air rather than making it. Many models can also cool.	Higher upfront cost, and less output in very cold weather.
Gas or propane heater	Fast heat-up and works in any weather.	Expensive to run, and needs a gas supply or tank.
Electric heater (spa pack)	Cheap to buy and simple.	Slow and costly on a pool this size. Best used to top up a heat pump.
Solar	Free heat in summer.	Needs space and sunshine, with little output in winter.
Wood-fired	Off-grid and atmospheric.	Hands-on and hard to hold at a steady temperature.

In 2021 I reckoned an air source heat pump would add around $5K to the build, but prices vary a lot by size and brand, so get quotes for a unit sized to your pool. See how to choose the right air source heat pump for your hot tub or pool. And if you’ll run it at hot tub temperatures, the CPSC advises never going above 104°F (40°C).

Jets or no jets?

Decide at the design stage. The jets, pipework and gunite bodies go in during the build. You could add them afterwards, but it’s going to be messy.

The number of jets decides your pump. Each jet needs a certain flow, and the further the control room is from the pool, the more the pump has to push and pull. As a rough guide from our builds, up to about 16 jets can run on a single 4HP pump if it’s close to the pool. Your plans should set the exact figure. See how to correctly size a hot tub pump. Keep the jet circuit separate from the filtration circuit (see why pool and hot tub plumbing should remain separate).

The finish: tiles, liner or render?

The finish affects the cost, how long it lasts and how it looks.

• Tiles (mosaic or porcelain) on a pool-rated membrane cost the most but last the longest. They’re my preference.
• A liner is cheaper upfront, but it’ll need replacing every few years, and on a full-size pool a replacement is a few thousand. See Can I use a liner on my DIY hot tub?
• Render and pool paint is the budget option, but it needs repainting over time.

It’s absolutely possible to build a good-looking pool on a budget. Just factor in replacement costs.

Sanitising

Method	What to know
Chlorine	Cheap, effective and the most common. It can irritate sensitive skin.
Bromine	Gentler on skin and more stable in hot water. It costs more, and sunlight breaks it down, so use a cover outdoors.
Salt chlorination	Makes chlorine from salt, so the water feels softer. Salt is corrosive, so use salt-rated equipment and avoid soft natural stone.
UV-C or ozone	Reduce how much chemical you need, but don’t replace a residual sanitiser.

The US CDC recommends free chlorine of at least 1ppm in pools and 3ppm in hot tubs, with pH 7.0–7.8. If you run your spool hot, treat it like a hot tub. See Should I use bromine or chlorine?

Permits and safety barriers

UK: In England, an outdoor garden pool often doesn’t need planning permission, because it falls under permitted development. Check with your council if you’re in a listed building, a conservation area, a national park or other designated land. The electrics are notifiable under Part P. There’s no law requiring a fence around a private pool, but RLSS UK recommends secure fencing at least 4ft high, and I’d add a lockable cover.

USA: An in-ground pool almost always needs a building permit, an electrical inspection and a safety barrier. The CPSC’s barrier guidelines call for a barrier at least 48in high (5ft is preferable), no gaps a 4in sphere can pass through, and self-closing, self-latching gates that open away from the pool. Local codes vary, so check with your building department. See Do I need a permit for my hot tub?

My plunge pool guide has a full UK vs USA safety barrier comparison.

How to build a cocktail pool, step by step

This is a summary of the main stages, so you can see how much work is involved. The construction process is the same as an in-ground hot tub, just bigger.

Step 1: Clear and set out the area

Clear the site, check for buried services (use LinesearchbeforeUdig in the UK or call 811 in the USA), and mark out the hole with pegs and string lines. Check that the diagonals match so it’s square from the start.

Step 2: Dig the hole

Dig to the water depth plus the build-up underneath, with a little working room around the walls. Use a micro digger if it’ll fit. Mine was dug by hand, with a breaker for the clay, and it’s hard going. Don’t work in a deep hole with unsupported sides, and plan where the spoil is going before you start.

Step 3: The base: sub-base, drains, HRV, rebar and slab

Here’s the full sequence I’d follow:

1. Lay 100–150mm (4–6in) of compacted Type 1 sub-base, then sand blinding and a 1200-gauge DPM. I used a heavy pond liner, as you can see in the photo.
2. Fit the main drains and a hydrostatic relief valve. Use two main drains teed together, at least 1m (3ft) apart, with anti-entrapment covers. The valve stops groundwater pressure lifting or cracking the pool when it’s empty. See Installing a main drain and Why do I need a hydrostatic relief valve?
3. Tie a proper rebar grid on spacers, with starter bars up into the walls. The photo shows my first attempt, which was only a few bars. For a pool this size, you want a full grid. See my rebar guide.
4. Pour a reinforced slab of at least 150mm (6in) using ready-mix C25/C30 concrete, in one go. I mixed mine by hand from sand and cement, and I wouldn’t do that on a pool.

Step 4: Walls, benches and steps

Next come the walls, benches and steps. I used concrete blocks. Today I’d use ICF blocks, which dry-stack, take rebar inside, and are filled with concrete to give an insulated, reinforced wall. If you use block, choose hollow blocks with vertical rebar tied into the slab’s starter bars and core-fill them. Build the benches and steps at the same time.

Step 5: Plumbing

Run the suction lines from the main drains and skimmer, the return lines for filtered water, and a separate circuit for any jets. Use pressure-rated PVC and proper fittings, keep runs neat and square, and pressure test everything before it’s buried. Set the skimmer so the water level will sit about halfway up its mouth, and check the finished deck height first.

Step 6: Jets and wall fittings

Core drill the walls (or cut the ICF foam) and set the gunite bodies for jets, returns and lights. Glue the pipes into the bodies first, and keep every body square to the wall. See the ultimate guide to gunite jet body installation.

Step 7: Backfill, render, membrane and flood test

Backfill behind the walls with concrete or compacted fill once the pipework has been tested. Then render the walls, apply a pool-rated waterproofing membrane in two coats (such as Ardex S 7 Plus in the UK or Laticrete Hydro Ban in the USA), and flood test before you tile. See waterproofing, grout and tile adhesive.

Step 8: Tile and finish the surface

Tile on a pool-grade flexible adhesive and grout, then fit the coping. Leave everything to cure for as long as the data sheets say before you fill. On my build, that was three weeks.

Step 9: Electrics

Have a qualified electrician install a dedicated circuit with RCD (UK) or GFCI (USA) protection, the isolator or disconnect, and equipotential bonding, which needs to be tied into the rebar before you pour. In the UK, pools fall under BS 7671 Section 702. In the USA, NEC Article 680 requires bonding of the rebar and the perimeter surface with 8 AWG solid copper. See A guide to hot tub electrics.

Step 10: Fill, commission and enjoy

Fill it, watching for leaks as the water reaches each fitting. Then start the pumps, check every joint in the control room, balance the water chemistry and bring it up to temperature. Now grab yourself a cocktail. You’re done.

Common cocktail pool mistakes

• Building the structure like a small hot tub and under-reinforcing it for the extra water.
• Leaving out the hydrostatic relief valve, or fitting only one main drain.
• Deciding on jets or heating after the walls are up.
• Using a small spa heater as the only heat source.
• Skipping the flood test, or filling before the tile adhesive has cured.
• No safety barrier or lockable cover.
• A cramped control room with no drain.

If you do end up with a leak, see how to detect and fix a leak.

Planning your own cocktail pool?

My plunge pool / cocktail pool plans include architectural drawings (plan view and side elevation), plumbing layouts for both hot-tub-style and traditional pool setups, steps and a lounger area, the Ultimate DIY Cocktail Pool Building Guide and videos, in imperial and metric. Choose your size:

• 10ft x 7ft cocktail pool plans
• 12ft x 8ft cocktail pool plans
• 14ft x 7ft cocktail pool plans
• 14ft x 10ft cocktail pool plans
• 15ft x 8ft cocktail pool plans
• 16ft x 9ft cocktail pool plans
• 20ft x 10ft cocktail pool plans

Adding an in-pool lounger? Concrete Lounger – The Ultimate Guide walks you through it.

If you want something truly custom, such as an odd-shaped garden or a spool with a separate hot tub, design it in the free Tub & Pool Designer Pro software. I can then turn it into architectural CAD and a 3D plumbing design. For a full hot tub and pool combination, there’s also the hot tub and pool combo design consultancy.

FAQs

What size is a cocktail pool?

There’s no official size, but most are about 10–16ft (3–5m) long, 6–10ft (2–3m) wide and 3½–4½ft (1.1–1.4m) deep, with benches or loungers and no deep end.

What’s the difference between a cocktail pool and a spool?

They’re very similar. A spool (“spa” plus “pool”) is a cocktail pool with hot tub features such as heating and jets, so it can run as a warm spa in winter and a cool pool in summer.

Can I heat a cocktail pool with a hot tub heater?

Only slowly. A 3kW spa heater would take over 40 hours to warm 11,000 litres by 10°C even with no heat loss. An air source heat pump or a gas heater is the practical choice, with a spa heater as an optional top-up.

Do I need a fence around a cocktail pool?

In most of the USA, yes. The usual requirement is a barrier at least 48in high with a self-closing, self-latching gate. In the UK there’s no legal requirement for a private pool, but a secure fence of at least 4ft and a lockable cover are strongly recommended.

Can I build a cocktail pool from concrete blocks?

Yes. Use a reinforced slab and hollow blocks with vertical rebar, core-filled with concrete, or ICF blocks. Then waterproof with render and a pool-rated membrane before tiling.

Planning a cocktail pool or spool? 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