How to Build the Ultimate DIY Stock Tank Hot Tub (with Jets, Filter and Heater)

Last updated: September 2026

Thinking about turning a stock tank (or a horse trough, as we’d call it in the UK) into a hot tub? It’s one of the cheapest and quickest ways to get a proper soak in the garden or backyard, and it’s a lot less work than digging a hole and building a block or ICF tub like I did.

But a bare galvanised tank with a hose in it is really an outdoor bath. In this guide I’ll go through the pros and cons honestly, then show you how I’d build what I call the ultimate stock tank hot tub: jets, filtration, a skimmer and a proper electric heater, so it runs and feels like a real hot tub.

What is a stock tank hot tub?

A stock tank is a big galvanised steel tank used on farms to give cattle and horses drinking water. In the UK you’ll usually see them sold as water troughs or horse troughs by agricultural suppliers. They’re designed to hold water outdoors all year, so it’s no surprise people started converting them into hot tubs. You’ll hear them called “hillbilly hot tubs” or redneck hot tubs, and they’ve become hugely popular.

Behlen Country, one of the best-known US makers, lists its Farmstead round tanks in these sizes:

Tank	Approx. diameter x height	Capacity (brim full)	As a hot tub
6ft round	65–69in x 23.5in (1.7m x 60cm)	389 US gal (about 1,470 litres)	2–3 adults
8ft round	89–96in x 23.5in (2.4m x 60cm)	706 US gal (about 2,670 litres)	4–5 adults
10ft round	113–120in x 23.5in (3m x 60cm)	1,117 US gal (about 4,230 litres)	A small plunge pool rather than a hot tub

Two things jump out. First, they’re only about 2ft (60cm) deep, and you won’t fill them to the brim, so you’re sitting on the floor in roughly 18–20in (45–50cm) of water. Second, there are no seats. That’s fine for a lot of people, but it’s worth knowing before you buy. If you want to sit with your shoulders under the water, a wooden hot tub or a built tub is a better fit.

The problems with a basic stock tank hot tub

When I came across stock tank hot tubs, I’d been using my own DIY tub three or four times a week for nearly two years. So I sat down and listed the downsides of the basic version, which is just a tank, a hose and maybe a wood-fired or external heater:

• Slime and algae. Standing water goes green and slimy quickly, especially when it’s warm.
• No filtration, so the chemicals do all the work and it’s hard to keep the water safe.
• Rust. More on this below.
• Mosquitoes and insects. Depending on where you live, standing water will attract them.
• Slow to heat. With a wood-fired heater you light the fire and wait, so a “quick dip” after work doesn’t really happen.
• Comfort and no jets. Sitting bolt upright in a steel tank with no bubbles isn’t everyone’s idea of a hot tub. I’ll let you be the judge.

Stock tank vs a block or ICF built hot tub

The alternative is a tub built from concrete block (cinder block) or ICF, which is what I built and what most of my customers build. It takes longer and costs more, and there’s more to heat. But what you end up with rivals, and I’d argue beats, a shop-bought acrylic tub.

	Stock tank hot tub	Block or ICF hot tub
Build time	A few weekends	Weeks to months
Skills	Plumbing and careful hole cutting	Groundwork, concrete, waterproofing, tiling and plumbing
Depth and seating	About 2ft deep, sit on the floor	Around 900mm–1m (36–40in) of water, with proper seats
Lifespan	Limited by rust unless lined or coated	Decades if it’s built well
Heat loss	High, as steel conducts heat. It needs insulating	Low with ICF or insulated walls

If the stock tank’s shallow depth puts you off, have a look at my DIY in-ground hot tub build guide.

How to build the ultimate stock tank hot tub

In the interest of balance, I sat down with a couple of cold beers and asked myself a question. What if I designed a stock tank hot tub that fixed every one of those problems? It won’t be as cheap as a tank and a hose, but it’s still cheaper and quicker than a block tub. There’s no big hole to dig, and you don’t have to worry about whether the vessel holds water, because that’s its job.

The recipe is simple: use the stock tank as the shell, then add everything a real hot tub has. That means a pump, a filter, a spa pack (heater and controls), jets, two suction drains and a skimmer. Circulation and filtration deal with the standing water, the slime and the algae, and the spa pack deals with the heating.

Choosing the tank

• Size. An 8ft (2.4m) round tank is the sweet spot for a family. A 6ft (1.8m) tank suits two or three people. I drew my first design around a roughly 6ft tank with 16 jets and room for four, but give yourself more space if you can.
• Galvanised or poly? Galvanised steel is the classic look but will corrode eventually. Poly tanks won’t rust, but check the maker’s rating for water at 38–40°C (100–104°F) before you buy.

The parts you need

Some parts change compared with a concrete tub. The gunite jet bodies I’m so fond of on block builds are made to be set in concrete, so they’re no good here. Instead, you use jet bodies with a screw-on front and a gasket, which clamp through the tank wall. The parts list looks like this:

• Jets, with a mix of air and water, just like a full-size hot tub.
• Two suction drains, fitted low on the side wall, so if one is blocked (or someone sits on it) the pump can’t pull hard on it. That protects the pump and, more importantly, people. In the USA, drain covers must meet the ANSI/APSP/ICC-16 standard under the Virginia Graeme Baker Act.
• A skimmer, pump, filter, spa pack and blower. The spa pack controls the heater, filter cycles and pumps. It’s a clever bit of kit.
• Pipe: 1in to the jets and 1.5in to the filter, with reducers at the pump.

That’s a screen grab of one of the plumbing layouts. My Ultimate Stock Tank Hot Tub DIY Guide has five different layouts (heating and filtration only, then 4, 8 and 16 jets, with and without a skimmer), each with its own bill of materials. If you’d rather not source it all yourself, the complete stock tank kits include the pump, spa pack, filter, blower, jets and drains. There are links to each one at the end of this post.

Cutting the holes and sealing the fittings

A good hole saw goes through the steel easily. Sealing the fittings is the hardest part of the build, because every hole you cut is a potential leak, so take your time.

1. Mark everything out first. Keep the jets at a sensible height for someone sitting on the floor, and keep the drains low. Hold each fitting in place and check it clears the tank’s ribs and corrugations. A gasket won’t seal across a ridge.
2. Cut the holes with a bi-metal hole saw at a slow speed. For the parts in my kits, the jets need a 65mm (2.56in) hole and the drains need 85mm (3.35in). If you’re using other parts, check their sizes.
3. Deburr and protect the cut edge. Cutting removes the zinc and leaves bare steel, which is exactly where rust starts. The American Galvanizers Association lists zinc-rich paint as an approved repair for bare areas. Brush it onto the clean, dry edge and let it cure before you fit anything.
4. Fit the jet bodies with a gasket on each side of the tank wall, then screw the front back on tightly to clamp the seal. For extra security, add a bead of a waterproof sealant or epoxy that bonds to both metal and plastic, and that is rated for continuous immersion.
5. Fit the drains. The drains I use have a sealing ring and a locking nut on the back, so tightening the nut makes the seal. If it weeps, add more sealant.
6. Fit the skimmer. Cut the hole to the skimmer’s throat, not its face. The face should sit flush against the steel, with the top of the skimmer level with the top of the tank. That puts your water line around the middle of the skimmer opening.

One of the joys of a stock tank is that all the plumbing is on the outside, where you can see it and get at it. If something weeps later, you can fix it. I’ve used plumber’s epoxy putty that sets under water on my own tub, to repair a corner that came loose.

How the plumbing works

Hot tub plumbing falls into two halves. There’s the suction side, which pulls water into the pump, and the pressure side, which pushes it back out.

Suction side

The two drains and the skimmer feed the suction side of the pump. The drains are teed together so that suction is shared between them, as I explained above.

Pressure side

From the pump, water goes through the filter, then through the spa pack, where it passes over the heating element. Then it goes out through the jets back into the tub. So the jets deliver both the massage and the heat.

The control room

The equipment set-up is the same tried and tested one I use on concrete builds: pump, filter, blower and spa pack. Here’s one we put together for a customer, using Balboa and Waterway parts. You can swap some parts for cheaper ones, but these are the brands I trust.

The two gate valves let you isolate the equipment, so you can change the filter or take a part out for service without draining the tank. Keep the equipment close to the tank and below the water line where you can, because most hot tub pumps aren’t self-priming. There’s more in Hot tub control room design considerations, and I also do a separate stock tank control room guide.

Making leak-free joints

If the pipework is done properly, it won’t leak and it won’t come apart, ever. Cut the pipe square, deburr it, and use the primer (USA) or cleaner (UK and Europe) that matches your cement. Put cement on both the pipe and the fitting, then push it fully home and hold it. And make every joint at the right angle. Forced joints leak, and I’ve got the scars to prove it. My step-by-step guide is How to make a PVC solvent weld joint.

How to stop a stock tank hot tub rusting

This is the question I get asked most. The galvanising is a zinc coating that corrodes sacrificially to protect the steel. According to the American Galvanizers Association, warmer water attacks zinc more, chlorides are the most aggressive ion to zinc, and soft water is more corrosive than hard water. Hot tub water ticks all three boxes, and you can’t run low sanitiser levels to spare the tank. So here’s what I’d do:

1. Protect every cut edge with zinc-rich paint, as above. This is where rust starts first.
2. Keep the water balanced. Aim for pH 7.2–7.6 and total alkalinity 80–120 ppm, and keep the calcium hardness in range rather than running very soft water. Zinc corrodes fastest when the pH drops out of range. See my hot tub chemical levels guide.
3. Keep sanitiser levels right, but don’t overdo it. Chlorine at 3–5 ppm or bromine at 4–6 ppm. Never let tablets or granules sit against the steel. Dose through the skimmer basket or a dispenser that can’t touch the walls.
4. Don’t use a salt system. A salt chlorinator means a permanently high level of chloride in the water, which is bad news for zinc. There’s more on this in Saltwater in a hot tub.
5. Consider a liner or coating from day one. The only way to fully stop corrosion is to keep the water off the steel with a fitted liner or an immersion-grade coating. Plan it around the jets, drains and skimmer, and follow the product maker’s instructions.
6. Keep the outside dry and check the base and seams every few months for white powdery zinc or red rust spots.

Heating, insulation and running costs

The spa pack in my kits is a 4kW Balboa for the USA, and 3kW for the UK and Europe. Here’s roughly how long it takes to heat the water from cold, based purely on the physics. It’s a best case, because in real life the tank loses heat while it warms up, which is why the cover and insulation matter so much.

Tank (filled to about 20in / 50cm)	Energy to heat by 25°C (45°F)	3kW heater	4kW heater
6ft round, about 1,250 litres (330 US gal)	About 36kWh	About 12 hours	About 9 hours
8ft round, about 2,270 litres (600 US gal)	About 66kWh	About 22 hours	About 17 hours

Once it’s up to temperature, the heater only has to replace what’s lost, and that’s where insulation comes in:

• Get a cover. Most heat is lost from the surface. I’d buy an inexpensive round cover online rather than make one. A few hundred dollars (or pounds) should do it. See my guide to hot tub covers.
• Insulate the sides and the base. Steel conducts heat very well. Box the tank in with timber cladding and fill the gap with rigid board or closed-cell spray foam (much like a shop-bought acrylic tub), stand it on rigid insulation board, and insulate the exposed pipework.
• Beware of vermin. Warm, dry spaces full of fluffy insulation make lovely homes for our little four-legged friends. Rigid board or foam in a well-sealed cladding is far less inviting.

There’s more on this in DIY hot tub insulation. If you want to run it more cheaply, a small air source heat pump can do most of the heating, with the spa pack’s heater as back-up. See The ultimate guide to air source heat pumps for hot tubs.

Electrics and safety

You’re putting a heater, pumps and a blower next to a metal tank full of water, so this isn’t the place to cut corners.

• UK: A hot tub needs its own circuit with RCD protection, and a new circuit is notifiable work under Part P. Use a registered electrician, who will also check whether the tank and any nearby metalwork need supplementary bonding.
• USA: Spas and hot tubs come under NEC Article 680, and that includes the bonding rules in 680.26, which cover metal parts. With a steel tank, bonding matters. You’ll also need GFCI protection and a disconnect in sight of the tub. Get an electrician and check your local permit rules.

For the details, read A guide to hot tub electrics and Ground bonding a hot tub.

The base and landscaping

An 8ft tank holds around 2.5 tonnes (about 5,500lb) of water before anyone gets in, so it needs a solid, level base. A concrete pad or well-compacted gravel is ideal. Don’t put it on a deck unless the deck is designed for the load, and don’t put it on grass. My guide to building a hot tub base covers it.

After that, the finish is up to you. Leave the raw, rustic look, box it in with a timber surround (which hides the insulation and plumbing), build a deck up to the rim, or landscape around it with big rocks so it looks like a rock pool.

For inspiration, see Ben’s stock tank kit build for his Airbnb.

Common mistakes

• Buying the tank before you’ve checked the jets, drains and skimmer will fit between its ribs.
• Leaving cut edges bare, so rust starts at every hole.
• Only fitting one suction drain.
• Letting chlorine tablets sit against the steel, or using a salt system.
• Putting the equipment above the water line, so the pump won’t prime.
• Skipping the cover and insulation, then wondering why the heater never switches off.
• DIY electrics. Please don’t.

Planning your own stock tank hot tub?

If you want to do it all yourself, start with my Ultimate Stock Tank Hot Tub DIY Guide. It has five plumbing layouts with a bill of materials for each, plus hole-cutting and assembly steps. Add the stock tank control room guide if you’re building an enclosure for the equipment.

If you’d rather have the parts in one box, the complete stock tank kits include the pump, Balboa spa pack, 25 sq ft filter, fittings and a DIY guide. You just add the tank and the pipe:

• Heating and filtration only (no jets)
• 4-jet kit
• 8-jet kit
• 16-jet kit

Want some help with the parts or the design? Pop your details in below and tell me what you’re planning.

FAQs

How much does a stock tank hot tub cost?

For a proper stock tank hot tub, budget for the tank, a plumbing kit (from $1,399 for heating and filtration only in my shop), pipe, a cover, insulation and the electrician. That’s still well below a block-built tub.

Can you put jets in a stock tank?

Yes. Use jet bodies that clamp through the wall with a gasket on each side, rather than gunite jets. Seal them with an immersion-rated sealant, and protect the cut edge of the steel with zinc-rich paint first.

Will a galvanised stock tank rust as a hot tub?

Eventually, yes, unless the water is kept off the steel. Warm, sanitised water wears away the zinc faster than cold drinking water does. Balanced water, no salt system, protected cut edges and a liner or immersion-grade coating all make it last much longer.

How deep is a stock tank hot tub?

Most round tanks are about 2ft (60cm) tall, so you’ll have roughly 18–20in (45–50cm) of water and you sit on the floor. There are no built-in seats.

Can I use chlorine in a stock tank hot tub?

Yes. You need a sanitiser to keep the water safe. Keep it in the normal hot tub range, dose through the skimmer or a dispenser (never tablets sitting on the steel), and keep the pH at 7.2–7.6.

Is a horse trough hot tub the same thing?

Yes. “Horse trough” is what we tend to call a stock tank in the UK. Everything in this guide applies, but check the size and depth before you buy, because UK troughs come in lots of shapes.

Got a question about your own stock tank build? Drop it in the comments below. I read them all.

Cheers,
Andi

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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