Wood fired hot tub heater coil kit – All models
Price range: $1.00 through $428.00 Free shipping
Offer food-grade stainless steel wood-fired heater coils (A1-F4 models) transform barrels, tanks & pools into eco off-grid hot tubs with free shipping to US, EU, AU and more.
A wood fired hot tub heater coil kit turns almost any water container into a wood-burning spa without electricity or gas. Smartclima’s coil kits are built from food-grade stainless steel and ship in 24 standard models (A1 through F4), each designed to heat barrels, stock tanks, inflatable tubs, and small pools using nothing but firewood and natural water circulation. Free shipping is included to the United States, Canada, Australia, New Zealand, the EU, the UK, Ireland, and Japan.
TL;DR: The Smartclima wood fired hot tub heater coil kit is a food-grade stainless steel heat exchanger that converts barrels, stock tanks, and inflatable tubs into off-grid hot tubs. 24 standard models cover most container sizes, custom fabrication is available for non-standard builds, and free shipping reaches North America, Europe, Australasia, and Japan.
How a Wood Fired Hot Tub Heater Coil Works
The coil is a fire-powered heat exchanger. You build a wood fire inside or beneath the coil’s spiral, and water inside the tubing heats up. Hot water is lighter than cold water, so it rises out of the top of the coil and flows into your tub, while cooler water from the bottom of the tub is drawn into the coil to replace it. This continuous loop is called thermosiphon circulation. It needs no pump, no electricity, and no moving parts. As long as the fire burns, water keeps circulating and the tub gets warmer.
A typical 200-litre stock tank reaches 38 to 40 °C (100 to 104 °F) in 60 to 90 minutes depending on fire intensity, ambient temperature, and wind. Once you reach your target temperature, you let the fire burn down or add a rain deflector to protect the fire box while the coil keeps the water warm.
Product Information
| Specification | Detail |
|---|---|
| Product Name | Wood Fired Hot Tub Heater Coil Kit (All Models Series) |
| Brand | Smartclima |
| Primary Material | Food-grade stainless steel |
| Full Model Range | A1/A2/A3/A4, B1/B2/B3/B4, C1/C2/C3/C4, D1/D2/D3/D4, E1/E2/E3/E4, F1/F2/F3/F4 |
| Tubing Diameter | 25 mm |
| Coil Outer Diameter | 35 cm |
| Coil Height | 30 cm (±1–3 cm tolerance) |
| Spiral Circles | 8 |
| Core Function | Wood-burning water heat exchanger that transforms ordinary water containers into hot tubs |
| Optional Attachments | Height-adjustable BBQ grille kit, fire oven, second heater, carrying bag, rain deflector, rotatable dual BBQ grill kit, sealing cap for tub fitting |
| Shipping | Free to USA, Canada, Australia, NZ, EU, UK, Ireland, Japan. Inquiry required for other regions. |
Why Food-Grade Stainless Steel
The coil sits in hot water that touches your skin, so the material matters. Smartclima uses food-grade stainless steel that meets international drinking-water safety standards. This means no harmful metal leaching occurs during heating, even at high temperatures over many years of use. Food-grade stainless steel also resists corrosion from minerals, chlorine, salt, and acidic water far better than ordinary steel or galvanised alternatives.
For outdoor installations exposed to rain, snow, and freeze-thaw cycles, stainless steel is the practical choice. A coil left outside year-round in wet weather will not rust through the way carbon steel will, and it will not develop the pitting and scaling that shorten the life of cheaper alloys. With proper winter draining, the coil delivers a 20+ year outdoor service life.
Three Engineering Advantages
Seamless Extruded Stainless Tube
| Feature | Smartclima Use Seamless Pipe | Other Brand Use Welded Pipe |
|---|---|---|
| Manufacturing | No seams, one-piece extrusion | Welded from metal sheets |
| Strength & Pressure | Higher strength, better pressure resistance | Lower strength, limited pressure resistance |
| Wall Thickness | Uniform & consistent | Wall thickness may vary around the weld area |
| Appearance | No vertical seam lines, uniform inner surface texture | Obvious vertical weld line inside the pipe bore, uneven inner surface texture |
| Coils’ Service Life | Over 20 years of service life for outdoor applications | Shorter service life, prone to cracking |
| Leak & Rust Risk | Zero leakage during long-term continuous firing, anti-rust performance for outdoor environments | Weld joints are susceptible to rusting and leakage under long-term continuous firing |
| Freeze Resistance | Effective against ice bursting with stable performance | Welded pipes tend to crack under extremely low temperatures |
| Result | Premium-grade heater coil | Basic heater coil for low-demand scenarios |
Smartclima coils are made from extruded seamless tubing with uniform wall thickness. Seamless tube has no welded seam along its length, which means there is no weak point where pressure, freezing, or corrosion can start a leak. The even wall thickness distributes thermal and mechanical stress evenly, giving the coil higher pressure resistance and better freeze resistance than seamed tubing. The result is zero leak risk and zero rust risk over decades of outdoor use.
One-Piece Bent Full Coil (No Welded Joints)
Each coil is bent from a single continuous length of tubing. There are no connecting welds between spiral turns, which eliminates the joints that are the most common failure point on ordinary heater coils. Welded joints corrode first, crack under thermal cycling, and leak. By removing them entirely, Smartclima coils sustain reliable anti-corrosion performance for the full life of the product.
Premium High-Temperature Hose and Stainless Fittings
The hose that connects the coil to your tub is thick industrial silicone rated for sustained high temperatures. It will not melt, crack, or harden under extreme hot and cold weather, unlike plastic or regular rubber hoses that fail after one or two seasons. The tub connector fittings are stainless steel with tool-free quick clamps, so installation takes minutes and the fittings match the coil’s long service life rather than becoming the first part to replace.
Full Model Range: 24 Standard Sizes
The A through F series gives you 24 distinct coil models to match your container size, fire box dimensions, and heating-speed requirements. Each series (A, B, C, D, E, F) includes four variants (1, 2, 3, 4) that differ in coil dimensions and heating capacity. Whether you are heating a small 100-litre barrel or a large 500-litre stock tank, there is a model sized for the job.
All models share the same 25 mm tubing diameter, universal hose connectors, and food-grade stainless steel construction. The differences are in coil outer diameter, height, and the number of heating surfaces exposed to fire, which determines how fast the water heats.
If none of the 24 standard models fits your container or fire box, Smartclima offers full custom stainless steel tubing coil fabrication. Send your dimensions and requirements and we will build a coil to your specification.
What Is Included in the Kit
Each wood fired hot tub heater coil kit ships with:
- One food-grade stainless steel heater coil (your selected A1–F4 model)
- High-temperature industrial silicone hose
- Stainless steel tub connector fittings with tool-free quick clamps
- Sealing cap for the tub fitting
Optional add-ons available on this product page include a height-adjustable BBQ grille kit, a rotatable dual BBQ grill kit, a fire oven, a rain deflector, a second spare heater, and a carrying bag. You can also add a portable tub kit for one person or a portable tub kit for multiple people if you do not already have a container. For a complete turnkey setup, see our Dutch-style wood fired hot tub.
Installation Guide
- Choose your container. The kit fits wooden barrels, plastic stock tanks, small above-ground pools, inflatable hot tubs, and custom metal vessels. The container wall needs a hole large enough for the hose connector.
- Mount the coil. Position the coil so the fire box sits beneath or beside the coil spiral. The coil can be freestanding or mounted to a stand.
- Connect the hose. Attach the silicone hose from the coil’s top outlet to the upper fitting on your tub, and from the coil’s lower inlet to the lower fitting on your tub. Use the quick clamps to secure each connection. No tools are required.
- Fill the tub. Fill your container with water before lighting the fire. The coil and hoses must be full of water before heating begins.
- Light the fire. Build a wood fire in the fire box beneath the coil. Within minutes, water inside the coil begins to heat and circulate.
- Monitor the temperature. Check the water temperature periodically. A 200-litre tub typically reaches soaking temperature in 60 to 90 minutes.
- Maintain or extinguish. Add wood to maintain heat, or let the fire burn down to stop heating. The coil continues circulating warm water until the fire is out.
- Drain for winter. In cold months, drain the coil and hoses fully after each use to prevent freeze damage.
Application Scenarios
- Off-grid cabin and wilderness retreat soaking. No grid power is needed. Firewood heats the tub water, making the kit ideal for remote properties.
- Backyard DIY hot tub projects. Repurpose an old stock tank or wooden wine barrel instead of buying an expensive pre-built spa.
- Camping and glamping site amenities. The kit is portable and installs in minutes, making it practical for tourist sites that offer outdoor soaking.
- Homestead and self-sufficient living. Zero fossil fuel, zero electricity, and zero running cost beyond firewood.
- Custom outdoor landscape spa builds. Pair the coil with an inflatable portable tub or a custom-built vessel for seasonal backyard relaxation.
Custom Manufacturing and OEM
Smartclima operates its own manufacturing facility in Ningbo, China, with full capability in stainless steel tube bending, sheet metal fabrication, and custom coil design. Beyond the 24 standard models, we build custom coils to buyer specifications for non-standard containers, commercial spa installations, and OEM branding projects.
Custom options include:
- Non-standard coil diameters, heights, and tubing gauges
- Custom spiral turn counts for faster or slower heating
- Branded packaging and private-label labelling for resellers
- Bulk production runs for distributors and spa manufacturers
- Matching custom fire boxes, stands, and accessory kits
To request a custom quote, send your container dimensions, desired heating time, and target order quantity. We will provide a coil specification, pricing, and production timeline. See also our custom stainless steel tubing coil page for more on our fabrication capabilities.
Shipping and Regional Availability
Free standard shipping is included for orders delivered to the United States, Canada, Australia, New Zealand, EU member states, the United Kingdom, Ireland, and Japan. Orders to these regions typically ship within 1 to 2 business days and arrive in 3 to 5 business days.
Customers in other regions, including Scandinavia, the Middle East, Southeast Asia, and South America, should send a pre-order inquiry to confirm shipping rates and delivery timelines before placing an order.
The kit ships in a single package weighing 9 kg with dimensions of 50 × 40 × 30 cm, which keeps international shipping costs manageable even outside the free-shipping regions.
About Smartclima
Smartclima Co., Ltd. is a manufacturer and global supplier based in Ningbo, Zhejiang, China. Founded in 2001, the company has over 20 years of export experience and has served more than 10,000 customers worldwide. Our wood fired hot tub coil designs are patent-protected, and every coil is produced in our own facility under direct quality control rather than sourced from a third-party factory.
Our manufacturing capability spans stainless steel tube bending, sheet metal fabrication, cold forging, die-casting, plastic injection moulding, and rubber moulding. This means we control the full production process from raw tubing to finished kit, which is how we maintain consistent material quality, dimensional accuracy, and long-term durability across all 24 models.
We stand behind every coil with a 30-day return policy for orders shipped to the US, Canada, the UK, and Australia, with free return shipping by mail. If a coil arrives damaged or does not meet specification, contact us and we will replace it. Browse the full range in our wood fired tub coils category.
Frequently Asked Questions
How does a wood fired hot tub coil heater work?
A wood fired hot tub coil heater uses a natural thermosiphon process. You build a fire in the fire box beneath the stainless steel coil, which heats the water inside the coil. As the water warms, it rises through the coil and flows back into your tub, while cooler water from the tub is drawn into the bottom of the coil. This circulation continues naturally without any pump, electricity, or gas connection. It is a true off-grid heating method that works anywhere you have firewood and water.
How long does it take to heat a hot tub with a wood fired coil?
Heating time depends on your tub size, water volume, outside temperature, and how hot a fire you maintain. One customer reported bringing their stock tank to a perfect soaking temperature in just under 2 hours. Larger tubs or colder weather will take longer, but the coil’s large surface area and efficient heat transfer keep heating times competitive with electric heaters, without the energy cost.
What material are Singema’s heater coils made from?
Every Singema coil is built from 304 stainless steel seamless pipe, produced via one-piece extrusion with zero weld seams. This gives the coil superior structural strength, uniform wall thickness, and exceptional pressure resistance for both high and low temperature operation. Unlike the welded pipe most competitors use, seamless pipe will not leak, corrode, or crack at a weld seam even after years of continuous firing.
What is the difference between seamless pipe and welded pipe?
Seamless pipe is formed in one piece through extrusion, creating a pipe with no joints or weld lines. Welded pipe is made by rolling a flat sheet of metal and welding the seam shut. That weld is the weakest point in the pipe, prone to corrosion, fatigue, and cracking, especially in freezing temperatures. Seamless pipe has consistent wall thickness, higher pressure tolerance, and a 20+ year service life even under continuous heating. Singema uses seamless pipe exclusively for all coil kits.
Can I use the coil kit with my existing tub or stock tank?
Yes. Singema coil kits are designed to work with a wide range of containers, including galvanized stock tanks, wooden hot tubs, and even swimming pools. As long as your tub holds water and you can connect the inlet and outlet hoses, the thermosiphon system will circulate and heat it. If you are building from scratch, see our guide to https://www.singema.com/how-to-build-a-wood-fired-hot-tub-with-a-heater-coil-kit.html with a heater coil kit.
How long does assembly take?
Assembly is straightforward and requires no special tools. One customer reported connecting the hoses to their stock tank in about 15 minutes. The kit comes with everything you need to get started, including hoses and fittings. Always review our https://www.singema.com/safety-guidelines.html before your first fire.
Do the coil kits work in freezing weather?
Yes. The seamless 304 stainless steel pipe has exceptional anti-ice-burst performance and is highly reliable in extreme cold. Welded pipe is prone to cracking at the seam when water freezes inside it, but seamless pipe has no weak point to fail. The kits also include freeze protection features. This makes Singema coils suitable for year-round outdoor use, even in climates with hard freezes.
Which model should I choose?
Singema offers six model series, A through F, with multiple sizes in each. Models increase in coil length, heating capacity, and included accessories like BBQ grilles, fire holders, ash collectors, and wind shields. The right model depends on your tub size, how fast you want to heat, and which accessories matter to you. Our https://www.singema.com/how-to-choose-the-right-wood-fired-hot-tub-heater-coil-discover-the-affordable-and-eco-friendly-benefits-for-your-backyard-oasis.html walks through every model and helps you pick.
Do you ship internationally?
Yes. We offer free shipping to all countries and have exported coil kits to customers in the USA, Canada, Australia, Europe, and Japan. Our products are tested to perform in diverse climates, from freezing winters to humid summers. Browse all available https://www.singema.com/products/ in our store.
How long will the coil last?
The seamless 304 stainless steel construction is rated for 20+ years of reliable outdoor use, even under long-time continuous heating. Because there are no weld seams to corrode or fail, the coil maintains its structural integrity far longer than welded alternatives. With proper care and seasonal maintenance, a Singema coil is a one-time investment that can serve you for decades.
Ready to Transform Your Outdoor Retreat?
Whether you’re building a https://www.singema.com/how-to-build-a-wood-fired-hot-tub-with-a-heater-coil-kit.html , upgrading an existing setup, or creating a commercial outdoor spa, our Wood Fired Hot Tub Coil Kits offer the flexibility, durability, and efficiency you need. Choose your model, grab your wood, and dive into a warm, eco-friendly soak that connects you with nature, anytime, anywhere. Explore our https://www.singema.com/outdoor-soaking-tub-with-heater-c210518/ today, and review our https://www.singema.com/safety-guidelines.html before you fire up your first soak.
Additional information
| Weight | 9 kg |
|---|---|
| Dimensions | 50 × 40 × 30 cm |
| Purchasing option | Model A1, Model A2, Model A3, Model A4, Model B1, Model B2, Model B3, Model B4, Model C1, Model C2, Model C3, Model C4, Model D1, Model D2, Model D3, Model D4, Model E1, Model E2, Model E3, Model E4, Model F1, Model F2, Model F3, Model F4, B.B.Q Grill, Height adjustable BBQ Grille Kit, Rotatable Dual BBQ Grill Kit, Fire oven, Rain deflector, Second Heater, Carrying bag, Portable tub kit for single people, Portable tub kit for multiple people, Luxury Inflatable hot tub with heater coil, Sealing Cap For Tub Fitting |
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