Singema – Wood Fired Hot Tub Coil Manufacturer & Supplier
Stainless Steel Wood Fired Hot Tub Coil Manufacturer | Outdoor Spa Heating Parts
Advantages of Wood Burning Outdoor Spa with Stainless Steel Heat Exchange Coil
Our custom stainless steel heating components for SPA tub bring multiple unique benefits to off-grid backyard wooden hot tubs and DIY stock tank heating systems, delivering energy-saving, low-cost outdoor bathing without electricity support. Crafted from anti-corrosion stainless steel, these heat exchange coils speed up water heating and work entirely off-grid with no electricity, outlets or wiring needed, running only on natural firewood for cabins, glamping sites and wild backyard builds.
This power-free design slashes your monthly spa utility costs, cutting long-term operation and maintenance spending by replacing pricey electric heating with affordable local firewood. It unlocks unlimited placement freedom to set your soaking tub in forests, lakesides or remote land with no grid restrictions, while creating gentle, chemical-free hot water perfect for family outdoor bonding and camping trips. Matched with insulated cedar hot tubs, our heating components deliver consistent warm soaks all year round, even in freezing winter frost and snow, and support multi-person group soaking with a safe separated external heating structure. Our heating solutions also work seamlessly with stylish portable soaking tubs, letting you move your spa across yards and mountain properties without permanent plumbing or electrical installations.
Premium Stainless Steel Wood Fire Heater Coils
No Power Required – Fully Wood-Fired Operation
Save Thousands On Monthly Spa Utility Bills
Unlimited Off-Grid Placement In Natural Wilderness
Wood-Fired Hot Tubs For Family Camping & Glamping
Insulated Cedar Wood Hot Tubs For All-Season Use
Multi-Person Cedar Hot Tubs With External Wood Stoves
Portable Designer Wood-Fired Soaking Bathtubs
How a Wood Fired Hot Tub Coil Works
A wood fired hot tub coil is a stainless steel heat exchanger that warms your tub water using nothing but firewood. Cold water from the tub enters the bottom of the coil, absorbs heat from the flames licking the coil’s outer surface, rises as it heats, and flows back into the tub through the top outlet. This continuous thermosiphon loop circulates water naturally, with no pump, no electricity, and no moving parts.
The result is a heating system that runs entirely off-grid. Light a fire in the firebox beneath the coil, and within 1 to 3 hours (depending on tub size, water volume, and fire intensity) you have a hot soak ready anywhere you can place a tub. The same principle heats stock tanks, cedar barrel tubs, portable soaking tubs, and small swimming pools.
Every Singema coil is built from corrosion-resistant stainless steel rather than the copper or galvanized steel some DIY builds use. Stainless steel holds its shape under repeated heating cycles, resists pitting from mineral-rich or chlorinated water, and lasts for years of regular winter use without the thinning or green oxidation copper develops over time.
Choosing the Right Wood Fired Hot Tub Coil Kit
Matching the coil to your tub is the single biggest factor in how fast your water heats and how long the system lasts. The wrong size means slow heating, wasted firewood, or a coil that cannot keep up on cold nights.
Tub size and water volume. A 200-gallon stock tank needs a different coil than a 500-gallon cedar barrel. Undersized coils struggle to reach soaking temperature in reasonable time. Oversized coils heat fast but cost more and burn more wood than the tub needs. Our coil kits are sized across model tiers (A through F) to match common tub volumes from single-person portable tubs up to multi-person group tubs.
Placement: internal vs external coil. Internal coils sit inside the tub and heat water directly. External coils (with a firebox outside the tub wall, connected by hoses) keep the fire separated from bathers, which is safer for families and groups and lets you tend the fire without getting out of the water. The Model C2 off-grid coil kit with legs, wood holder, ash pan, and hose set is our most popular external configuration for backyard and cabin builds.
Accessories that change the experience. A wind and smoke shield around the firebox cuts heat loss on breezy days and keeps smoke out of your face. A ground support stand lifts the firebox off wet ground. An ash collector makes cleanup fast. A BBQ grille turns your heater into a cooker while the tub warms. These are bundled into the higher model tiers (C, D, F) so you buy a complete kit rather than sourcing parts separately.
Your tub type. If you are heating a stock tank, a basic A-series coil kit is usually enough. For a cedar barrel hot tub, an external C or D series kit with support stand gives you the safer, cleaner setup. For a portable tub you move between properties, look at the portable wood fired hot tub options that pair a lightweight tub with a matched coil.
For a full walkthrough of coil materials, sizing math, and model-by-model comparison, our guide to choosing the right wood fired hot tub heater coil breaks down every factor in detail.
Stainless Steel vs Copper Coils for Hot Tubs
Searches for “copper coil hot tub” and “copper pipe for portable wood fired hot tub” come up often, so this is worth addressing directly. Both metals work as heat exchangers, but they behave differently over years of use.
Copper transfers heat slightly faster than stainless steel, which is why many DIY builds use copper pipe. The tradeoff is durability. Copper softens and thins with repeated heat cycling, develops green oxidation (verdigris) that flakes into the water, and is vulnerable to corrosion if your water is acidic, chlorinated, or mineral-heavy. Copper coils in outdoor tubs typically need replacement within a few seasons.
Stainless steel heats marginally slower but holds up far longer. It resists corrosion from chlorinated, salty, and mineral-rich water, holds its structural shape under years of heating cycles, and does not leach into the soak water. A stainless coil is the choice when you want a heater that lasts decades rather than seasons, which is why every coil Singema manufactures is stainless.
If you already own a copper coil and want to understand the upgrade path, the same coil selection guide covers material tradeoffs in depth.
Off-Grid and Winter Heating
A wood fired coil heater is one of the few hot tub heating methods that works with zero electrical infrastructure, which is why it shows up in off-grid cabin, glamping, hunting camp, and remote property builds. You need a tub, a coil kit, firewood, and water. No outlet, no wiring, no electrician.
In winter, the combination of an insulated cedar barrel tub and a high-output stainless coil keeps water at soaking temperature even in below-freezing air. The external firebox design means the fire stays outside the tub wall, so snow and ash never enter your soak. Our tips for using your wood fired hot tub cover cold-weather firing technique, wood choice, and how to protect the coil when the tub sits unused in freezing weather.
Building vs Buying: What to Expect
If you are weighing a DIY build against a complete kit, the tradeoff is time and reliability. A DIY copper-pipe coil can work, but sourcing the right gauge pipe, bending it without kinking, welding fittings, and building a safe firebox takes tools and experience. A complete kit gives you a matched coil, firebox, hoses, fittings, and support hardware engineered to work together, with the stainless construction that lasts.
For builders who want to assemble the full tub-and-heater system themselves, our step-by-step guide to building a wood fired hot tub with a heater coil kit walks through the full process. If you already have a traditional electric or gas tub and want to convert it to wood-fired, the tub conversion guide covers what to change and what to keep.
Frequently Asked Questions
How long does it take to heat a wood fired hot tub?
Typically 1 to 3 hours from cold to soaking temperature (around 100 to 104°F / 38 to 40°C), depending on tub volume, water starting temperature, fire intensity, and whether the tub is insulated. A 200-gallon stock tank with a properly sized coil usually hits temperature in 90 minutes with a good fire.
Do I need electricity or a pump?
No. The coil circulates water through natural thermosiphon (hot water rises, cold water sinks), so the system runs entirely on firewood. No pump, no outlet, no wiring.
Can I use a wood fired coil with a stock tank?
Yes. Stock tanks (galvanized or poly) are one of the most common tubs paired with our coils. The full product range includes kits sized for standard stock tank volumes.
Will the coil work in winter?
Yes. Stainless steel coils hold up in freezing conditions, and an insulated cedar tub retains heat well in cold air. The main winter consideration is draining the coil if the tub will sit unused for days in hard freeze, to prevent ice expansion damage. See our tips page for cold-weather firing and storage.
What is the difference between the model tiers (A, B, C, D, F)?
The tiers increase in features and accessories. A-series are basic coil kits for simple stock tank setups. C and D series add external fireboxes, support stands, ash collectors, wind shields, and BBQ grilles for safer, cleaner, more complete backyard builds. F series covers portable tub and coil combinations. Browse the products page to compare models directly.
Do you ship internationally?
Yes. Singema ships to the USA, Canada, UK, EU, Australia, and Japan. Contact us at sale@singema.com for shipping quotes and OEM/wholesale inquiries.
Where can I get help choosing or installing?
The FAQ page covers common shopping and warranty questions. For model selection advice or installation help, email sale@singema.com or reach us via WeChat at 0086 13586902090.