Is it the simplicity of heating an electric-free hot tub with timber as the wording ‘Wood-Fired Hot Tubs‘ suggests, or do you automatically think of custom-built wooden hot tubs, or perhaps, on the other hand, you’ve had thoughts of building one of your own design out of wood?
Maybe you’re the nostalgic type who fancies the ‘old-fashioned’ hot tub made completely of timber, but how on earth do you go about heating it?
Many concepts have been introduced using in-built heaters with wood, oil, gas or electricity to provide the heat through different adaptations of the basic design, but it’s a minefield with the different options available.
Maybe you’ve already looked on Amazon to check electric-free hot tubs or wood hot tub reviews, but you find very little shown.
Sadly it’s all down to their keyword search engine algorithms, which fail big-time with wooden hot tubs, so here on Lazeetimes we’ll try to make some sense of it all for you and show some examples of what we’ve found.
Wood-Fired Hot Tubs
Wood Fired Hot Tubs using externally heated tubing over a fire
Wood Fired Hot Tubs having their own standalone external hot tub heater
Wood Fired Hot Tubs with a built-in heater
All-Wood Hot Tubs
All-Wood Hot Tubs – electrically heated
All-Wood Hot Tubs – gas heated
All-Wood Hot Tubs – timber, coal or coke heated
It must be understood that if you are using oil, coal, timber or gas to heat a hot tub, there is no way you can have a hot tub with bubbles or jets as these need an electric source to provide the current and bubbles.
Not only that, but temperature control can be a bit hit and miss until you have experience with your hot tub and regulating the fire itself.
Regarding sanitization, you can use water straight from your tap and simply heat it up – no chemicals need to be added, especially if the timber is cedar, so that keeps your costs lower.
Just drain when the water looks a bit iffy, and the water can be used anywhere in your garden as there are no harmful chemicals involved.
One of the main beauties of a timber hot tub is the fact you’ll need very little insulation as the timber itself has wonderful thermal insulation. Providing you have a good cover over the top, you’ll lose very little heat unless you live in the middle of the Arctic Circle.
This means you may not have a suitable sealing cover over the top to retain the heat, but it can be done using a cover over just the water itself.
So, let’s get back to wood-fired hot tubs…
Wood-fired hot tubs come in many shapes and forms, but for heating purposes, the simplest versions have a basic stainless steel coiled tube surrounding a fire – can be wood, coal or coke, even barbeque coals, providing the heat for your water.
These are generally used where the fuel, wood, is plentiful, much like the water they are heating, even sea water.
Because of this, they require none of the usual chemicals to be added before use.
They require zero electricity and obviously they do not provide bubbles or any sort of current for jets, as they are simply using the thermosyphon method of heating.
Hot water rises to the top of the hot tub while the cooler water sinks and returns to the lower levels and into the heater source, so obviously you will need some sort of stirring device to spread the heat evenly, and it is always wise to do this before you get in.
If you have access to a power source, you can add a pump or bubbler to the system, or alternatively with a cavitation tube after the heated side of the piping before the pump to provide the bubbles, but more than likely this will not be sufficient to give the volume of bubbles you need.
One point is, if you want to go down this route, you need to make sure the top of the cavitation tube sits above the water level in your hot tub, otherwise the water will siphon out of your hot tub.
This, in effect, means the top of the hot tub is hotter than the lower layers of water and this all depends on the diameter of the pipe being used in the thermosiphon.
Usually, a one-inch pipe is sufficient to promote free-flow in a 300-gallon hot tub, so that layering is not pronounced in the column of hot tub water, but this is dependant on the volume of your hot tub as the larger the volume, the more pronounced the layering becomes.
Greater volumes require a larger diameter pipe to provide efficient flow which in turn means a larger fire must be used.
Wood-fired hot tubs, other than the simple stainless tube varieties, also come with an external boiler generally offering a 3 to 4-hour warm-up time, using its own flue to promote the draft through the fire and these are much more controllable for hot tub temperatures, despite the fact they are a little more inconvenient for the occupants.
The heated flue draws air through the fire, which in turn makes the water hotter, so the only way to restrict the heat is to reduce the air-flow, which is quite a simple process of sliding a damper over the air induction hole at the base of the fire, or, as in the case of the heater above, to simply adjust the opening of the bottom flap to get the air-flow right, but that means someone has to step out of the hot tub to complete the task if the temperature starts to vary.
They will not provide enough flow to create bubbles in any shape or form without adding electricity and forced flow.
Just to give you some idea, these come ready pre-cut and do not require complicated skills to produce this fantastic hot tub. Anyone with a reasonable woodworking ability from basic schooling should be capable of producing their own hot tub.
Also included is the complete boiler and tooling. All you need is water and wood.
Gas Fired Hot Tubs
These work on the same principle, but they do not need the suction created by the hot flue gasses rising to draw air through the fire. Having the draw through the fire means the gas will be at a lower pressure, meaning it needs enrichening to burn properly, so the control is usually isolated from the flow of exhaust gas up the chimney.
Instead, they require the gas volume increasing or restricting to control the flame and heat provided, meaning someone, again, needs to climb out to control the heat if it is not done electrically.
This one is the only completely wooden hot tub we have found so far using gas heating as a heat source, despite the fact it is provided as a DIY guide, but there are bound to be more and we will update as we find them.
Electrically Heated Hot Tubs
Now, these hot tubs are all fundamentally the same build structure, but with an electricity supply, that brings us all the bells and whistles you associate with any commercial hot tub you may wish to buy.
You can have the benefits of a ‘true’ hot tub appearance, rather than synthetic materials like fiber-glass, acrylics or plastics, but you can have far easier control of temperature and flow and it becomes a lot easier regarding maintenance, as there are no ashes to clear away or fires to light.
Mood lighting, music, massages, wine chillers, heated towel rails during the cooler evenings and many other additions like ozone bacteria killers or whatever may take a fancy – you can have the lot.
In fact, you can jump in straight away rather than having to wait for the water to heat up each time if the temperature is down a little.
Self Assembly Wood Fired Hot Tubs
Maybe you are looking for a wood DIY Hot Tub Kit?
In the US we have just two options so far that we have found…
- A self-assembly kit to produce a timber wood-fired hot tub
- A set of plans to produce your own hot tub from scratch (gas-fired)
Looking for complementary self-assembly all-wood saunas?
Canadian Redwood Cedar Saunas are provided by MCP Distributions through Amazon and come in two sizes.
Both are barrel-shaped with strong stainless steel bands holding the shaped wood together, so can be adjusted if needed and both have stands to keep them off the ground.
Noticed the molded shaping on the edges of the timber? A great way to make sure there are no air gaps for cold drafts.
They are electrically heated with an internal wet or dry heater using lava rocks and are provided with a water bucket and ladle to create the steam.
At first glance, two of them look identical, but there are two sizes to choose from.
A further one from the same supplier – self-assembly again in Canadian Red Cedar, is a 6kw version at 6 ft diameter and 6 ft long, but this time with a shingled roof, just to be a little different.
However, in the UK they have taken this process to heart – more can be found on our