Simplicity Of A Wood Fired Hot Tub: How Does It Work [September 2020]


We usually talk about expensive electric hot tub options that many of us were not aware of wood fired hot tub options. In this article, I am answering common questions about these beautiful, all-natural and affordable hot tubs.

A short answer to how does wood fired hot tub work would be the following:

The warmth you experience inside the tub comes with fire so we can say that in most cases a wood-fired hot tub heater is necessary unless you use an electric one. Gravity is a major key since it makes the warm water flow upwards while cold one gets down. This cyclic water movement is constant when using a wood-fired hot tub. 

Obviously, there more to it than just circulation of warm and cold water and picking the right stove. Let’s dive a bit deeper into the topic and answer some interesting questions.

How To Use A Wood Fired Hot Tub

A wood-fired hot tub reminds of the days before electricity or access to natural gas. Many hot tub purists like the natural experience of soaking in a hot tub that is heated by burning wood. If you like it, it is still very possible to purchase this type of spa from several manufacturers.

Using a wood-fired spa requires a little more work than using electric or gas heaters, but the basic principles are the same. I have to say that it is a healthy replacement of the hot tubs that we have used to seeing around, and you will see why.

The water from the tub tank flows through the heater, then through a filter system and back into the spa.

The main difference (from a hot water point of view) is that a wood-fired spa boiler cannot keep the water in your spa at a certain temperature as the other heating options can. In addition, the heat tends to stratify, meaning that hotter water rises while the cooler water sinks. To prevent this, use a paddle or similar device to stir the water occasionally while soaking.

The basic operation of a wood-fired hot tub focuses on the heater and maintains the correct water level to cool the heater and the airflow. If you light a fire in the heater, it is best to use clean fire paper for the initial ignition, followed by a dry light covered with crossed stems. The rule of thumb is simple: the more wood you use, the faster the water in your hot tub reaches hot temperatures (about 104F). The more wood you add, the longer the water stays at the right temperature. If the water gets too hot, moisten the fire and reduce the airflow into the stove, which will cool it down pretty quickly.

Make sure that the outside of the wood heater is sufficiently cooled. This often means water cooling, which needs to be monitored to maintain it. Some stoves are made of metal (e.g. aluminum) which melts if you do not monitor the cooling system.

Canadian Redwood Cedar 5 Outdoor hot tub – Perfect for cold days

Smoke is the other potential problem with a woodburning spa radiator. The use of high heat and low smoke fuel sources helps to reduce smoke pollution, as does ensure that the wood is very dry and not green. Keep the stove chimney (if present) clean (Amazon link) and free of obstructions. This is very important!

Are Wood Fired Hot Tubs Any Good

First of all, a wood-burning wooden hot tub does not need electricity. You only burn wood to heat it, and a wood-fired wooden hot tub has many advantages. The most important of all of them is that there is a lot of money being saved. Besides, you have the wonderful smell of a fire, combined with the relaxation in a beautiful hot bath! You relax and save money!

Bonus reading

How Long Should You Really Stay In Hot Tub?

I find it interesting that most people have no clue about how long they should soak in their hot tub. It’s not just the temperature that can hurt you, it’s also the water itself. I compiled some great information on this topic right in this article for you to read.

The chemicals that go through our hot tubs are terrible. Not only is there always more to put in when you use it, but there’s always a number on your hair and skin, unlike normal water which is exactly what a wooden spa uses. Simply normal water is all it takes.

Certainly, there is some more maintenance required, but just emptying and refilling, with some scrubbing and occasional soaping in between is what you do most of the time.

There was a case one guy had on a forum where after a while, one of the push buttons on his family’s spa controls broke. Apparently some moisture came. They knew that a new part to fix the problem cost over $500.

Today they still haven’t replaced it because half the nozzles are working, so is the lighting, and the temperature control is good too. With a wooden hot tub we wouldn’t have to worry about slightly defective or damaged electrical parts, nor would we have to worry about the expensive replacement. You just heat it up with wood and clean it when you are done. Fast, easy and without expensive parts!

The real advantages of a wooden hot tub are its simplicity. Most people get a hot tub to relax and unwind, and you should certainly be able to! A wooden hot tub allows you to do just that!

How To Build A Homemade Wood-Fired Hot Tub With 6 Elements

For someone who has experience in building things around the house, it can be relatively easy to put up a simple homemade wood-fired hot tub. You will need 6 basic elements that can be purchased in Home Depo. So let’s start.

  1. Quikrete Fast Setting Concrete Mix
  2. Quikrete Gravel
  3. Modern 169 Gallon Stock Tank
  4. Modern Push-To-Connect Fittings
  5. Modern Through Wall Pipe Fitting
  6. Modern Copper Tubing

Now here are the proper steps to take in order to do this:

Place the stock tank

I placed the 169 gallon stock tank on the ground where I wanted my wood-fired hot tub to be and then traced the perimeter of the tank in the dirt. After that, I dug about 8 inches into the ground.

(If you would like to get a DIY-ready wood hot tub, please check the product below)

Pour the foundation

I don’t want the filled tank to sink into the ground so used Quikrete Fast Setting mix to make a pair of quick and easy foundation slabs.

Make the heating coil

I cut a 20-foot long piece of ½” copper tubing and bent it in a coil around a 5-gallon bucket. I wanted the coil to be about 18 inches tall from top to bottom.

Make supports for the wood-burning hot tub coil

I cut some 1” by 1/4” steel bars to make supports for the coil. I drilled holes in the bars so that I could bolt them together around the copper tubing.

Drill holes in the stock tank 

I used a hole saw to drill 1-3/8” diameter holes 18 inches apart in the stock tank.

Add the fittings

I threaded the tank fittings through the holes and sealed them with silicone caulk. I screwed the push-to-connect fittings into the through-wall fittings.

Plug in the copper

The ends of the heating coil were a bit bent so I trimmed them before inserting them into the fittings.

Secure the wood burning hot tub coil 

I pounded the steel bars into the ground and added a second set to make sure the coil was sure.

Build the coil
I used ¾” redwood to make a lid that fits over the tank.

Test
It was 63 degrees outside and the water started at 56 degrees. It took about 2 big armfuls of firewood and 2 hours to heat the water to 110 degrees.

Do Wood Fired Hot Tubs Bubble

Originally, they don’t. However, there is an equipment that you can get for about $90 that will have a motorized air pump. I found this product on amazon and will leave a link in case you decide to check out. 

  • MASSAGING BUBBLES: This mat instantly creates a soothing bath spa. All you need to do is to place the mat in the tub, sit back and relax! It is designed to lay on your bathtub floor. It includes a connected air hose that delivers massaging bubbles
Sale
Electric Bathtub Bubble Massage Mat - Waterproof Tub Massaging Spa, Full Body Bubbling Bath Thermal Massager Machine w/ Heat, Motorized Air Pump, Aroma Clip for Essential Oil - SereneLife PHSPAMT24HT
  • MASSAGING BUBBLES: The SereneLife Bath Massage Mat instantly creates a soothing bath spa. Just place the mat in the tub, sit back and relax! Designed to lay on your bathtub floor. Features a connected air hose that delivers massaging bubbles
  • MOTORIZED AIR PUMP: Equipped w/ a motorized air pump responsible for producing millions of air bubbles every second. It is to be placed outside your bathtub with distance. Features automatic safety power-off function. Includes 8.2 ft air hose
  • BUILT-IN HEATER: Features a built-in heater that creates a soothing and warming experience. Works when the appliance is switched on and is not designed to heat up a cold bath but maintaining the water temperature w/ warm air created by the main unit
  • SUCTION CUPS: Mat is soft, fully submersible and 100% waterproof. It is also mold-resistant, cushioned and has a padded surface. Measures 47” x 14.2” offering full body support and comfort. Equipped w/ suction cups under the mat for non-slip comfort
  • REMOTE CONTROL: Allows you to adjust bubble intensity using the included remote for a hassle-free operation. Package includes a power cable and aroma clip to incorporate essential oils into your bubble bath for a more relaxing and soothing experience
  • MOTORIZED AIR PUMP: It comes equipped with a motorized air pump that’s responsible for producing millions of air bubbles every second. Which seems like a lot. It is intended to be placed outside your bathtub with distance. It includes automatic safety power-off function and 8.2 ft air hose
Intex Quick-Fill AC Electric Air Pump, 110-120V, Max. Air Flow 650 L/min
  • Plugs into any standard 110-120v wall outlet
  • Includes 3 interconnecting nOuncezles
  • Max air flow: 650 L/min
  • BUILT-IN HEATER: This one is really interesting as it includes a built-in heater that creates a soothing and warming experience. It works well when the appliance is switched on. It is important to know that it isn’t used to heat up a cold bath but rather  to maintain the water temperature with warm air created by the main unit
Sale
CalPalmy Immersion Heater | Submersible Water Heating with Stainless-Steel Guard and Thermostat | Heats 5 Gallons of Water in Minutes | Great for Bathtub,Inflatable Pool - (FULLY IMMERSED WHILE USING)
  • Twice the Power: Heat water faster with our 1800-watt water heater and within minutes the water (About 5 gallons) will be noticeably warmer. (Warning: - When heated, it is prohibited to put a hand in the water to test the temperature, one needs to always unplug first before touching the water - It is required to fully immerse the heater in water to avoid any potential fire hazard).
  • Rust Proof Stainless Steel Guard: The protective guard ensures no direct exposure to the heating element by people or pets. Heat dissipates to the water faster by flowing through the holes in the guard.
  • Easy to Use: Fully submerge the UL 499 Standard certified heater in a bucket, tub or trough of water and plug into a grounded 120v plug. You can submerge the handle and cord. Feel the difference in a few minutes!
  • Widely Application: The immersion water heater can be used in water, especially fit for heating water in large size container like bucket, basin, bath tub, mini inflatable swimming pool, etc.
  • For any Cold Weather Application: Heat your farm animals’ water, your tiling water on the job site, car wash bucket, pail of bath water in a tiny home or camper, window washing water and more! WARNING: Remove the heater before touching the water and please do not continuously use for over 4 hours!
  • SUCTION CUPS: Mat is extremely soft, fully submersible, and 100% waterproof. Many people will appreciate the next thing. It is also mold-resistant, cushioned, and has a padded surface. It goes 47” x 14.2” in size offering full-body support and comfort. It is equipped with suction cups under the mat for non-slip comfort
  • REMOTE CONTROL: It has an option of adjusting the bubble intensity using the included remote for easy operation. Power cable and aroma clip are both included in the package to incorporate essential oils into your bubble bath for a more relaxing and soothing experience

This could be a great addition to your homemade wood fired hot tub that will upgrade your regular hot tub into a somewhere luxurious version of it.

How Often Do You Need To Change Hot Tub Water

It will really depend on how often you use it and how many people you are sharing it with. In general, if we are talking about domestic use it is recommended to empty the water every 2-3 uses. However, if it is used by multiple people then it is best to change it daily. In case you would want to leave the water in for longer then it is recommended fitting a filtration system or using a sanitizing treatment.

How Much Are Wooden Hot Tubs

I analyzed Royal Tubs company that have wood fired hot tubs starting from $1900 for a model called Ofuro Hot Tubs, all the way up to $3800 for a model Fiberglass Deluxe Round Tubs that’s on sale right now. 

All of the oval wooden hot tubs come fully equipped with: 

  • Matching spruce or larch steps 
  • External heater and chimney components 
  • A practical drain 
  • The hot tub itself, which features two arched seats,  and stainless steel hoops

Find out more on their website since you can get several accessories that go nicely with these wood fired hot tubs and that are actually useful, such as:

  • Mini bar
  • Chimney Heat Guard
  • Stirring Paddle 
  • Air Bubble System
  • LED lights
  • Fiberglass lid
  • Internal heaters and more

Conclusion

I feel like I personally know more now then I knew before writing this article. In my personal opinion, just by going off these notes, it does seem like something that’s better for your health I guess since there is no need for heavy chemicals. Additionally, it has way fewer components and electrical parts which makes maintenance a breeze.

Going further down, there are options to buy or to make one yourself. Latter being a way cheaper option and works just fine. The only thing is that you have to control the temperature and make sure you don’t cook yourself in the tub. But you get used to it pretty quickly. 

I also noticed that there is quite a community behind these wood fired hot tubs, which means that you can seek and find a piece of advice pretty quickly. 

In the end, I think these hot tubs will last longer and are fully recyclable since it is made out of wood. 

Related Questions

Efficiency And Cost Of Wood Fire Heating Compared To Electric Heater

Heating the outdoor bathtub with wood is the traditional way, which requires no additional supply, only wood. We have three different types of wood heaters:

  • Internal
  • External
  • Integrated. 

As you can see, they are differently placed and connected, although the heating time is very similar. Of course, smaller tubs warm up faster, especially if you choose a stronger heater, while larger tubs need a bigger heater and a longer time to warm up. 

The efficiency of wood heating also depends on wood density. Therefore, hardwood is better than softwood because it has a density of 50% higher than softwood. 

It is important that no matter which wood you use for your wood stove, the wood must be dried. Wood that has not been dried wastes a lot of energy because it has to remove moisture from the logs when it burns.

The efficiency and cost of electric heating do not have so much inaccuracy because the energy used can be calculated accurately. Electric heating consumes 6 kW per hour, so you only need to know how many hours per day you have used it and the price of kWh in your country. 

Let’s say that the stove was on for 3 hours, so you used 18 kWh that day, multiply that by the cost of electricity per kWh and you have your price per day. 
How much does a wood stove cost in comparison? This is a tricky aspect, as it depends very much on the land, as well as the access to wood and its price. In addition, the amount of burnt wood cannot be measured accurately depending on the species, and it is also a little difficult to keep the temperature the same for a long time or not to overheat the water. It is therefore very likely that at least initially you will need more wood than necessary, while the electric radiator has a thermostat that allows you to set the temperature.

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Editorial Staff

I'm Adnan Sabanovic, the guy behind Hot Tubs Report. I've had a chance to enjoy hot tubs last few years and have really become interested in owning one of them. Nearly every weekend you'll find me spending time with my family or playing sports. If I am not doing that then I'm here writing about tubs on Hot Tubs Report. This blog is a research for my first hot tub which I decided to document and share publically so others can benefit from it as well.

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