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In a nutshell: Essential tips for using a Gardenvity wood-fired hot tub

Hot tub Essential tips

Here, in one place, we’ll quickly overview the main points and warnings you need to know when using a Gardenvity hot tub with a wood-burning heater. Use this guide as an extended table of contents to refer you to the right spot in our rich knowledge base.

Find the basic tips and links to more detailed articles and short guidelines on some main points related to

  1. Fire
  2. Water
  3. Cleaning and maintenance
  4. General and safety

1. How to heat your hot tub

Fire burning in a wood-fired heater, heating the water efficiently in 1-4 hours.

Heating the water to the bathing temperature (~39°C) should not take longer than 1-2 hours in summer and 3-4 hours in winter and only 1–1.5 hours in summer, 2–2.5 hours in winter in the 1-2 seater Gardenvity hot tub. If you follow the detailed instructions here, you will easily achieve this.

Use a combination of softwood (to start and build a fire more easily) and hardwood (for the main heating phase and to maintain the heat for a long time). When heating the water, burn medium-sized logs (split into halves or quarters). Larger logs will take longer to heat the water and produce more smoke.

Medium-sized hardwood logs for heating the water in the most efficient way.

Prepare firewood in advance. Have some finely chopped kindling and larger logs ready to maintain the heat.

Barkless, kiln-dried hardwood firewood produces less smoke and soot.

Clean the combustion chamber and empty the ash drawer before each use to facilitate combustion and a better draught.

We recommend cleaning the chimney after 15-20 uses.

Open or close the heater vent for additional control of the fire.

If the smoke comes out through the heater door and not through the chimney, read here about several reasons for this and related solutions.

Never use coal! Excessive heat can damage the heater and the hot tub itself. Also, do not use any flammable liquids.

Putting a faux-leather cover on a hot tub, which helps to reduce the heating time.

Put the faux leather cover on. It’s a game-changer at reducing the water heating time by as much as an hour in some cases! Otherwise, the water loses heat through the entire surface area, which is quite large.

Open the cover from time to time to stir the water with a paddle or switch on the air-jets and check the temperature.

If you overheat the water, stir it well (or switch on the air jets) and add some cold water.

NEVER start the fire if the water level has not reached 10-20cm below the top rim.

NEVER leave the fire unattended.

DO NOT start draining the water when the embers are still alive.

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2. Rules of thumb to keep the water clean

If you want to keep the water fresh for a longer time, you have to use a filter to remove debris and chemicals to kill the bacteria. Please read our article on how to ensure pristine water hygiene. Below is our summary with the main points.

Use domestic mains water and filter it daily.

It is best to use domestic mains water to guarantee the best results in terms of keeping your hot tub fresh and safe to bathe in. Run the water filter daily for 4-5 hours. Check the filter cartridge often to ensure better filtering results.
To decide if the filter cartridge needs replacement: if the dirt comes off after a good spray with a garden hose, you can reuse the cartridge. When you can’t wash away the dirt, replace the cartridge (Type A). As a standard, replace the cartridge every 2-3 weeks.
When a sand/fibre ball filter is used, clean the strainer every few days, wash the fibre balls at least once in 3 months and replace them every 2 years.
If you add the optional UV-C module to further improve the water hygiene in your Gardenvity Premium wood-fired hot tub, you will need to replace the UV lamp every 9,000 hours of operation (that’s roughly once in 5 years if used 4-5 hours daily with the operating water filter, as recommended).

Keep the water sanitised and at the correct pH level.

Check the water pH levels daily to keep the water hygienic and prevent corrosion of the metal parts. If the pH level goes out of the 7.0-7.6 range, the sanitiser chemicals will not work.
Add chlorine-free water treatment products. It would be best to get a starter kit first, which will include all the necessary chemicals, pH level measurer, etc.
With the installed filtering system and chlorine-free, oxygen-based sanitisers, you can leave the water in for a longer time (2-4 weeks).
In Gardenvity Premium hot tubs with a sand/fibre ball filter and a UV-C module, you can keep the clear water unchanged even longer for as long as a few months. Also, the Premium models with an acrylic liner can be used with chlorine products for water treatment.

Change the water frequently.

If you want to enjoy an utterly chemical-free bathing experience in your wood-fired hot tub, we recommend draining the water in 1-2 days after 1-2 uses and refilling.
If your hot tub gets used by different people every time, you should change the water after each use.


Do not use chlorine chemicals with most of Gardenvity hot tubs as they can cause damage to the hot tub parts. Only Gardenvity Premium hot tub models can be used with chlorine chemicals.

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3. How to clean and maintain different parts of the hot tub

More details on this part are, of course, available in the Gardenvity User Guide. Below are the points to help you keep the hot tub working and looking flawless for as long as possible.

Adding firewood to the wood-burning heater of a Gardenvity hot tub.

Keep the original looks of Thermowood parts.

Over time, the Thermowood surface will become greyish – as any natural wood does. If you wish to maintain the original appearance of the wooden parts of your hot tub, once a year, treat them with transparent weatherproof wood stain containing some brown pigment.

Do not clean the Thermowood surface with detergents and/or hard brushes as it may damage the material.

Be gentle when cleaning your hot tub.

Use only a soft cloth or a sponge to clean the hot tub parts. Water is sufficient to clean the stainless steel elements and the wooden parts, and you may use dish soap to clean the fibreglass or acrylic insert, if necessary.
Do not use any chlorine-based chemicals for cleaning the hot tub, as these may cause damage or discolouration. Only Gardenvity Premium hot tub models are perfectly safe to be used with chlorine products.

Never use sharp cleaning tools because you will damage the surface of the hot tub parts.

Drain the water completely in freezing temperatures.

Leave the water drain valve open in subzero temperatures. Switch the air jets on for a short while to ensure there’s no water in the system.
If you have a model with an external heater (Gardenvity 1-2 seater Ofuro and Original models), you also have to drain the water from the heater to make sure that there’s none of it left.

Clean the water heater and the chimney after 15-20 uses.

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4. More general and safety tips for a wood-fired hot tub owner

This last part includes some common-sense rules of using a wood-fired stove or electric appliances, such as remembering to slide the ash grate into the heater before use or turning off the LED and air massage systems when finished bathing. Also, inform the young hot tubbers that the unprotected area of the chimney may get dangerously hot.

Showing the protected part of a chimney and the section that gets dangerously hot.

Lastly, we have to add the red-colour emphasis to the warning points so that you do not damage any hot tub parts or injure yourself.

Do not run the water filter and avoid adding chemicals when the hot tub is occupied.

Do not run the air-jets and water filter when the tub is not filled with water.

Do not leave any water in the hot tub in freezing temperatures. It will damage its parts.

Your safety and enjoyment when using a Gardenvity wood-fired hot tub are our top priorities. Do come back to our website and find many answers to all the different questions you may have. Also, feel free to contact us if you need any advice on using your spa!

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