While an electric heater usually means a convenient operation, a wood-fired heater offers many advantages.

Wood-fired hot tub means better operating costs, considerably quicker heating, and it’s a more sustainable option today that can be placed in your back garden, next to a woodland cabin holiday let, or just anywhere else you want. Let’s review the aspects that play important roles when deciding between a wood-fired and an electric heater for a spa to use at home. We’ll weigh in the pros & cons of both options.

1. Heating time – how long will it take to heat the water?

When it comes to water heating time, an average electric heater comes nowhere close to a wood-fired one, doing the job at least 6 times longer!

No less than four factors weigh in when it comes to water heating time, regardless of whether a wood-fired or electric heater is used. However, after keeping records for some time, we may talk about the average values, allowing you to get a general idea.

What determines the water heating time?

• The size of a hot tub
• Season – outside weather temperature
• Water temperature before heating
• Your experience

The average size hot tub needs 350 gallons (1,600 litres) of water.

A Gardenvity wood-fired hot tub with an integrated heater will take 1-2 hours to heat the water in summer and 3-4 hours in the cold season.

An electric heater will need 12-24 hours to heat the same amount of water, depending on the determining factors.

TIP: Covering the hot tub is crucial since uncovered water will lose heat through its all surface. Using an insulated cover may reduce the heating time by as much as a full hour!

With a wood-fired hot tub, your experience will factor in much more than with an electric heater (when you have close to no impact on the water heating time). Here are the tips for heating the water in the most effective way.

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2. Cost per single-use – how much will you pay to heat the water once?

A hot tub with an electric heater will, beyond a doubt, have a strong word on your electricity bills. The firewood needed for a wood-fired heater, on the other hand, may come from different sources and usually will cost substantially less than the electric power.

Heating the water requires 12-25kg of dry firewood. This may cost nothing if you bring any logs home after cleaning a park or a forest. Buying prepared kiln-dried hardwood logs of this amount may cost around £5-10 in the UK.

TIP: Use a mixture of softwood (to build up the fire) and hardwood (to maintain the heat), also different sizes of logs (smaller ones at the beginning and larger logs to retain the heat).

TIP: Kiln-dried, barkless firewood will produce less smoke and heat the water in the shortest time.

A standard electric heater will consume 6kWh of electricity every operating hour. Given the estimated electricity price in the UK of 34 pence per kWh*, a single heating will cost between £24-48.

*Based on the government Energy Price Guarantee rates from October, 2022 through to June, 2023.

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3. Sustainability – which type of heating is more eco-friendly?

The controlled amount of wood you’ll use in a wood-fired heater is an entirely renewable energy source.

In the UK, around 30% of the consumed electric power is generated from renewable supplies. The number keeps increasing, but it still leaves us with roughly 70% of the energy that puts a strain on the Earth.

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4. Convenience – a fire burning ritual vs a push of a button

Operating an electric heater offers the simplicity of a press of a button which might be a factor for some of us.

A wood-fired heater will make you do some prep-work, and you’ll have to take care of the ashes now and then.

It only takes plugging in and pushing a button with an electric heater.

You will incur costs for installing a suitable power outlet close to your hot tub.

You will be limited when choosing the spot for your hot tub.

You can install your hot tub anywhere you like. A classic model does not require any power, and the powered option needs only a basic 13Amp cable to supply energy over a reasonable distance.

You get to live out the sensations when preparing firewood and burning the fire – all by yourself or with the company.

Preparing the firewood will take time, as well as emptying the ash drawer occasionally.

You’ll have to get relevant information from the local authority regarding smoke-free areas in the UK to be able to use a wood-fired heater.

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5. The verdict – summing all up

The comparison in four key areas showed us more advantages of a wood-fired heater.

Forgive the bias, but the wood-fired heater is our bottom-line recommendation for wooden hot tubs.

Happy hot tubing!

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As fun as it gets heating the tub, you don’t want that process to take too long, though. 1-2 hours in summer, 3-4 hours in winter should do the job.

Even a perfect tub will not heat fast if you don’t follow some best practices. Below, you’ll find our tried and tested tips that have proven to deliver the best results.

1. Fill with water

Estimated time: 1 hour

Put the water hose in the hot tub and start filling it with water. The water level should reach 10-20 cm below the top ridge of the tub.

Use a 3/4 in diameter hose for faster filling and save time.

NEVER start the fire if the water has not reached the required level.

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2. Prepare the firewood in advance

You will need approximately 12-25 kg of firewood to heat up the hot tub once. Prepare different sizes of firewood in advance: make some kindling, finely chopped firewood, and then have your larger logs ready. Make sure you’re using kiln dried firewood to avoid smoke and ensure quick heating. Use hardwood (oak, beech, etc.) only or combine softwood (e.g. pine, fir) with hardwood in equal amounts.

Recommended size is 25-30cm long logs, split in halves and quarters.

Barkless firewood will produce less smoke.

Prepare finely chopped firewood for kindling.

Prepare larger logs to build and maintain the heat.

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3. Empty the ash drawer before starting the fire

Estimated time: 5 minutes

It’s not mandatory to empty the ash drawer every time, but do check it occasionally before starting the fire.

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4. Check the water level of the hot tub

The minimum fill level is 10-20cm (4-8in) below the top ridge of the tub. Once the water reaches the required level, turn it off and take the hose out. Put a floating thermometer into the water so you can observe the temperature.

NEVER start the fire if the water has not reached the required level.

NEVER empty the tub after bathing when the embers are still in the heater! Otherwise, put the fire/embers out and then drain the water.

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5. Start the fire with kindling

Estimated time: 10 minutes

Use some ready firelighters (avoid burning paper) and a long reach lighter to start the fire. Use kindling for building up the fire. Keep the heater air vents open. Check if the smoke is going out through the chimney top.

Use some ready firelighters and a long reach lighter to start the fire.

Start with softwood kindling for faster results. Continue with hardwood.

Place the firewood inside the heater as low as possible to avoid smoke coming out through the heater door.

Start with the heater door open for better airflow. Once the fire is going, close the door and leave the air vents fully open.

Cover the hot tub so the water heats up more quickly.

NEVER leave the fire unattended!

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6. Heat up the water

Estimated time: 2-4 hours

Heat up the water to the recommended temperature of 39ºC by burning medium sized firewood. If you just use large firewood as soon as you have the fire going, it will take longer to heat up the water and will produce more smoke.

Stir the water with a paddle or switch on the air jets to distribute the water evenly.

Check the fire every 15 to 20 mins and aim to keep the fire well alight.

Check the thermometer about 5 minutes after stirring the water to get a more accurate reading.

In 1 hour, the water temperature will rise by 7-10ºC.

NEVER leave the fire unattended!

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7. Enjoy the hot tub!

Estimated time: 1 hour

Once the water temperature has reached the desired level of 39°C, the hot tub is ready for use. Do not add any more logs to the fire! Close the heater air vents.

You can always drain some water out if there is too much in the hot tub.

If the water gets too hot, open the lid of your hot tub and let the water cool down for a bit before getting in.

You can add some cold water with the hose to make the temperature more comfortable.

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8. Maintain the heat

If you are planning to use the hot tub for longer periods of time, you can maintain the heat by placing some large firewood in the heater.

Use more hardwood at this stage as it will burn longer.

NEVER leave the fire unattended!

NEVER empty the tub after bathing when the embers are still in the heater!

Have the air vents open just a bit to keep a steady slow fire.

After the fire is out and you finish bathing, with the water still warm, put the lid on.

In summer, the hot tub will maintain the water temperature for quite a few hours.

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When choosing the best location and installing a base for a wooden hot tub, some pieces of information are no less important than your natural instincts.

First things first

Gardenvity does not offer a base preparation service for your hot tub. We can only provide detailed advice on a suitable location, materials and safety.

A Gardenvity wood-fired hot tub is a freestanding unit and is not designed to be sunk into decking.

A Gardenvity wood-fired hot tub is intended for outdoor use. If you want to place your hot tub under a roof (in a gazebo, pergola or other types of enclosure), you must consult with fire safety specialists and/or wood-fired stove installers who are aware of the relevant strict requirements in order to avoid any hazards.

It is crucial to ensure equal support under each contact point of the hot tub so that no single point is left hanging in the air. Over time, inappropriate support will result in deformations in the hot tub structure.

Any deviations from the requirements set out in the Gardenvity hot tub User Guide must be discussed with professional wood burning stove installers and your local fire safety authorities. You are fully responsible for any installation adjustments.

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1. Critical safety requirements when choosing a location

A wood-fired hot tub will have a smart wood burner installed. To adhere to general fire safety requirements, please ensure the following:

The chimney top is required to be kept at least 10 feet (3 meters) away from any flammable materials or buildings. The main part of the chimney shall be kept with a minimum 3.3 feet (1 meter) clearance from any object.

Any flammable objects or materials must not be kept close to the wood-fired heater. Protect the area around the heater door from accidental sparks that might still escape the heater when loading logs. Use tiles, sheet metal, sheet glass, or similar protection – just like you safeguard the wooden floor at a fireplace.

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2. Necessary calls prior to installation

Gardenvity’s Customer Experience Specialists will answer most of your questions. Our phone number is the first one you should dial when you want to make sure you’re making good decisions in terms of choosing a location and base for your hot tub. And yet, there will be situations when we may have no power concerning your personal situation.

Contact your local council to find out if you live in a smoke control area and, if so, read the applicable rules carefully.

You should consider locating a wood-burning hot tub in a suitable place that will reduce the risk of smoke nuisance occurring within neighbouring properties.

A taller chimney (you can get an optional extension flue from Gardenvity) and quality firewood (kiln-dried, barkless) can significantly reduce the impact and ensure lingering smoke is minimised.

If you plan to install your hot tub in a gazebo, a pergola or any similar type of enclosure, find an experienced wood-fired stove installer and consult with a fire safety specialist.

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3. Area needed for my hot tub

To plan a decent area for your hot tub, consider the size of your chosen hot tub, the type of steps you decide to order, and that you need to leave space around the tub for service and maintenance works. Wide and open accessto the heater, servicing compartment and water drain valve will ensure comfort and great ease of use.

Please refer to the below image with indicated measurements of the base needed for the different models of Gardenvity wood-fired hot tubs.

The size of the required base varies depending on the size of your hot tub (for 1-2, 6-8 or 8-10 people), its shape and the type of stairs (standard or curved).

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4. Suitable materials for the base

A Gardenvity wood-fired hot tub will weigh approximately 2000kg (4400lb) when filled with water (the figure for the 1-2 seater model is around 1500kg (3300lb)). Your base must be strong enough to bear the load + the combined weight of everybody who will get inside the tub! Below are the most popular choices for preparing a base for a wood-fired hot tub.

You’ll need to make sure the log burning hot tub base is placed on an even and stable surface. If necessary, use level chips to create an even base.

A gravel base with stabilisation grid and concrete slabs are the easiest to install.

You may place the hot tub on a wooden or recycled PVC deck for the best visual appeal.

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5. Best practices and practical tips

Allow us to share a few small details that will increase your hot tub’s longevity.

The best option for a wooden hot tub base pad is a concrete structure, pavement slabs, or gravel. Such a base will ensure proper stability and favorable conditions for its wooden parts, as they will not absorb moisture from the ground.

If you place your hot tub on gravel, keep it lifted 4 inches (10cm) above the ground for proper air circulation.

The easiest way to do that is by tucking concrete slabs under the contact points of the tub.

It is crucial to ensure equal support under each contact point of the hot tub so that no single point is left hanging in the air. Over time, inappropriate support will result in deformations in the hot tub structure.

Observe the contact points of the different Gardenvity hot tub models below.

The Gardenvity Premium hot tub for 8-10 people has more contact points at the bottom, so we recommend resting the tub on larger pavement slabs as shown below.

Ensure there is no thick flora around your hot tub. Vegetation hinders the wooden parts’ ability to breathe and, in turn, promotes decay.

Following our advice, you’ll be now ready to bring your hot tub in for the cosiest soaks or family gatherings marked with joy and laughter.

Happy hot tubbing!

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To ensure perfect water clarity and efficiency, Gardenvity wood-fired hot tubs use sand filters with fibre balls as a standard. Sand filter has been the oldest water filtration system used in swimming pools, commonly using natural filtering media – hence their name.

The technology has been significantly improved by replacing sand with more effective modern filtering media, such as fibre balls to trap smaller particles (down to 5-3 microns compared to 35-20 microns with sand).

The modern filtering media also plays an important role in reducing energy consumption, keeping the filter pumps under lower pressure. What is more, the fibre balls can be recycled to make it an environmentally friendly solution.

1. The key benefits offered by a sand/fibre ball filter

Our sand/fibre ball filter is designed to be used with lightweight and environmentally friendly fibre balls. We must make it clear that the type of sand filter used in our products cannot be used with sand for filtering the water – it’s a sand filter in name only. This type of filtration is preferred by users who value the long service life of the filtering media. The fibre balls used in a water filter serve 2 years. The maintenance work during those years involves nothing more than occasionally cleaning the fibre balls. You will not have to worry about buying filter cartridges regularly, as is the case when using cartridge filters.

Long service life.

Easy, low-cost maintenance.

Good performance, trapping impurities of 10-3 microns in size.

Environmentally friendly solution.

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2. Fibre balls for your convenience: do they do the job well?

Using fibre balls instead of sand seems to be an all-around perfect solution for keeping the water clean in the hot tub because:

They capture debris and dirt effectively (down to 10 microns – or even to 5 or 3 microns, as some manufacturers claim).

They require little maintenance work – a simple hand wash or in a washing machine.

They are incredibly lightweight.

They reduce energy consumption.

They are environmentally and cost-friendly.

To answer the question if the filter balls clean the water in a hot tub effectively, it’s a YES, absolutely! Pool and hot tub owners report that they actually do a better job trapping debris and dirt while requiring less maintenance. Since the polyethylene fibre offers excellent porosity and does not clump or harden over time, the whole filtration cubic area is effectively employed to remove the particles from your hot tub water. It also means that the water flows more easily through the bed of filter balls, reducing the pressure needed from the filter pump (therefore, lowering energy consumption) and increasing the service life of the pump.

If you notice sediments on the hot tub bottom, this does not show failure in the filter performance. Simply switch the massage system on to move the particles with water, and the filter will trap those impurities.

Fibre filter balls have to be cleaned by taking them out to soak and wash manually or in a washing machine (please, put them in a washing net when doing so!). In both cases, filter balls are there to last a long time with very little wear. The good news is that the balls are recyclable after a few years of usage, making it a highly environmentally friendly solution.

500g of filter balls replace 18kg of sand, which in other words means that they are more than 30 times lighter, and thus, more practical for shipping and disposal.

Finally, filter balls are cheaper than the special sand used in water filtration. You can get filtration balls at most pool stores, e.g., on Amazon.

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3. How often do you have to change the water in a wood-fired hot tub?

With the combination of sand/fibre ball filter, UV-C module and water sanitisers in the Gardenvity Premium wood-fired hot tubs, it is possible to keep the water in the hot tub for a few months. A water filter removes debris and a UV-C lamp and chemicals kill bacteria. You have to do both and follow the manufacturers’ instructions carefully for best results. Without water treatment, you should change the water in 1-2 days after 1-2 uses.

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4. What should I know about the usage and maintenance of a sand/fibre ball filter?

As a standard, maintenance works with a sand/fibre ball filter includes the following:

Timely cleaning of fibre balls. Typically, you’d expect to see the pressure gauge needle going up, signalling you to backwash, but not with the fibre balls. We recommend that you inspect the fibre balls inside your filter every 3 months and clean them if needed. However, it will largely depend on usage and quality of the water. Use a little trial and error to find the best schedule for your hot tub. When you keep fibre balls clean, you’ll have better filtration, water flow and clearer water.

Cleaning the filter strainer to remove the larger debris restrained at the water pump inlet when you see it.

Changing fibre balls when they lose effectiveness. This has to be performed at least once in 2 years. This operation requires more work than, for example, replacing a cartridge, but it’s worth the effort due the environmental advantage of using recyclable fibre balls.

Please bear in mind that when using the sand/fibre ball filter to remove debris and particles, you still need water treatment chemicals to kill the bacteria.

As you can see, there are not so many points included in your maintenance schedule.

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5. What are the expected maintenance and operation costs of this filter?

When you need to estimate the cost of maintenance and operation of the sand/fibre ball filter, you need to weigh in the replacement fibre balls and the electricity needed to power the filter motor. Here’s your summary:

Year 1 – none*
Year 2 – none*
Year 3 – fibre balls, £20
Year 4 – none*
Total in 4 years: £20

Power costs

Working at 250W power, based on current average electricity price in the UK (which is 34p/kWh in Q1 2023), the sand/fibre ball filter would consume £0.085 per operating hour. The water filter needs to be run 4-5 hours daily when the hot tub is filled with water. Thus, if your Gardenvity wood-fired hot tub is used all year-round, you’re looking at around £12.50 a month.

* You will only need to wash the fibre balls either by hand or in a washing machine (put them in a washing net when doing so!) every few months. This will cost a bit of your time, water and electricity – which is just minimal and hard to convert into specific amount of pounds.

To sum it all up, a sand filter for water cleaning in a hot tub is meant for those who value long service life, quality performance, and ease of maintenance. Combined with the modern sand alternative – filter balls – the care is easier with fewer pounds to carry home and less strain on the environment since the polyester balls are fully recyclable.

Check our other articles for more practical tips and advice on the usage and maintenance of the sand filter in a Gardenvity wood-fired hot tub.

Happy hot-tubbing!

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