Too hot in the hot tub?

How hot is hot enough, how hot is too hot?

We search for an answer to the question “What temperature should I set my hot tub at?”

In the depths of winter, the feeling of lowering yourself into the warm and inviting water of your hot tub is one to be savoured.  If you’re anything like us, the temptation is to set the temperature to the maximum setting and leave it there.  Simple?  But choosing the right temperature depends not only on your personal preference – your families or guests health & safety, not to mention your budget will need to be considered as well, before you find the goldilocks zone of not too hot, not too cold that works best for everyone.

Adjusting the heat of your hot tub is a straightforward affair – most have a simple push button menu on the control panel while some models allow you to control your hot tub heat settings from the convenience of an app on your phone, tablet or PC.

Hot Tub Touch Screen Control Panel

The maximum temperature setting as stated in the European Standard for domestic spas and hot tubs (BS EN 17125) is 40° C / 104° F.  No reputable hot tub brand will manufacture a tub that exceeds this setting.  Even though your hot tub will have a temperature limiting device, keeping a separate thermometer handy is best practice – that way you’ll be able to quickly and easily confirm your spa water temperature and identify any potential problems, such as overheating or heating failure, before you get in the water.

Is 40°C too hot?

As your body temperature increases to the point where it reaches or exceeds 39° C / 103° F, there is an increasing danger of developing several conditions related to hyperthermia (excessively high body temperature), ranging from mild to seriously life threatening.  These may include:

  • Heat rash
  • Heat cramps
  • Heat stroke
  • Heat exhaustion


older couple in hot tub

The risk of serious complications becomes even higher for older people, younger children, pregnant women, and those with chronic illnesses or conditions such as a heart condition, high blood pressure and diabetes.

Even if you’re in overall good health, spending excessively long periods of time in hot water can be dangerous.

What are the recommendations for children using a hot tub?

HSG 282 (published by the UK Health & Safety Executive) states that children under 4 years of age should not be allowed to use a spa.  In the USA the CDC (Centre for Disease Control & Prevention) sets the minimum age at 5.  This is partly due to water safety, but also has an element of temperature consideration – as children don’t have the same heat tolerance as adults. Their smaller bodies and thinner skin make them more susceptible to heat.


At the maximum recommended water temperature, children should not use the hot tub for more than 5 minutes at a time. Dropping the water temperature by a few degrees – to 36.5° C / 98° F will allow for a longer soak, but even this should be limited to a maximum of 15 minutes.  To reduce risk of children overheating, sitting on a booster cushion is also a good idea – as in this way young children avoid full body immersion, allowing their bodies to regulate heat more effectively.  Never allow children to use a hot tub unsupervised.

Can I use a hot tub if I’m pregnant?

If you are, or may be pregnant, the current NHS advice is to avoid using hot tubs due to the risk of over-heating, fainting or dehydration.  It’s possible that a significant rise in your core temperature could be harmful in pregnancy, particularly in the first 12 weeks.  With regard to water temperature the NHS website makes the following statement, “If you’re exercising in water, such as at an antenatal class, the temperature of the water should not be above 32° C.

If you’re using a hydrotherapy pool, the temperature should not be above 35° C.”  If you’re past the first trimester and you feel you want to use the hot tub, do so only after getting your doctor’s approval, and use the tub for no more than 10 minutes at a time and allow for plenty of cooling off in between sessions.

How do I find the right hot tub temperature?

Having taken into account the above safety considerations, your perfect spa soak temperature will probably vary depending on the time of year – for example on a hot summers afternoon, you might enjoy a refreshing cooler dip than you will for a mid-winter soak as snow is falling around you.

A good starting point is the average normal body temperature, 37° C / 98.6° F.  If it’s too chilly, slowly increase the temperature until you’re comfortable.  The stress reducing effects of your spa are lessened as water temperature drops – so don’t go too low!

Can I save money by reducing the temperature of my hot tub?

How much energy your hot tub consumes heating the water was probably an important consideration when deciding whether to buy a tub.  Premium hot tubs have high levels of insulation and you can supplement this with a floating heat retention cover and a good quality, good condition hot tub cover. You might also think about lowering your hot tub’s heat setting when you’re not using it for longer periods to cut your energy costs.

But beware, if you use your hot tub regularly and lower the temperature setting between each use, you might actually increase your energy costs.  This is because reheating the hot tub water each time not only burns extra energy, but also your spa’s heating element has to work harder to raise the water temperature than it does to maintain it. This can wear it out more quickly than a more balanced load, perhaps requiring you to replace it more often if it burns out.

I’m going away on holiday, can I lower the temperature of my hot tub?

If you don’t plan to use your hot tub for a longer period of time, dropping the temperature is a great idea as this can help you avoid a high energy bill when you return.  Most hot tubs have an economy or holiday setting that will maintain much lower water temperatures.  Just beware if ambient temperatures are around freezing, setting the spa too low or even turning the heater off risks burst pipes and potentially some expensive damage to pumps and other hardware.

So having settled on the best blissful temperature for you, what’s left now?  Just enjoy relaxing safe in the knowledge that you are enjoying the very best hydrotherapy for mind and body!

Should I Install a Wood-Burning Hot Tub in my Holiday Let?

Wood burning hot tubs have a definite aesthetic appeal and offering a hot tub in holiday let setting is something of a must have.  If you’re considering installing a wood-fired hot tub in your holiday property – don’t decide until you’ve read our guide.

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Hot tubs for holiday cottages are something of a must have.

For example, Sykes reported the following finding:

A hot tub will:

  • Boost your occupancy rates
  • Raise your property profile on web searches
  • Allow you to increase your rental charge
  • Increase guest satisfaction
  • Improve re-booking rates

They are a huge win.

Infographic - Properties with hot tubs make 54% more than other properties in the same region.

How do I create a point of difference?

One suggestion that we frequently hear, including from some Holiday Let agencies is that a wood-fired hot tub would be the way to go.  With their aesthetic appeal, they can certainly look more in keeping with a period property and might attract the eco-conscious holiday-maker.  For example, this hot tub from Skagards fits into it’s surroundings perfectly.


Are they a good idea for you as the property owner, or your guests?

The first thing to be aware of is that the use of any type of hot tub within a commercial setting is subject to certain rules.  If you own a holiday home that you let out to paying guests and supply a hot tub (that only one group of people at a time are able to use) then you will need to be compliant with the “Domestic hot tubs in a business setting” guidelines.   These guidelines are known as HSG282 and are designed to ensure that the hot tub water used by your guests is safe and clean and as the owner you are held legally responsible for compliance.  This isn’t the interfering nanny state – an improperly maintained hot tub can harbour serious infectious diseases, including the potentially fatal legionella bacteria.

HSG282 from HSE
Legionella Bacteria

As a guideline, in order for your hot tub to be compliant with HSG282 you should at least:

  • Have a built-in inline Chlorine or Bromine feeder or install one (SpaPal)
  • Empty the water after each hire (or after a week, whichever comes first)
  • Test the sanitiser (chlorine/bromine) & pH twice daily
  • Monthly microbiological tests
  • Quarterly Legionella tests

This is where the type of hot tub you install becomes critical.

HSG 282 Compliance with a wood fire heated hot tub:

With a wood fired hot tub, there is no filtration system.  The water is heated by a simple stove.  There are no pumps, no pipework, no water circulation or filtration system.  What this means when it comes to maintaining clean water is that you can’t install an inline dosing system for sanitiser as required by HSG282.  This doesn’t immediately rule out a wood-fired hot tub from a holiday let setting, but it does mean you have to adapt your approach.  Whereas for an electrically heated hot tub, you can leave the water in the tub for up to a week, with a wood-fired tub you need to drain down the water after every use.  You cannot leave it filled for the duration of the rental. Of course if your guests want to use the hot tub more than once during their stay, what is emptied must be refilled, and then reheated.

Heating a wood fired hot tub:

Ah!  Heating.  The joy of a wood-burning stove is the satisfaction of making and lighting your own fire.  The same joy isn’t always felt trying to get the fire to take, when it’s sub-zero temperatures and the fire keeps going out.  Fire making might be a relatively simple activity that humankind have mastered for millenia, but not all of your guests will be adept at building and making a fire.  Not forgetting the chores of clearing and resetting the stove after each use.  Depending on the volume and temperature of the water and air around it, a wood-burning hot tub might typically take 3 hours or longer for the water to reach temperature.  No quick spur of the moment dips then!

sauneco wood burning hot tub stove

A wood burning stove looks gorgeous

but is it safe in a holiday let setting if your guests have children?

Maintaining a safe water temperature in a wood fired hot tub:

Ah!  Temperature.  Most people enjoy a water temperature of between 36-39 degrees C.  Electrically heated hot tubs have a thermostat which stops the water temperature getting dangerously high (Above 40 degrees C).  This is important – if water is above this temperature, the excessive heating can cause heart attack, heat stroke, brain damage and even death.   This might sound a little extreme if you are one for a hot bath, but unlike in a hot tub, bath water gradually cools while you are in it.  Also in most baths you are not fully immersed in the way you are in a hot tub, so your core temperature can stay cooler even in hotter water.  With a wood-fired hot tub there is no thermostat and no circulation of the water, so in order to manage the temperature, you will need to provide a floating thermometer.  Not a big deal you might think, but you are relying on the guests to effectively manage this.  Would you be confident that your party of guests would keep a close eye on the water temperature?  An added complication is that the water may continue to increase in temperature even after the stove is shut down – it can get extremely hot!  First-time users may not understand how to safely manage a wood-fired spa.

steamy toes in a hot tub

Which type of hot tub is right for your holiday let?

How about the experience?  There is no denying that wood-fired hot tubs look good and have an olde worlde charm and appeal.  However, the user experience isn’t quite the same as with an electric hot tub.  They do just offer heated water.  No Jets or Pumps.  No hydrotherapy.  A relaxing soak is nice, a soak and a massage is nicer, in our opinion!

So can you get a wood-fired hot tub for your holiday let?  Yes!  You certainly can.  But for most holiday let owner / operators, the level of involvement and maintenance, coupled with safety concerns makes them unfeasible.  The reality is that they are also likely to provide a much less enjoyable experience for your guests than an electrically heated tub.

Our recommendation is that if the styling of an electrically heated hot tub is not to your taste, the best way to manage this is by concealing the cabinet with a gazebo, planters and other outdoor decorations that can soften the finish.  Making a real feature of the hot tub in your outdoor living space is the way to go!

BISHTA are the British & Irish Spa & Hot Tub Association.  BISHTA exists to promote high standards of safety, enjoyment and value within the hot tub industry.  They have also provided advice regarding installing Scandinavian type hot tubs in Business Settings.  Click on their logo to read the article.

how to test the pH of your swimming pool or hot tub

All About pH!

A balanced pH level in your hot tub / spa / swimming pool water is an essential starting point in maintaining water quality.  Check out our list of the most Frequently Asked Questions & our answers on:

“How To Manage Your Water pH.”


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pH Scale

What does the pH level measure?

pH is a measure of how acidic/basic water is. The pH range goes from 0 to 14, with 7 being neutral. A pH of less than 7 indicates acidity, whereas a pH of greater than 7 indicates a base. The pH of water is a very important measurement concerning the water quality of your hot tub / spa or swimming pool.

What should the pH level of my hot tub / spa / swimming pool water be?

The sweet spot you are aiming for is a pH level of 7.4-7.6


How do I measure the pH level of my hot tub / spa / swimming pool water?

You can do this using one of three methods:

Pool Lab Photometer Bluetooth Water Testing Kit
Check hot tub water pH

How Often should I check the pH level of my water?

This depends on several factors – in a commercial environment, at least daily.  In a home setting it depends on how balanced and stable your water chemistry is.  At least 2-3 times a week is a good guideline.  If this sounds wasteful or expensive in time and test strips, consider the effects of unbalanced water.

Is testing & maintaining pH levels in my hot tub / spa / swimming pool water expensive?

Consider the costs of poorly balanced water:

  1. Reduced equipment life. Unbalanced water will cause serious damage to the fixtures and fittings of your hot tub, swim spa or pool. The cost of replacing this equipment, especially things like pumps, heaters and salt systems, greatly outweighs the cost of maintaining proper water balance.  Damage caused by poor water chemistry is often obvious and the parts worn out by these means are unlikely to be covered by a manufacturer’s warranty.
  2. Water quality problems. The cost of properly maintaining your water is a fraction of the cost of remedying problems like green or cloudy water when they have developed. Fixing these water quality issues generally costs more than the balancing chemicals required to prevent them from occurring in the first place.
  3. Increased sanitizer usage. The effectiveness of sanitizers (chlorine & bromine) changes significantly with the pH of the water.

My water looks really clear – doesn’t that mean my pH levels are fine?

Without a pH test, there is no way of knowing.  Water that looks clear can sometimes be hiding serious problems.  Acidic water is capable of holding a lot of minerals in solution without the water turning cloudy. This might look good but isn’t good for you or your spa equipment.

Crystal Clear Hot Tub Water
Milky, cloudy, foaming hot tub water

My hot tub / spa / swimming pool water looks cloudy – does this mean my pH levels are unbalanced?

Cloudy water is often a sign that your pH levels are too high.  This would be the first thing to check if your water is cloudy, milky or foamy.  However cloudy hot tub water can also be caused by a number of other factors and these should all be checked and addressed as necessary.

What effect does pH have on the effectiveness of my sanitiser?

The disinfectant power of Chlorine is relative to the temperature and pH of the water. As pH increases, chlorine becomes less effective.  This means you have to add more chlorine to achieve the same results.  As pH decreases, the chlorine becomes more effective – but acidic water brings other undesirable issues (see Why is low pH in my hot tub / spa / swimming pool water a problem?)  So what we are aiming for is a balance – ideally around pH 7.4

pH   Effectiveness of Free Chlorine
6.0   97%
7.0    75%
7.2    63%
7.5    49%
7.6    39%
7.8    28%
8.0    3%

Why is low pH in my hot tub / spa / swimming pool water a problem?

PH levels below 7.2 could spell trouble for you and your spa. Acidic water makes it more likely that your chemical sanitizer will “burn out” quickly, leaving you exposed to potentially dangerous contaminants and bacteria.  Acidic water will corrode spa components such as headrests or jets. These can be expensive to replace.

Acidic water will potentially:

  • Corrode metal components
  • Damage pump seals and other spa components
  • Damage the acrylic shell
  • Burn out chlorine/bromine sanitiser so that you need to use more
  • Give bathers dry, itchy skin and stinging / burning eyes – human tears are pH 7.4
An image of 1kg pH Plus

My water pH is low, how do I increase the pH level of my hot tub / spa / swimming pool water?

The most common pH increaser, pH raiser, pH plus / pH + products available to treat low pH in hot tubs contain the active ingredient sodium bicarbonate.  Sodium bicarbonate is effective at increasing both pH and TA.

Why is high pH in my hot tub / spa / swimming pool water a problem?

When your pH level goes above 7.6, your spa water can be described as ‘basic’. This essentially means your spa water will be poorly sanitized.  Basic spa water can result in a flaky scale build up around your spa surfaces. The scale is due to a build-up of calcium caused by the high pH. Cloudy water is also another symptom of high pH levels.

Basic water will potentially cause:

  • Calcium build up
  • Damage pump seals and other spa components
  • Leave marks and staining on the acrylic shell
  • Give bathers dry, itchy skin and stinging / burning eyes – human tears are pH 7.4
  • Chlorine / bromine sanitiser becomes much less effective and the need to use more
  • Cloudy water and a gritty feel on hot tub surfaces
White Flakes in hot tub water
An Image of Relax pH Minus Granules 1.5kg

My water pH is high, how do I reduce the pH level of my hot tub / spa / swimming pool water?

pH decreaser, pH reducer or pH minus / pH– is a dry acid balancer, that you pre-dissolve in warm water then add to your hot tub / spa / swimming pool water.  The active ingredient in pH decreaser is usually sodium bisulfate.  Adding this will also lower Total Alkalinity, sometimes so significantly you’ll need to increase your TA back up a little afterward.

Can I Use Muriatic Acid to lower pH level?

You can, but keep in mind that although Muriatic acid provides an alternative way to decrease both pH and TA, it is an extremely caustic chemical.  You must store it safely and use protective glasses and chemical-resistant gloves and a great deal of caution when working with it – you really don’t want that burning your skin.

You won’t be able to just pour some in your spa, either. Muriatic acid will need to be diluted, added to your spa water, then aerated by running the spa jets. Finally, leave the spa to circulate overnight before retesting your water.

We don’t supply Muriatic Acid at Castle Hot Tubs.

Can I use Cyanuric Acid to lower pH level?

No.  Cyanuric acid technically is an ‘acid’ but it is not like muriatic acid.  It has little overall effect on pH, alkalinity or hardness and should not be used for the purpose of lowering pH levels.

Should I use Bromine or Chlorine sanitiser if my pH is unstable?

Bromine is slightly more effective in an unstable pH environment.  But this isn’t really a basis for choosing which sanitiser to use.  Achieving a balanced pH water is a necessity, whichever sanitiser you use.

How do I stabilise the pH level of my hot tub / spa / swimming pool water?

Adjusting the Total Alkalinity is likely to help.  The term technically refers to the ability of a solution to neutralize acids—or buffer them.  In your hot tub/spa or swimming pool water, the importance of measuring TA is only slightly different. TA acts as a buffer for the pH level in your water, helping to keep the pH level stable.

Total alkalinity is important to your water balance, the first step in your water care process should be measuring and adjusting TA before adding any other chemicals. The ideal range for TA is 125 parts per million (ppm) to 150 ppm.

When you adjust your alkalinity, add small doses, one at a time.  Allow the dose to circulate before testing again.  Only after your TA is in the optimal range should you move on to adjusting pH.  Achieving the right TA may get your pH in the target range.

An image of 1kg Relax Total Alkalinity Plus
Aquafinesse Spa Clean Tablet

I can’t get the pH level of my water balanced – should I “re-pHresh”?

If you find yourself chasing high and low pH in your hot tub / spa water, the easiest option might be to drain your spa and start over. This might not be such an attractive option if you’re operating a swimming pool.  If a drain and refresh is the way you want to go, the day before you drain, add some spa clean tablets and run your jets to clean out anything that could be affecting your water chemistry. After draining, clean the interior of your spa.  Before re-filling consider using an in-line pre-filter that can easily be attached to your hose, ensuring that your fill water is free from contaminants.

We hope you have found our guide to achieving balanced pH levels in your hot tub / spa or swimming pool useful.

Check back regularly as we add to our Water Quality FAQs!

The Shocking Truth About Hot Tubs!

Let’s face it, neither the term “shock” or “dose” are words that we associate with particularly pleasant events.  You might have heard that it is sometimes necessary to combine these two words into “Shock Dose” as part of your water treatment routine for your hot tub / spa or swimming pool.

Is this a bad thing?

Does it mean you’ve failed as a responsible hot tub owner?

We investigate and explain the shocking truth!


Granular Shock Treatment, Relax 1Kg container. Non stabilised chlorine shock granules for shock dosing or oxidisation of hot tub, swimming pool & spa water

What is chlorine shock dosing?

A chlorine shock dose is when you add a larger quantity of chlorine to your hot tub water in order to break down waste products and contamination in order to re-establish clean water.

What is non-chlorine shock dosing?

Non-chlorine shock doesn’t contain chlorine itself, and does not disinfect the water.  Non-chlorine shock helps the chlorine already in your hot tub work better by oxidising the water and creating “free chlorine” – which is what is needed to kill bacteria.  For those using bromine as a sanitiser, Non-chlorine shock will also activate bromine, helping it work more effectively.

An image of 1kg Relax Non-Chlorine Shock
Legionella Bacteria

Why do I need to shock dose my hot tub water?

Shock dosing your hot tub water will help to prevent the build-up of bacteria, viruses and algae and it will prolong the life of your spa.

What are the benefits of shock dosing my hot tub?

Shock dosing your hot tub water will keep it clear, clean safe and comfortable to use for longer.  It helps reduce the need for excessive draining and re-filling of your hot tub.

When should I shock dose my hot tub water?

  • Before use, on the first fill of your hot tub
  • Any subsequent drain and re-fill
  • At the first sign of any algae or slime
  • After a period of heavy usage
  • After any loss of water clarity
  • If the hot tub hasn’t been used for a while
Green hot Tub Water

Should I use a chlorine shock or a non-chlorine shock?

Chlorine shock is suitable for commissioning a new hot tub, after a fresh water change or after very heavy use.  Because it will raise chlorine levels you may have to wait for the chlorine level to reduce before you can allow bathers to safely use the hot tub.  If you use Bromine as a sanitiser, you cannot use chlorine shock.

Non-chlorine shock does not disinfect the water, it helps the existing sanitiser (chlorine or bromine) to work better and more effectively.  You can generally use the hot tub sooner after adding non-chlorine shock.

Is it safe to chlorine shock dose my hot tub water?

Shocking your spa water is an important part of your maintenance routine.  But high chlorine levels can be dangerous, so it is very important that no bathers are in the water when adding chemicals.  To ensure that the water is safe, ensure that chlorine levels have dropped below 5ppm before allowing bathers back into the water.  Chlorine levels should be checked with test strips.

3 Way Chlorine Test Strips

How do I Chlorine Shock Dose my hot tub?

Dissolve the chlorine shock granules.  Add the chlorine shock mixture directly to the water with the filtration / circulation pumps running.  Never shock dose the water with the circulation turned off.  Leave the hot tub cover off for at least 20 minutes.  This will prevent chemical damage to the cover and pillows of your hot tub.

My hot tub water smells strongly of chlorine what should I do?

When chlorine combines with organic waste (body fluids, dead skin etc) it produces a compound called chloramine.  This gives off a strong chlorine odour.  This is often mistaken for too much chlorine but is in fact an indication that the chlorine has been “used” up.  A shock treatment will breakdown chloramine so it can be easily removed from the water, “freeing up” your chlorine to work more effectively.

My hot tub water is cloudy what should I do?

Us humans carry organic compounds on our skin, such as oils, cosmetics, lotions and dead skin itself.  This quickly accumulates in hot tub water and can cause it to become cloudy.  Shock dosing the water will help to remove these compounds and assist in clarifying and cleaning the water.

Cloudy hot tub water

We hope you have found our guide to shock dosing your hot tub, swimming pool or spa useful.  So don’t let the name put you off, it’s an important part of your water care routine.  Check back regularly as we add to our Water Quality FAQs!

Chlorine tablets on the side of a hot tub.

All About Chlorine!

Used properly chlorine can be your best friend in maintaining hot tub water quality.  We have compiled a list of the most Frequently Asked Questions about chlorine to help that friendship progress a little more smoothly.


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Chlorine tablets and granules for hot tubs.

Should I use chlorine granules or chlorine tablets in my hot tub?

Chlorine is an essential part of your tool kit for maintaining a healthy and enjoyable spa.  As a hot tub owner, you’re probably already aware that chlorine can be added to your hot tub water in two different forms:

But you may have wondered, does it make a difference whether I use chlorine tablets or chlorine granules in my hot tub?  Does one form of chlorine work better than the other?  Let’s find out!

Should I use Chlorine Granules in My Hot Tub?

The benefit of using chlorine granules is that they are quick to dissolve and relatively pH neutral.  This makes chlorine granules ideal for shock-dosing on initial set-up with fresh water, or if the spa hasn’t been used for a period of time.  Chlorine Granules will raise chlorine levels more rapidly than chlorine tablets.

An image of 1kg Relax Stabilised Chlorine Granules
An Image of Relax 1kg Chlorine Tablets Small

Should I use Chlorine Tablets in my hot tub?

Chlorine tablets offer a more “hands-off” approach to maintaining your spa water.  Chlorine tablets release chlorine slowly, making it easy to maintain a consistent level of chlorine in the water over a longer period of time.  If you are going away for a few days or have limited time to sort out the water chemical levels, chlorine tablets are a good choice for you.

Is it easier to use chlorine tablets or chlorine granules in my hot tub?

It really depends on how you use the tub!  If you don’t use your hot tub very regularly and need to shock dose often, chlorine granules may be more convenient for you.  If you want to maintain a consistent chlorine level you will need to schedule adding granules to your spa – this may become a hassle for you.  Regular spa users may find tablets more convenient.  Getting the correct chlorine levels set initially may take some experimentation, but after that, as long as you make sure that you have replaced the tablets once they have dissolved away they are fairly hassle free.

Adding Chlorine granules to a hot tub

How do I add Chlorine Granules to my hot tub?

You can add chlorine granules to your spa water simply by sprinkling them directly into the water (as long as the water temperature is greater than 20° C).    However, this method does carry a risk!  If the granules settle on the acrylic surface of your spa and do not dissolve this may cause damage which is very unlikely to be covered by the manufacturers warranty.


If the water temperature is less than 20° C, if you are unsure of the water temperature, or if you want to avoid potential damage to acrylic surfaces, then the best method is to pre-dissolve the chlorine granules in a clean plastic bucket.  Never add water to the chlorine, fill the bucket with water first then add the chlorine.

Add the dissolved Chlorine Granules when the pumps are on, and near to the water inlets as this will aid the distribution of chlorine around your spa.

Don’t get carried away!  You don’t want to over-chlorinate your water.  So just add one dose at a time.

How much Chlorine Granules should I add to my hot tub?

A little maths is required!

2g of Chlorine Granules will increase the chlorine level of 1,000 litres of water by 1mg/l (ppm).

If you are pre- dissolving your granules in a bucket of water you can follow this formula up to a maximum rate of 10g Chlorine to 1 litre of water.  To be accurate you will need to know the volume of water in your hot tub.  Alternatively, you can add a little chlorine at a time, allow it to circulate and then test and re-test until you achieve the chlorine level you are aiming for.

Chlorine Dispenser for 20g Tablets

How do I add Chlorine Tablets to my hot tub?

The amount of chlorine released is controlled by adjusting the dial of a floating chemical dispenser.  A little bit of trial and error might be needed at first to find the sweet spot on your chemical floater that maintains the desired levels of chlorine. However, once you have found the level that works for you it should be relatively easy to keep chlorine levels consistent.

How often do I need to replace chlorine tablets?

Chlorine tablets will typically erode over a period of 3-5 days, depending on the amount of water flowing over them.

How do I know if I have added enough chlorine to my hot tub?

Before bathing, you should check the chlorine level is within the range of 3-5mg / l (ppm).  You can check your free chlorine levels with test strips.  If you want increased accuracy with your water testing, digital test readers are available.


Help!  I’m allergic to chlorine!

A lot of people think they are allergic or intolerant to chlorine.  For most people this isn’t the case.  Water pH levels play a huge role in how comfortable we are in water.  Water that is either too acidic or too alkaline will irritate our skin, eyes and sinuses.  The water pH must be balanced and neutral for water that is comfortable and also for the sanitiser to work effectively.

3 Way Chlorine Test Strips
Aquafinesse Hot Tub & Spa Water Care System Switch Kit

How Can I Use less chlorine in my hot tub?

High levels of chlorine can be undesirable.  The keys to maintaining safe and healthy hot tub water while using lower levels of chlorine as a sanitiser are:

    • Keeping pH levels balanced – ideally close to pH 7.2
    • Use AquaFinesse to eliminate bio-film

At a pH of 8, over half of chlorine added to your hot tub water is ineffective.  At a pH of 7.2 this rises to 90% – chlorine which is actively available to kill algae and bacteria.

Biofilm, a type of slim can form which provides a safe shelter for bacteria allowing them to breed virtually unmolested by chlorine or any other sanitiser.  AquaFinesse breaks this shelter down allowing smaller amounts of chlorine to be more effective.

My hot tub water smells strongly of chlorine what should I do?

When chlorine combines with organic waste (body fluids, dead skin etc) it produces a compound called chloramine.  This gives off a strong chlorine odour.  This is often mistaken for too much chlorine but is in fact an indication that the chlorine has been “used” up.  A shock treatment will breakdown chloramine so it can be easily removed from the water, “freeing up” your chlorine to work more effectively.

Do I have to use chlorine in my hot tub?

No.  You don’t have to use chlorine.  But you do have to use a water sanitiser.  For most people chlorine is the safest and most effective sanitiser to use in their spa.  An alternative sanitiser is bromine.

We hope you have found our guide to using chlorine in your hot tub or spa useful.  Check back regular as we add to our Water Quality FAQs!

An image of a 1kg bottle of Relax Bromine Granules Hot Tub / Spa Sanitizer

How to Protect your Hot Tub in Storm Winds

The UK is set to reap the whirlwind of climate change with the huge damage caused by wind storms expected to increase sharply, according to the ABI (Association of British Insurers).  Our minds are focused when the MET office issues a severe weather warning, with named storms seeming to be ever more frequent – but the time to act to ensure the safety of your loved ones – and your valuable property is in the calm spells in-between.

As a hot tub owner, it makes sense to protect your investment.  A little time and preparation beforehand might just save you a lot of time and money later!

The Potential:

A hot tub cover is just the right size and shape to catch an aggressive gust of wind, ending up being thrown off the cabinet and providing a very effective sail, but causing a lot more damage when it eventually returns to ground.  The impact will damage your cover causing the vinyl and foam to crack and be compromised, making it less effective or even useless.  It it collects some garden furniture or plants or even worse ends up cartwheeling across the paintwork of your neighbour’s shiny new car things could soon start to get really ugly.


Replacement Hot Tub Cover Clips

Keep your hot tub cover in place using cover clips

Storm Straps

For more severe winds, peace of mind can be achieved by investing in storm straps.

EasyKlip Repair Kit

If you already have straps, check their condition from time-to-time.  Repair kits are available to ensure that in a time of testing, your storm straps will be up to the task.

Don’t be too over-zealous when tying down your hot tub cover – overtightening could cause damage to the foam core.  Make sure the straps are taut and that should be enough to keep things snug and in-place. 

If you don’t have time to get some straps and the weather bomb is imminent you could try to improvise straps that wrap around the whole cabinet.  The big no-no here is that you should never place heavy objects on the hot tub cover in an attempt to keep it from blowing away. Breeze blocks, bricks, and other heavy objects are more likely to harm your cover than protect it and are likely to be shifted anyway if things get really wild out there.

Damage from flying debris:

So, your hot tub cover is secure and you can relax and enjoy the show?  Not just yet…if you’re expecting a wind storm, you will probably need to think about protecting your hot tub from other potential debris flying around.  Tree branches for example can puncture your cover or damage your hot tub cabinet.

Protection from flying debris:

If your hot tub is near or under a tree (not the best idea for this reason!) you could consider placing a piece of thin plywood on the top of the cover and strap it down to protect it during the storm.   You could do the same around any exposed sides of the cabinet that you feel are at risk.  Remember don’t use heavy objects to hold the plywood in place.  If you’re taking the plywood option, it’s important to create a buffer between the ply and the cabinet / cover with a blanket or towel otherwise your shield has left unsightly scuff marks behind.  

During the storm:

Despite your best effort’s things could still go wrong.  In the middle of a storm, the most important thing to care about is your own personal safety, not your property.  Now is the time to stay indoors – do not go outside while the storm is in progress.  A replacement hot tub cover is cheaper and easier to replace than you are!

Interested in finding out more?

Read our blog on how to look after your hot tub cover.