Frequently Asked Questions

Hot Tub Water – Temperature

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!

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.

Check out our additional FAQ for more information

If you have a health condition you must consult your doctor before using a hot tub.

This includes, but is not limited too chronic illnesses or conditions such as a heart condition, high blood pressure and diabetes.  This is because there is an increased danger of developing several conditions related to hyperthermia. This means that you have an excessively high body temperature. The dangers range from mild to seriously life threatening.  These may include Heat Rash, Heat Cramps, Heat Stroke and Heat Exhaustion.

If you are, or may be pregnant, please see our FAQ for separate advice.

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.

Children under 4 years of age should not be allowed to use a spa. (Ref. HSG 282 published by the UK Health & Safety Executive.)

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.

Lowering your hot tub’s heat setting when you’re not using it for longer periods may cut your energy costs. But 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.

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.

A floating heat retention cover and a good quality, good condition hot tub cover will help to significantly reduce energy costs.

Yes!  Dropping the temperature of your hot tub is a great idea. This can help you avoid a high energy bill when you return. 

A lower temperature will also reduce the amount of sanitiser used up while you are away.  Most hot tubs have an economy or holiday setting that will maintain much lower water temperatures.  Just beware if ambient temperatures are around freezing. By setting the spa too low or even turning the heater off, you risk burst pipes and potentially some expensive damage to pumps and other hardware.

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.

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.

Chlorine tablets are made from Trichloroisocyanuric acid. This is more acidic than the chemical used in chlorine granules. For this reason, using chlorine tablets will invalidate the manufacturers warranty on some spas. Be sure to check terms and conditions before using Chlorine Tablets in your hot tub.

The benefit of using chlorine granules is that they are quick to dissolve and relatively pH neutral.

This also 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.

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.

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

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.

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

Yep, a little maths is required!

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.

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.

The keys to maintaining safe and healthy hot tub water while using lower levels of chlorine as a sanitiser are maintaining water balance and eliminating biofilm.

Keep pH levels balanced – ideally close to pH 7.2
This is because as pH levels rise, chlorine becomes less effective.  At a pH of 8, over half of chlorine added to your hot tub water is ineffective.  Chlorine is more effective at a lower pH.  At a pH of 7.2 chlorine rises to 90% effectiveness – actively available to kill algae and bacteria.

Eliminate bio-film.  Biofilm is a type of slime that can form and provide a safe shelter for bacteria allowing them to breed virtually unmolested by chlorine or any other sanitiser.  AquaFinesse is a product that breaks this shelter down allowing smaller amounts of chlorine to be more effective.

A strong smell of chlorine is often mistaken for too much chlorine in the water. In fact it is an indication that the chlorine has been “used” up.

When chlorine combines with organic waste (body fluids, dead skin etc) it produces a compound called chloramine. This gives off a strong chlorine odour.

Disinfection byproducts such as chloramines can be irritating, to your skin, eyes and respiratory system. A shock treatment will breakdown chloramine so it can be easily removed from the water, “freeing up” your chlorine to work more effectively.

Many people think they are allergic or intolerant to chlorine, but 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.

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.

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

In a commercial environment, at least daily. In a home setting at least 2-3 times a week is a good guideline.

How often you need to check pH levels depends on how balanced and stable your water chemistry is.

If this sounds wasteful or expensive in time and test strips, consider the damaging effects of unbalanced water, both to you and your hot tub!

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 also potentially:

• Cause a 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
• Make Chlorine / bromine sanitiser much less effective and you will need to use more to get the same effect
• Cause cloudy water and a gritty feel on hot tub surfaces

The product you need is called pH decreaser, pH reducer or pH minus / pH –

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

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.

The product you need is called pH increaser, pH raiser or pH plus / pH +

The most common pH raiser products available to treat low pH in hot tubs contain the active ingredient sodium bicarbonate. Sodium bicarbonate is effective at increasing both pH and Total Alkalinity (TA).

You can, but we don’t recommend it, and we don’t supply Muriatic Acid at Castle Hot Tubs.

Although Muriatic acid provides an alternative way to decrease both pH and TA, it is an extremely caustic chemical. It must be stored safely and you must use protective glasses and chemical-resistant gloves along with a great deal of caution when working with it! You really don’t want that burning your skin.

No, you cannot use Cyanuric Acid to lower pH levels in your water.

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.

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.

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.

Adjusting the Total Alkalinity is likely to help.

Total Alkalinity 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.

Bromine is slightly more effective in an unstable pH environment.

But this isn’t really a basis for choosing which sanitiser to use in your hot tub. Achieving a balanced pH water is a necessity, whichever sanitiser you use.

The easiest option might be to drain your spa and start over.

This might be your go-to advice if you find yourself chasing high and low pH in your hot tub / spa water. 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.

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.

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.

To ensure that your spa water is safe after shock dosing, ensure that chlorine levels have dropped below 5ppm before allowing bathers back into the 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.

Non-chlorine shock helps the chlorine already in your hot tub work better by oxidising the water and creating “free chlorine” – this is what is needed to kill bacteria.

Non-chlorine shock doesn’t contain chlorine itself, and does not disinfect the water.

For those using bromine as a sanitiser, Non-chlorine shock will also activate bromine, helping it work more effectively.

If you use bromine as a sanitiser you must only use non-chlorine shock. If you use chlorine as a sanitiser, you can use either chlorine or 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.

There are a number of different reasons requiring you to shock dose your hot tub. Check out our list below:

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

Do not allow anyone to bathe while shock dosing your hot tub water.

• 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.
• 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.

Shock dosing the water will help to remove organic compounds and assist in clarifying and cleaning the water.

Us humans carry organic compounds on our skin, such as oils, cosmetics, lotions and dead skin and sweat. This can quickly accumulate in hot tub water and can cause it to become cloudy.

Maintaining regular and adequate sanitiser levels, chemical filter cleaning and shock dosing, particularly after heavy use or at the first sign of cloudy water will help restore water clarity

A strong chlorine odour is often mistaken for too much chlorine but is in fact an indication that the chlorine has been “used” up.

When chlorine combines with organic waste (body fluids, dead skin etc) it produces a compound called chloramine. This gives off a strong chlorine odour.

A shock treatment will break down chloramine so it can be easily removed from the water, “freeing up” your chlorine to work more effectively.

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

For example, Sykes reported the following benefits experienced by holiday let properties with hot tubs:

• Boosted occupancy rates
• Raised property profile on web searches
• Increased rental charges
• Increased guest satisfaction
• Improved re-booking rates

Installing a hot tub in your holiday let is a huge win.

For most holiday let owner / operators, the level of involvement and maintenance, coupled with safety concerns makes wood-burning hot tubs unfeasible.

The reality is that wood-burning hot tubs are also likely to provide a much less enjoyable experience for your guests than an electrically heated tub. A wood-burning hot tub can only offer heated water. No Jets or Pumps. No hydrotherapy. A relaxing soak is nice, a soak and a massage is nicer, in our opinion!

The complications of operating and maintaining a wood-fired hot tub include:

The stove will need clearing and resetting after each use. Will your guests do this, or will you?

A wood-burning hot tub typically takes around 3 hours to reach operating temperature. Will your guests want the hassle of building and maintaining the fire before use?

Serious risk of over-heating:

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.

No doubt, a wood burning stove heating a hot tub looks gorgeous – but is it safe in a holiday let setting if your guests have children?

Download the latest guidelines, from the Health & Safety executive.

As a very brief summary as a minimum you must:

• Have a hot tub with 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

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At Castle Hot Tubs, we are committed to providing you with a friendly and efficient service.  We acknowledge that sometimes things do not go according to plan.  If this is the case with your order, take a look through our returns and refunds policy, then contact our friendly customer services team at: info@castlehottubs.co.uk and we will do our best to help.

Delays:

If shipping of a product is delayed or prevented due to circumstances beyond our control (for example – warehouse shortages, import delays, or high demand) we will make every effort to keep you informed of the progress of your items.  Please note that our same day dispatch service is not a guarantee of next day delivery.

Non-Delivery:

All claims for compensation for non-delivery must be received Castle Hot Tubs in writing within 30 days from the date of dispatch of the goods.  Contact our customer services team by email: info@castlehottubs.co.uk with your order / invoice details and any supporting information you can supply regarding your claim.  Castle Hot Tubs may make such investigations as it deems necessary to satisfy themselves of the validity of any claim and this may take a reasonable amount of time.  Any additional information requested to substantiate a claim must be made available to Castle Hot Tubs within 21 days of request.  If the information requested is not received within this timescale, Castle Hot Tubs reserve the right to close the claim without any compensation due.

Returns of Unwanted Items:

If you wish to return any unwanted items to us you have the right to do so within 14 days of purchase, so long as they are unopened (in their original packaging) and in fully saleable condition. Bespoke items such as Hot Tub and Swimming Pool covers are non-refundable and cannot be returned under this policy as they are custom made.  We are unable to accept unwanted items that are returned more than 14 days after purchase.

How to return unwanted items:

Contact our customer services team by email: info@castlehottubs.co.uk stating the item(s) to be returned, the reason for return and our order / invoice reference number.

To return your items, you should securely mail them, in the original packaging material if possible, to: Returns Dept, Castle Hot tubs, Delfryn, Hayscastle, Haverfordwest, SA62 5QG, United Kingdom.

You will be responsible for paying for your own shipping costs when returning an unwanted item. Shipping costs are non-refundable.

Returned items should be sent to us via a trackable delivery service – we cannot provide a refund for items which have not been received by us and for which there is no proof of postage.

Refunds:

Once your return is received and inspected, we will send you an email to notify you that we have received your returned item. We will also notify you of the approval or rejection of your refund.

If you are approved, then your refund will be processed, and a credit will automatically be applied to your credit card or original method of payment, within 3 working days.

High Value Items:

If you are return shipping an item with a value of more than £50 we recommend that you purchase additional shipping insurance. We are not able to provide refunds on items that are returned to us in a damaged condition.

Late or missing refunds:

If you have been notified by us that your refund request has been approved, but you haven’t received a refund yet, please ensure that you have allowed 3 working days from receiving our notification to allow your payment to be processed.

If you still have not received your refund after this time, please contact our customer services team by email at:  info@castlehottubs.co.uk

Incorrect or Damaged Orders:

Castle Hot Tubs do everything they can to deliver a professional friendly service and ensure your order arrives promptly and in perfect condition. If a parcel has been clearly damaged in transit, we ask that you refuse to accept the delivery from the courier.  If upon opening a parcel you find that you have received an incorrect or defective / damaged product, please notify our customer services team by email at: info@castlehottubs.co.uk within 14 days of delivery with your order / invoice reference number and attach photographs of the item(s).  We may ask you to return or dispose of the item if it is damaged and unsafe to return to us, please wait for us to advise you how to proceed.  We reserve the right to refund, exchange the item, or close the claim without any compensation due depending on the circumstances of the claim.

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