What Chemicals Should I Put in My Hot Tub First?
If you've recently purchased a hot tub or are refilling it with fresh water, knowing which chemicals to add first is essential for maintaining clean, clear and safe water. Adding the wrong chemicals in the wrong order can make balancing your water more difficult and potentially affect your hot tub's equipment.
When starting a new hot tub, you should generally balance your total alkalinity first, followed by pH, calcium hardness and finally your chosen sanitiser. Here's a step-by-step guide to the chemicals you need, what they do and when to add them.
Step 1: Get Your Hot Tub Chemical Starter Kit
If you're new to hot tub ownership, the easiest way to get started is with a dedicated hot tub chemical starter kit. These kits bring together several of the essential products needed to balance and sanitise your water, saving you from having to purchase everything individually.
A typical hot tub chemical starter kit includes products for adjusting alkalinity and pH, sanitising the water and maintaining overall water quality. Depending on the kit selected, you may also receive additional treatments and accessories.
Before adding anything, fill your hot tub according to the manufacturer's instructions, ensure the circulation system is operating correctly and test your fresh water. Your initial readings will determine which chemicals you actually need.
A convenient selection of essential hot tub chemicals to help you get started with water balancing and sanitisation.
Shop Chemical Starter KitsStep 2: Adjust Your Total Alkalinity First
Total alkalinity is one of the most important measurements when setting up your hot tub. It helps stabilise the water's pH level, preventing it from fluctuating too easily.
If your total alkalinity is too low, your pH can become unstable and difficult to control. If it is too high, you may experience persistently high pH readings, cloudy water and potential scale formation.
For many domestic hot tubs, a typical total alkalinity target is between 80 and 120 ppm (parts per million). Always check your hot tub manufacturer's recommended range.
Test your water before adding anything. If your reading is below the recommended range, use a total alkalinity increaser to gradually raise it. Allow the water to circulate and retest before moving on to the next stage.
Designed to increase total alkalinity and help stabilise pH levels in your hot tub.
Shop Alkalinity IncreaserStep 3: Balance Your Hot Tub's pH Level
Once your total alkalinity is within the recommended range, the next step is to check and adjust your hot tub's pH level.
pH measures how acidic or alkaline your water is. Keeping it balanced is important for bather comfort, sanitiser performance and protecting your hot tub's internal components.
A typical recommended pH range for a hot tub is between 7.2 and 7.8, although you should always follow your spa manufacturer's guidance.
There are two main products you may need:
- pH Plus: Used when your water is too acidic and the pH reading is too low.
- pH Minus: Used when your water is too alkaline and the pH reading is too high.
Only use the product required to correct your test result. Add the recommended dose, allow the water to circulate and retest before making further adjustments.
Pure-Spa pH Plus
Raises the pH level of your hot tub water when readings are too low.
Shop pH PlusPure-Spa pH Minus
Lowers the pH level when your hot tub water is too alkaline.
Shop pH MinusStep 4: Check and Adjust Your Water Hardness
Calcium hardness measures the amount of dissolved calcium in your hot tub water. It is another important part of water balancing and is often overlooked by new hot tub owners.
If calcium hardness is too low, the water can become aggressive towards certain spa components and surfaces. If it is too high, calcium deposits and limescale can develop on the heater, pipework and other internal components.
Test your water hardness and compare the result with your hot tub manufacturer's recommended range. If your calcium hardness is too low, use a hardness increaser to bring it towards the required level.
Many domestic hot tubs use a typical calcium hardness target of around 150-250 ppm, although requirements vary between manufacturers and water treatment systems.
Helps increase calcium hardness levels when your hot tub water is too soft.
Shop Hardness IncreaserStep 5: Add Your Hot Tub Sanitiser - Chlorine or Bromine
Once your water balance has been adjusted, you need to introduce a sanitiser. This is one of the most important stages of hot tub maintenance, as sanitiser helps kill harmful bacteria and other microorganisms that can enter the water.
There are two main sanitising systems used in domestic hot tubs: chlorine and bromine. Both are effective when used correctly, but you should choose one sanitising system and follow it consistently rather than combining the two.
Option 1: Chlorine Sanitiser
Chlorine is a popular choice for hot tub owners because it is effective, readily available and relatively straightforward to maintain. It helps disinfect the water and control bacteria introduced through everyday use.
You can use chlorine granules for dosing and adjusting your chlorine levels, or chlorine tablets for a more gradual release of sanitiser when used in a suitable dispenser.
Pure-Spa Chlorine Granules
A fast-dissolving chlorine sanitiser for treating and maintaining hot tub water.
Shop Chlorine GranulesPure-Spa Chlorine Tablets
20g chlorine tablets for maintaining sanitiser levels when used in a suitable floating dispenser or approved dosing system.
Shop Chlorine TabletsOption 2: Bromine Sanitiser
Bromine is another popular sanitising option for hot tubs. It is particularly well suited to warmer water and is often preferred by owners who want an alternative to chlorine.
Like chlorine, bromine helps control bacteria and maintain hygienic water conditions. You can use bromine tablets or bromine-infused granules, depending on your preferred dosing method and the requirements of your spa.
Pure-Spa Bromine Tablets
19g bromine tablets for maintaining bromine levels in your hot tub using a suitable dosing system.
Shop Bromine TabletsPure-Spa Bromine-Infused Granules
An alternative bromine treatment option for maintaining sanitiser levels in your hot tub.
Shop Bromine GranulesNever mix chlorine and bromine products together or introduce one sanitising system into water containing the other. Always follow the product instructions and ensure your chosen sanitiser is compatible with your hot tub and any existing treatment system.
Step 6: Consider Multifunctional Hot Tub Tablets
If you prefer a more convenient approach to routine hot tub sanitisation, multifunctional chlorine tablets may be worth considering.
These tablets combine several water treatment functions into one product, typically including chlorine sanitiser, algicide and clarifier. This helps simplify ongoing water care by combining multiple treatments in a single tablet.
Multifunctional tablets are chlorine-based, so they should only be used as part of a compatible chlorine sanitising programme. They do not replace the need to test and balance your alkalinity, pH and calcium hardness independently.
A convenient multi-action chlorine treatment combining sanitiser, algicide and clarifier.
Shop Multifunctional TabletsStep 7: Use a Floating Spa Dispenser for Tablets
If you choose chlorine or bromine tablets, a floating spa dispenser can make maintaining your sanitiser levels more convenient.
A floating dispenser holds compatible sanitising tablets and gradually releases treatment into the water as it circulates. The adjustable dispenser allows you to control the tablet exposure, helping maintain sanitiser levels between regular water tests.
Always use a dispenser suitable for your chosen chemical and follow the manufacturer's dosing instructions. Do not place tablets directly into the hot tub water, filter compartment or skimmer unless your spa manufacturer and chemical instructions specifically permit it.
A practical accessory for dispensing compatible chlorine or bromine tablets into your hot tub.
Shop Floating Spa DispensersFinal Checks: When Can You Use Your Hot Tub?
Once you've added the necessary chemicals, don't rush straight into your first soak. Give the water sufficient time to circulate and allow each treatment to work according to its product instructions.
Before using your hot tub, test the water again to confirm that the pH and sanitiser levels are within the recommended ranges. Check the water is clear and that all chemical readings are suitable for bathing.
Remember that adding chemicals is only the beginning of your hot tub maintenance routine. Regular testing, filtration and ongoing sanitisation are essential for keeping your water clean and safe.
- Always read the manufacturer's instructions before using any chemical.
- Never mix different chemicals together, particularly chlorine and bromine products.
- Wear suitable protective gloves and eye protection when handling chemicals.
- Only pre-dissolve chemicals when the product instructions require or permit it. Always add chemicals to water, never water to chemicals.
- Allow sufficient circulation time between chemical additions.
- Keep chemical containers sealed and stored in a cool, dry and secure location, away from children and pets.
- Never use your hot tub until the chemical readings are within the recommended bathing ranges.
Frequently Asked Questions About Hot Tub Chemicals
What chemicals should I put in my hot tub first?
When filling a hot tub with fresh water, start by testing the water. Adjust total alkalinity first, followed by pH and calcium hardness if required. Once the water is balanced, introduce your chosen sanitiser, either chlorine or bromine. Allow the water to circulate and retest before using the hot tub.
Should I add chlorine or pH balancer first?
Generally, you should balance your water before adding chlorine. Start by adjusting total alkalinity, then correct your pH level. Once these readings are within the recommended ranges, add your chlorine sanitiser according to the product instructions.
Do I need chlorine and bromine in my hot tub?
No. You should choose either a chlorine-based or bromine-based sanitising system. Both are effective at disinfecting hot tub water when used correctly, but they should not be mixed together. Choose the system recommended for your spa and maintain it consistently.
How much chlorine should I put in my hot tub for the first time?
The amount of chlorine required depends on your hot tub's water capacity, the current sanitiser reading and the concentration of the product being used. Always test your water and follow the dosing instructions on your chlorine product rather than guessing. Retest after treatment to confirm the correct level has been achieved.
How long should I wait after adding hot tub chemicals before getting in?
Waiting times vary depending on the chemical and dosage used. Allow the water to circulate for the period stated on the product instructions and retest the water before bathing. Do not use your hot tub until the sanitiser and pH readings are within the recommended bathing ranges.
What is the correct pH level for a hot tub?
A typical recommended pH range for domestic hot tubs is 7.2 to 7.8. Keeping pH within the correct range helps maintain sanitiser effectiveness, improve bather comfort and protect your hot tub's internal components. Always check your manufacturer's recommendations.
What should my hot tub alkalinity be?
Many hot tub manufacturers recommend a total alkalinity level between 80 and 120 ppm. Total alkalinity helps stabilise pH and prevents it from fluctuating excessively. Use a suitable alkalinity increaser if your test results are below the recommended range.
Do I need a hot tub chemical starter kit?
A starter kit is a convenient option for new hot tub owners because it combines several essential water treatment products in one purchase. It can save you from buying individual chemicals separately and provides a useful starting point for establishing your water maintenance routine. Always check which products are included in the kit you select.
Can I use multifunctional chlorine tablets in my hot tub?
Multifunctional chlorine tablets can be used in compatible hot tub systems when the product is specifically suitable for spa use. These products combine chlorine sanitiser with additional treatments such as algicide and clarifier. They do not replace the need to balance your pH, alkalinity and water hardness.
How often should I test my hot tub water?
Test your hot tub water regularly, ideally before each use, and more frequently during periods of heavy use. Check your pH and sanitiser levels to ensure they remain within the recommended ranges. Total alkalinity and calcium hardness should also be checked periodically and whenever you refill your hot tub.
Find Everything You Need for Hot Tub Water Care at Hydrospares
Getting your hot tub chemicals right from the beginning makes ongoing maintenance much easier. From alkalinity increasers and pH balancers to chlorine, bromine and multifunctional treatments, Hydrospares stocks a range of Pure-Spa water care products to help you maintain clean, balanced hot tub water.
Explore our range of hot tub chemicals and water treatment products to find everything you need to get your spa started.