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Hot Tub Water Testing for Dummies: Ultimate Guide for 2023

Are you one of those people that love to relax in a hot tub after a long day at work? If so, you should know about hot tub water testing and why it’s the most important part of your hot tub maintenance routine.  

Keeping the chemicals you use in your spa balanced is essential to prevent common issues like cloudy water and algae, avoiding health risks such as nasty rashes and protecting the spa’s components against damage. You’d also answer the question we get asked a lot which is are hot tubs safe?

Knowing how to test your water quality and adding the right amount of chemicals means it’s enjoyable for everyone.

In this blog post, we’ll discuss the best ways to test your hot tub water, what all those colours on the testing strip mean and what to do if the water quality is poor. So, if you’re ready to learn more about water tests’ importance in keeping your portable spa safe, keep reading!

How To Test Hot Tub Water For Bacteria – Complete Guide

a test strip and container with instructions on how to use

The good news is that testing your hot tub water is a straightforward job that takes seconds, so let’s dive in and find out all about how these testing kits work once in the hot tub and when to test hot tub water.

What to use – Strips vs Liquid?

The two types of test kits most used by the home hot tub owner are liquid testing kits and test strips. Basically, both do the same job, but many owners find a test strip gives a more accurate reading and of course, by their very nature, they are simpler to use. 

What about a digital hot tub water tester? 

A digital test kit is a piece of equipment that can measure various water parameters and is often used to test the water in swimming pools. Of course, a quality digital test kit will cost more than simple strips (some are upwards of £100) and being perfectly honest; we’ve seen mixed reviews when people test the water.

However, they do give you peace of mind as they can be left in the water so that you can be warned of any discrepancies with chemical levels immediately.

Taking the Sample

Whether you are using a strip or liquid test on your hot tub, you should follow the instructions steps and use water from the centre of the spa or hot tub and ensure the jets aren’t on, as the water must be as settled as possible to get the best results and provide a great spa experience in the future.

How To Test Hot Tub Water With Strips

The strip will have various pads for different results and an empty length at the bottom for you to hold. You can either collect some water in a plastic container from hot tubs or dip the testing strips directly in the hot tub water. 

After dipping the strip into the water sample, wait the required time, then match the colours against the corresponding chart on the bottle. 

Liquid Test Kits

someone pouring blue liquid from one glass to another

If you use this method, make sure the kit includes phenol red to test PH and orthotolidine (OTO) to test Chlorine.

  1. Collect a small sample of hot tub water from the centre of the Jacuzzi in the container or test tube provided 
  2. Add the manufacturer’s recommended number of drops of phenol red to the pH side of the container and do the same for the OTO
  3. Hold the container against a white background like a sheet of paper and compare the colour of the hot tub water with the chart provided. 

What Are You Testing the Hot Tub Water For?

Some hot tub test kits measure for specific things like Chlorine or salt levels, but the most common are the multi-function testing strips that measure multiple parameters simultaneously. Below are some of the things you will find on the coloured strips. 

PH levels

an image of a PH scale

Having a balanced PH level is one of the most important things for your hot tub water’s quality. The perfect result you want to see on the test strip here is between 7.2 – 7.8 for your hot tub.

If the reading is below 7.2, your hot tub water is too acidic; this can cause skin irritation and red eyes and will also result in the sanitiser becoming less effective. Chlorine tablets and rainwater can cause low PH levels. 

If you encounter a high PH level of 7.8 or above, the water in the tub is too alkaline; this too can cause skin irritation as well as a build-up of scale and even make the water cloudy. An alkaline PH level is quite common as it can be caused by detergents left in the water from bathing costumes, make-up, body oils and debris.

To test your PH, simply dip the strip into the hot tub’s water and wait the recommended time, which you will find on the instructions; they all differ, so do remember to check. 

After a few seconds, hold the strip to the manufacturer’s chart, where the colours will indicate if the PH level is correct or needs to be adjusted. 

Total Alkalinity

Close related to the all-important PH level is total alkalinity. You need to get this one spot on; otherwise, your PH level will constantly be going up and down in the tub. Basically, it is the level of dissolved alkaline substances found in the water.

The Total Alkalinity measured should be between 80-120 ppm (parts per million). Anything outside this range will mean your PH levels will be virtually impossible to maintain and your hot tub water quality won’t be great. 

Again, you need to dip the test strip into your Jacuzzi, holding it about 6 inches below the surface for the manufacturer’s recommended time. Wait a few more seconds after taking the test out and hold it against the corresponding chart to see the result. If the test isn’t within the correct range, this will need addressing before tackling the PH level.


It’s crucial to test your hot tub water for calcium hardness as this can be one of the most damaging elements for your expensive hot tub. If the Calcium levels are too high, you will notice scale starting to build up, or your water may become cloudy. Too much of the stuff can also result in dry, itchy skin.

Many areas of the UK are hard water areas and the only way to reduce the amount of calcium in your hot tub water is by using a water softener when filling the tub. Intex actually has a dedicated hard water treatment system built into their spas which could be an option if you live in one of these areas.

If your calcium level is too low, the water and surfaces of your blow-up spa may feel slimy and in this case, you can add a calcium booster. Here is an in-depth article about why is my hot tub slippery.


hot tub chemicals being poured into a hot tub

Another thing you need to test your hot tub water for is Chlorine. Chlorine keeps the water hygienic and safe to use by preventing the growth of bacteria, microorganisms and germs. 

Total Chlorine levels

The total Chlorine measurement on a test strip should show between 1.5 – 3 ppm (parts per million). 

Free Chlorine

This is the amount of chlorine left in the water after it has done the job of eliminating the nasties, this Chlorine is still active and the reading should fall between 1 -3 ppm but should be above the TC level. 

Cyanuric acid

This acid is part of your Chlorine Stabiliser. It stops the Chlorine from disintegrating in sunlight and becoming incapable of keeping the water clean 

The proper amount of CYA  in your hot tub water should be between 30 and 50 ppm (parts per million) for adequate protection. 


white powder in a scoop and three tablets stacked on top of eachother

Some hot tub owners prefer to use Bromine instead of Chlorine to sanitise their spa and if this is the case, you will need to ensure you purchase the correct testing strips or an all-in-one testing kit that includes Bromine results. 

The recommended total Bromine level in your hot tub is between 3-5 ppm 

Total Dissolved Solids (TDS).

Over time, debris, minerals, body oils etc., saturate the water. Even if you add enough sanitiser, there comes the point when it will stop working. This will cause your water to become cloudy, you may suffer from foam and it will be extremely challenging to balance the PH level.

Not all testing strips have this on their charts, so check before you purchase a test.

Hot Tub Water Quality

Issue Solution 
Low PH level, Normal TAYou will need to add a pH increaser that won’t affect the TA level.
Low PH level, High TAFirst, you will need to lower the TA by using a decreaser; then you can address the PH with an increaser that doesn’t affect the TA.  
Low PH level, Low TAUse an increaser that will raise both levels
Normal PH, Low TAIn this situation, you will need to use an alkaline increaser to raise the TA to the correct level.
Normal PH, High TAThe TA level needs to be lowered with a PH decreaser 
High PH, High TAA PH decreaser needs to be added to reduce both levels 
High PH, Normal TABring the PH level to within range by using a PH decreaser 
High PH, Low TAFirst lower the PH level then use an alkaline increaser to up the TA levels. 
Chlorine less than 3ppm Use a Chlorine shock treatment to restore balance
Too much Chlorine The Chlorine will disperse naturally over a few days, but if you want to use the spa quickly, you can add a Chlorine neutraliser.

Why is Regular Water Testing so Important?

It’s essential to test hot tub water before every use to ensure it’s hygienic and safe for use, it means your keeping the hot tub clean and make the appropriate chemical adjustments to the hot tub if needed. The filtration system in your hot tub does a good job of maintaining clean hot tub water, but several outside factors can cause fluctuations in the chemistry. 

This can cause damage to the pipes and hot tub components, result in issues like foamy or cloudy hot tub water and even make you prone to developing skin irritations or more hot tub bacteria symptoms like Legionnaires disease. 


How often do you need to test hot tub water?

Do hot tub water test strips expire? 

Does bromine show up on chlorine test strips? 

How accurate are hot tub test strips?

Last Word

couple sat in a hot tub cuddling

As we’ve talked about in the information above, water testing for hot tubs is a vital part of their upkeep, and a lot of people don’t know that, not just for hygiene reasons but to keep everything in good working order. 

Testing strips are one of the most simple, effective, and inexpensive ways to do this. You can either buy strips designed for a specific purpose, such as test strips for Chlorine. Or, as many hot tub owners do, buy test strips that test for several things at once, such as total hardness, total alkalinity or TA levels and Chlorine amounts. 

Instructions will vary depending on the chemical kits you buy, so always read through before using and wear gloves when handling inflatable hot tub chemicals

Regularly testing your hot tub water isn’t difficult and shouldn’t just be confined to when there’s an issue or more people have been using the spa. It’s something that should be done as part of your regular maintenance routine at least once a week to keep your hot tub clean and prevent issues from occurring. 

John Devlin

Hello, Welcome to my website. I’m John, and I created the InflatableHotTubGuide while researching these spas nearly a decade ago. Since its creation, the site has become the leading UK resource for many models. As a passionate hot tub user, I love to test and explore all the latest machines this industry keeps creating. I hope you find our content helpful.