Pool Water Testing: How to Test Your Pool Water Chemistry



When summer hits, spending your days by the pool with family and friends is the ultimate relaxation.

But before you can jump in to cool down, you need to ensure that the water is safe to swim in.

That’s why pool water testing is vitally important, as it’s the most common and frequent maintenance that will have to be done.

Pool Water Testing: Why It Matters 

Have you ever taken a bath, let the water sit overnight, and then taken another bath the next day? How about reusing the water you washed last night’s dishes in?

Pretty nasty, right? 

Unless you have serious hygiene issues, my guess is you use clean water all the time to limit the chances of getting sick.

Unfortunately for pools, you can’t exactly swap out the water every time you use it. 

Instead, chemicals are introduced into the pool water which keep things clean and safe, so you aren’t swimming in a potential biohazard.

Of course, what type of pool you have (chlorine vs. salt) will determine the testing and treatment you give to the water. But make no mistake, staying on top of testing is something that all pool owners need to be committed to.

When You Should Be Testing 

Rest assured, testing pool water doesn’t have to be a daily occurance, but regular testing is very important. This is what will keep your water’s alkalinity, pH, and chlorine levels balanced. If these levels get out of whack, what results is a breeding ground for bacteria that can cause serious harm to your pool and your health. 

The first test you should perform will be when you open your pool, and the last test should be when you close down the pool for the year.

Over the course of pool season, testing once a week is good practice to ensure things are running smoothly. This also helps you be proactive in identifying any potential problems before they get out of hand.

However, when your pool is subjected to foreign elements, it can upset the chemistry of the water. You’ll want to perform more frequent testing in the following situations:

  • After large groups of people have used the pool
  • After it rains
  • After you’ve added water
  • After you’ve treated the water with chemicals
  • After changes in weather/temperature
  • If you notice any changes in the water’s color and/or transparency

While pool water testing can be done by yourself (and we highly suggest you learn this skill), we still recommend having your water tested by a professional when opening and closing your pool.

This will ensure your water is performing perfectly – safe for swimming in and not potentially damaging the pool. You can bring a water sample to any pool store to have this service performed. 

How to Test Your Pool Water (3 Ways) 

Testing your pool’s water is pretty simple and with a bit of practice it will become second nature. 

There’s a few different ways you can test, all of which require you to take a sample of the pool’s water.

Taking a sample is an easy, 4-step process:

  1. Position yourself away from your pool’s skimmer and return jets
  2. Using a cup, turn it upside down and plunge it elbow deep into your pool
  3. Flip the cup over so it fills up with water
  4. Scoop out the water

Now that you have your water sample, how do you test it?

1. Use Test Strips

Test strips are the easiest way to get accurate readings of your water’s chemical makeup. While you’ll most likely use them more frequently, they aren’t very expensive so you won’t be breaking the bank every time you buy a new pack.

Test strips are simple to use and give you readings for the main components: pH, alkalinity, and chlorine. Depending on the strip, it may also test for a wider range of components – things like salt, bromine, iron, and copper.

All you have to do for testing is dip the strip into your water sample. It takes about 15 seconds for the results to show. On the back of the test strip bottle will be a chart that shows the ideal colors/levels that your strip should match. This chart will also indicate what levels you have too much of, or too little of.

2. Use a Liquid Test Kit

Liquid test kits come with everything you need to balance your water’s levels. However, they can be less accurate than test strips and a bit more fussy to use. 

With this kit, you’ll use it to take 2 samples of your pool’s water (using the same 4-step method as previously described). 

The liquid test kit comes with two chemicals you must add to the water samples: OTO (orthotolidine), and phenol red. OTO measures the water’s chlorine level, while phenol red measures pH level.

After adding 4 to 5 drops of each, you can shake up the samples and watch the water change color. On either side of the water samples will be the corresponding colors you are aiming for. For this reason, you should keep a piece of white paper with the kit that can be used for an accurate representation of the colors.

3. Use a Digital Test Kit

For those that prefer to incorporate cutting edge technology into their pool testing regimen, you can invest in a digital testing kit. 

While they cost quite a bit more than test strips and liquid test kits, they’re very accurate and take the guesswork out of matching your sample color to the chart color. Those with poor eyesight would benefit greatly from this type of kit.

In addition to testing for pH, chlorine and alkalinity levels, digital test kits also have the ability to analyze a wider range of chemicals: cyanuric acid, calcium hardness, and bromine. They can also check free chlorine and combined chlorine levels.

Not all digital kits operate the same, so you’ll want to follow the instructions that the kit provides.

Alternatively: Go for In-Store Testing

If you aren’t into DIY, in-store pool water testing is a good way to get accurate readings. 

Some stores provide free water testing service, and in many cases they can help formulate a customized treatment plan. 

This ensures you will always have clean, safe, and healthy water at all times.

Testing the Basics

So, what things are you testing for, why do you need to test for them, and how do they affect your pool and anyone using it?


The pH scale runs from 0 to 14, measuring acidity and basicity. Anything under 7 is considered acidic, while anything over 8 means the water is alkaline (basic). 

To put things into perspective, fresh water has a pH level of 7, while water with a pH level of 6 is 10 times more acidic than fresh water.

The sweet spot you want to aim for to balance your pool’s pH level is 7.4 to 7.6.

Acidic pools (low pH) can cause eye and skin irritation, can corrode the pool’s mechanical system and pumps, as well as things like ladders and diving board supports.

Conversely, a high pH level (alkaline) can lead to cloudy water due to mineral deposits, damaged vinyl liners, and inactivated chlorine (meaning the chlorine won’t actually be cleaning the water). 

As the pH level can be easily thrown out of balance, it’s recommended to test for this at least once a week. If you can test daily, that’s even better. Any kit you buy will test for pH level.

Total Alkalinity

Total alkalinity is what stabilizes your pH balance, and its ideal level is between 80 and 120 ppm (parts per million). If total alkalinity falls below 80, it can cause fluctuations in the pH level. If it spikes above 120, the pH can rise, resulting in inactivated chlorine.

Balancing out your pool’s alkalinity can be done by using a buffer like cyanuric acid, which has a higher pH level. This, in turn, gives the pool an elevated pH level, which helps counteract any contaminants (which are low pH) that may enter the water.


Chlorine is sanitizer for your pool water. It keeps your pool clean and safe by killing off any contaminants in the water. 

Test strip kits will test for this by color code matching, and liquid test kits will test for it when you add the provided OTO to your water sample. 

The ideal range for chlorine falls between 2.0 and 4.0 ppm.

If you need to raise the chlorine level, you can add chlorine tablets. If you give your pool an accidental overdose of chlorine, simply wait it out. Contaminants in the water, newly formed bacterias, and the sun’s UV rays will eventually deconstruct the chlorine to a safe-for-swimming level.

Cyanuric Acid

Cyanuric acid (aka CYA), is a weak acid that attaches itself to chlorine molecules and reduces chlorine degradation due to sunlight. It’s known as pool stabilizer, or pool conditioner, and needs to be at a level of 50 ppm for optimal performance. Any higher and the chlorine becomes inefficient at sanitizing.

Also of note, most chlorine tablets include cyanuric acid, so you will have to be careful of how high your level is at so you don’t overdo it. Otherwise you will have to switch to non-CYA chlorine tablets, and may need to drain and refill your pool to dilute CYA levels!

Specialized Tests

Aside from pH, alkalinity, and chlorine, there are a few other components you can test your pool’s water for. Not all testing strips/kits do these specialized tests, so make sure you’re purchasing a testing kit that can.

Calcium Hardness

Calcium hardness is better known as hard water, and can wreak havoc by leaving mineral deposits on your pool, your filter, and plumbing system. Lowering calcium hardness can be done with various chemicals, but softening the water too much can introduce corrosive elements to your pool’s water as well. 

So, you will need to balance the water.

Vinyl liner pools should aim for 175 to 225 ppm, and concrete pools should be between 200 and 275 ppm. 

Metals (Copper & Iron)

Lower pH levels can lead to metals like copper and iron being introduced into the water. If you notice your pool slowly turning brown, or rust stains building up, you should test immediately. Otherwise, monthly testing for metals is perfectly good practice.


Testing for salt is reserved for those with – you guessed it – a salt water pool! The issues around salt is that too much will lead to overproduction by the salt chlorine generator, while low levels won’t be enough to keep the pool sanitized.

Testing your salt water pool can be performed monthly, although with frequent use you will most likely want to test it more often.


Phosphates are a natural occurrence in pools. While they are a food source for algae, lowering the phosphates isn’t necessary. Instead, you’ll want to avoid algae from forming in the first place by controlling it with algaecide and keeping your pool water well-balanced.

Pool Water Testing: Simplified!

Testing your pool’s water isn’t a hard job, but it does require you to understand a little bit about how to keep your water clean and healthy when your pool is in use. 

With plenty of test kit options available, you shouldn’t have any problems keeping your pool water in peak condition, and you can worry less while spending more time enjoying your pool. 

Categories: Pool Care, Pool Chemistry