Pool Care Pool Water Chemistry

Pool Water Testing 101 (Everything You Must Know)


Is it time to reopen your swimming pool after a long winter season? Or are you getting ready for a relaxing evening? Or are you planning to hold a pool party for your friends? Whichever the reason, you have to get your swimming pool ready for the action. How will you do that? The secret is Pool Water Testing.

When you do the pool water testing, will you know the chemical levels? Or will you know the desirable substances in it? Or will you know the amount or the type of chemicals to add to the water to create a clean, safe swimming pool?

Well! You don’t. You have first to learn how to test and when to test it. And you know what, among the many pool maintenance tasks you have to perform during your pool’s life, pool water testing is the task you have to do more and frequently. That’s why you’ve to know how to pool test your pool water right.

If you want to know more, this is your article – it has everything you need to test your pool water, from start to the end.

Why is Pool Water Testing Necessary?

Pool water testing is regular maintenance needed in maintaining crystal clear and algae-free water. It also helps maintain good chemical balance, thus preventing injuries to the swimmers and damages to the pool itself and equipment.

If you didn’t know, imbalanced water is responsible for eye irritation, skin rashes, and hair discoloration. Can you imagine?

If you did a test before, you might have tested for things like chlorine levels, alkalinity, and pH balance. But did you check the salt levels if you’re using saltwater?

What about potential metal contaminants such as iron, calcium, copper, or even phosphates. Not testing everything leaves your pool vulnerable to the cloudy or foamy pool and potential damage.

What are Normal Pool Chemical Levels?

During routine pool water testing, you will need to test the main chemicals -; water pH, calcium hardness, alkalinity, and sanitizer levels (chlorine or salt).

In other cases, you might want to check the levels of stabilizers and metals. Below are recommended levels for a balanced swimming pool.

      Test                            Range

Water pH                             7.2 – 7.6

Total Alkalinity                  120 – 150 ppm

Free Chlorine                     1 – 3 ppm

Calcium Hardness            175 – 225 ppm (for Vinyl Pools)

Calcium Hardness            200 – 250 ppm (for Concrete Pools)

Copper                                0 ppm

Iron                                     0 ppm

**Free Bromine                3 – 5 ppm

**CYA                                 30 – 50 ppm

What Methods are used in Pool Water Testing?

Even though the whole pool water testing thing sounds like a complicated process, it’s not. The fact is, it’s a straightforward thing and with few testing methods. You can choose between:

  • Use test strips – the quickest and easiest
  • Use a liquid test kit– considered more comprehensive
  • Take a water sample to a local pool store – the most thorough and more accurate

The process might be simple, but there is one thing you should know, the water sample is the most crucial part in getting accurate water testing results.

How to Take a Pool Water Sample

Among the crucial factors to consider while taking a pool test water sample is where to take it and how to take it. The best place to draw the water sample from the absolute pool middle. Here are the steps to take:

  1. Get a clean 1-liter plastic container. Avoid using a glass jar or a chemical bottle. Hold it upside down with its opening facing the pool floor.
  2. Draw the water sample 18-inches below the water surface or an elbow deep. Make sure it’s away from the return and skimmers.


  • Make sure your pool water has been circulating for at least 48 hours continuously. During the winter season, pool chemicals like the stabilizer, calcium, and salt tend to settle in the bottom.
  • When you take the sample to a local pool store, they might ask you to provide your water clarity (clear or cloudy), water temperature, and the algae color, which will be either black, green, or mustard.
  • Avoid storing your water exposed to the sun or hot car for an extended time.

How to Use Test Strips

The use of test strips is regarded as the quickest and easiest. The method is also known to be more accurate compared to liquid test kits.

It’s challenging to match the colors using chemical drops. Another thing, test strips are less expensive compared to liquid kits, but you will run out fast.

You should, though, never use test strips when reopening your swimming. Here is how you can use them to test your pool water:

  • Take the water sample you collected and dip a test strip in and out as quickly as possible. You don’t need to soak it.
  • Once it’s out, hold it in the air without shaking for about 15 seconds.
  • Compare the strip color by matching it with the colors on the guide on the strip packaging.
  • Once you have your conclusion, you can adjust your pool water chemicals accordingly.

Most of the strips for testing water chemistry are general types designed to check the primary pool chemicals such as water pH, chlorine, and alkalinity.

If you want to test metals such as copper, iron, and other compounds, you will want to get test strips designed explicitly for those tests.

How to Use a Liquid Test Kit

If you need to perform regular pool maintenance testing, then a liquid test is the best option as it’s considered more comprehensive.

Before using it, ensure it contains orthotolidine (OTO) and phenol red for testing chlorine and water pH. Here are the steps to follow when using a liquid test kit:

  • Pick the water sample you collected and pour it into the test kit collector. You can also collect t directly from your pool using the collector.
  • Pour the recommended phenol red drops on the side designated to test water pH, and OTO drops on the other side, meant for testing chlorine.
  • Find a white background and hold the collector up against it. Compare the watercolors to the given scales printed on the collector.
  • The while background helps see the fainter colors that show the low levels. You can even use white printer paper.
  • Note: the redder the watercolor, the higher the water pH. The yellower the watercolor, the higher the chlorine levels in the water.

Taking Pool Water Sample for Professional Water Testing

If your best option is to take your pool water sample to a local store for testing, get the sample the same way. The best part about this approach is you will get accurate results and a professional opinion on what to do.

The other two methods might be convenient, but they are ideal for routine maintenance. It’s advisable to go for professional testing when you reopen your pool after a long winter.

When and How Often Should You Test Pool Water?

One thing that makes pool water testing gives accurate results is the timing. And you know what, for you to ensure your pool water pH and alkalinity stay balanced, and the sanitizer at the optimal levels, it’d best to the pool water once a week.

You might also want to frequent the testing if your swimming pool gets a lot of use or it rains frequently, and you’re forced to add the pool chemicals.

Even if you’re a pro with pool water testing, it’s a good idea to take your pool water sample to a local pool store for testing once a month and during pool closing and opening.

Testing For Copper

If you have a cloudy pool situation or there are blackish or greenish stains on your liner, your pool water might be having a copper buildup.

It could be coming from the tap water you used during refilling. If that happened, as water evaporates, the copper is left behind. With time the copper ions increase and cause a buildup.

When you add more water to replace the water lost through evaporation, you’ll be adding more copper. When the evaporation cycle repeats, guess what? Copper levels continue to increase.

Another way copper could find its way to your pool might a cause of low pH. When the water is acidic, it can cause pool plumbing and filtration system to corrode. When the corrosion finds its way into your pool water, it feeds it with copper elements.

How do you test for copper?

Regular test strips do not test for heavy metals. It would be best if you had a unique test kit and the standard sets you use for testing chlorine, pH, alkalinity, and more. The best thing is, they are budget-friendly.

The manufacturer will offer an instruction manual on using the testing kit, but it’s precisely the same as using the regular test strips.

How often should you test for copper?

Unlike the standard water testing for alkalinity, pH and chlorine levels done weekly, copper testing should be done at least once a month.

Copper buildup doesn’t happen overnight, but you shouldn’t forget to test its levels regularly. Regular pool water testing for copper can help keep the metal at bay and escape its effects.

With low pH contributing to high levels, you will want to test it weekly and balance it regularly to avoid the copper buildup.

Testing For Iron

If your pool water is rust-colored or brownish, the might be an iron buildup. It’s pretty gross; I don’t you would want to jump in the water.

Similar to copper, the iron levels increase when the pool water pH is low. That’s why it’s always best to keep testing the water pH weekly.

Another source of iron contaminants is well water. If you use well water to fill your swimming pool water, it might have iron ions that you will be feeding to your pool water.

If the evaporation were to occur, the iron ions would be left behind and increase each time you refill your pool.

How do you test for iron?

You can use the same strips or kit you used for testing copper to test for iron presence in your pool water.

The only difference here is that once you take the water sample from your pool, you have to add a special solution designed to test iron levels.

Compare the watercolor with the color printed on the chart that comes with the package. Decode the iron levels in your pool and take the necessary steps.

If you want an accurate test of the minerals present in your well water before using it, you can test it too or take it to a certified water testing lab near you.

How often should you test for iron?

Like any other metal contaminant, you have to test your pool water for iron once a month. That will help you monitor the levels regularly to avoid brown or rusty water.

Testing for Calcium

You might be familiar with pool water hardness testing, which is determined by testing the calcium and magnesium levels in it. It’s a problem created by using hard water.

If there is calcium buildup in your bathroom faucets and showerheads, can you imagine what it’d pool filter and pump?

Too much calcium in your pool water can lead to cloud water, cause rough surfaces and reduce the efficiency of your pool heater.

Unlike copper and iron, calcium levels could be low too and cause other sets of problems for your pool, including pitted concrete pool surfaces, etched plaster, and dissolved concrete.

As time goes by without balancing it, the damages could end up needing expensive repairs. Balancing calcium levels is crucial in preventing these damages and save you money.

How do you test for calcium?

A calcium-balanced swimming pool should have anything between 200 and 500 ppm (parts per million).

You need a professional-grade pool water testing kit here. It will help test for the calcium levels and copper, iron, pH, chlorine, and other substances.

All you need is your pool water sample, add a chemical indicator and compare the watercolor to the color-coded chart provided with the package. Check and decode if the calcium levels are high or low.

How often should you test for calcium?

Test for calcium levels when your water is cloudy, when the pool line starts scaling, or when you begin to notice pitting in your pool concrete.

At this point, you’re late, but you can stop the damages by balancing the hardness. To prevent such damages and save yourself from the expensive pool repairs, test the calcium level once a month.

If you use hard or soft or refill your pool with well water high on calcium, you might want to increase the water testing frequency twice a month.

Testing for Salt

Are you using a saltwater system, or did you bought a home with a saltwater pool, or are you’re thinking of converting your chlorine pool to a saltwater pool?

If you fall under one of these options, you’ll have to add salt level testing to your regular pool maintenance schedule.

Similar to water hardness, salt levels can be an issue when too low or too high. When the levels are too much, they can throw the saltwater chlorinate into an overdrive.

And when the salt is too low, your pool won’t get enough chlorine, thus exposing it to issues that may affect the swimmers and your swimming pool.

Balanced salt levels mean more chlorine production, thus keeping your swimming pool protected against algae and bacteria.

How do you test for salt in your pool water?

If you want your saltwater running optimally and produce enough chlorine levels, you’ve to keep the salt level at approximately 3200 ppm.

You can use test strips since they are fast and easy to use when testing your pool water’s salt levels.

All you need is to collect the water sample in a test tube (provided with the kit), dunk a dry test strip inside the sample, and remove it. Please wait for 20 seconds and check it out for the results.

How often should you test for salt

Because of their simple and straightforward balancing, you can test your pool water salt once a month compared to other chemicals.

But if it were to rain and your pool gets a rainstorm, or you refill it with fresh water, or if you held a backyard pool party with lots of guests, you’ll want to test the water-salt levels again.

Digital Pool Water Testing

With everything going digital, pool testing hasn’t been left out. Today, mobile applications and digital devices make pool water testing so much easier for pool owners.

Pool Water Testing Apps

Every pool owner has a smartphone, even you. Right?

Well. If you search in your Apple App Store or Google Play Store, there is a whole set of pool chemical calculator apps. They are here to help you manage your pool maintenance from wherever you’re.

Some require manual testing and feeding the app’s data, and others need you to get unique test strips scan-able by the app.

All you need is to test the water chemistry and scan the results with the app. It will analyze and calculate everything for you and give you feedback and recommendation.

You can find a bunch of these apps here.

Digital Pool Water Testing Kits

Digital testing kits work similarly to smartwatches or smart home devices. They are like super-powered liquid test kits.

There are two types:

  • Some require you to do the handy work of testing the pool water, and they analyze the results with their digital readers.
  • And there those that are smart to do all the hard work for you. You install them into your pool, and they will test the water and render the data through an app on your mobile phone.

You can use digital test kits to check for about everything, including free chlorine, total chlorine, alkalinity, pH, bromine, calcium hardness, and everything there is to test. It’s a convenient technology bringing to the pool owners.


And that is everything there is to on how you test your pool water. And as you well know, owning a swimming pool comes with the responsibility of maintaining it, and pool water testing is part and parcel of the whole process. You’ve to take matters into your hands by testing and adjusting the pool chemicals every week.

Now that you know everything on pool water testing, you should check out our guide on pool water chemistry balancing to understand how you can keep your safe for your other swimmers and the pool itself.

About the author

Sharif Miah

Hi! I'm Sharif, the founder of Globo Pool® and I have been working in the pool & hot tub industry for the last few years. I love to share my experiences with people & hope you are enjoying my information and lessons!

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