Pool Water Testing | Keep the Water Pristine for Swimmers

Owning your own home swimming pool is as simple as installing it and filling it up with water, right? Not quite! If you want to truly get the most out of your pool and keep it in top condition for years to come, you’ll need to learn at least the basics of pool water testing.
Regardless of whether you have an in ground or above ground pool, one with salt water or fresh water, it is absolutely critical that you test and balance your pool water regularly.

In this guide, we will walk you through everything you need to know about how to test pool water. We’ll take a close look at how to take water samples, how to understand your water test readings, and how to properly use pool test strips, liquid test kits, and even the best digital pool water testers. 

Pool Water Testing Is Essential to Pool Health

We simply can’t stress enough how important it is to regularly test your pool water early and often. After all, a personal home swimming pool is a major investment, so why not take all of the necessary precautions to ensure the long term health of your pool?

Woman sitting on the pool edge

Unfortunately, unless you’re already an expert on pool water chemistry, you won’t know all of the important information on how to test and balance your water properly. That’s where we come in! We’re going to give you a crash course on how to test your water accurately, so you can adjust your chemicals as necessary to prevent algae growth and other unsafe and unsightly contaminants. Of course you need your pump primed (we covered that here) and working well so you can have good water circulation. Otherwise, forget about getting the best pool slides if your water is murky, dirty and unsanitized. Where's the fun in that?

If you follow this guide carefully, you can be sure that your pool will remain in peak condition for years to come, allowing you and your family hours of safe, clean summer fun—all without the guesswork and headaches that many pool owners face, especially if you have a pool automation system up and running.

How to Test Pool Water Accurately

The most important aspect of testing your pool water is do so in a way that will give you the most accurate readings. The first step in getting accurate readings, of course, is collecting a proper water sample from your pool. This is a crucial step to perform correctly, regardless of whether you are using pool test strips, an electronic pool tester, or a liquid test kit.
To get an adequate water sample that will give you the most accurate readings, you’ll need to follow these simple steps:

1. Get a clean container for the sample (depending on the type of testing equipment you are using, this may be provided).

2. Flip the container upside down, with the mouth of the container open toward the ground.

3. Find an area of your pool away from return jets or the pool skimmer—preferably in the dead center of your pool.

4. Submerge the container into the water until the water comes up to your elbow.

5. Flip the container right-side-up, which will let the water into the container, collecting the sample.

How to Use Test Strips

While not as accurate as a digital pool test kit, pool water test strips are very convenient, affordable, and simple to use. Also, they are clearly the most popular pool water testing option available, so we’ll go into their use in some detail.
Once you’ve collected a proper water sample from your pool, you’re ready to begin testing with your test strips. The process is fairly simple and straightforward.

1. Take one test strip and submerge the end of it into your collected water sample. This should be quick, not letting it soak in the water at all.

2. Remove the strip from the water sample and hold it in the air for 10-20 seconds. Be sure to hold it still—no need to wave it around or anything.

3. Now, hold the strip up to the guide provided with your test strips, comparing the colors.

4. Depending on your reading, you can now adjust the pool chemicals based on the results.

As noted before, though, test strips are not always the most accurate pool water testers. Unlike a digital pool test, test strips typically provide a range for its readings, rather than the digitized, exact results of the digital tester. Also, unless you get salt water pool test strips, the standard test strips to not test for salinity—a crucial factor for you if you have a salt water pool.

How to Use a Liquid Test Kit

While pool test strips are great for their convenience and ease of use, a liquid test kit is more likely to provide you with far more accurate readings.
The tradeoff with liquid test kits, though, is that they tend to be a bit more expensive, and the process is certainly more involved and prone to user error.
To help you avoid inaccurate readings from your liquid test kit, follow along with these directions, and you can be sure to get the best results.

1. Retrieve a sample of your pool’s water according to the sample collection instructions provided above.
Note: Liquid test kits almost always come with their own dedicated collection container. Use this for best results.

2. The test kit should have two separate tubes, now filled with your pool water—one marked for pH and one marked for chlorine.

3. Add the number of drops of phenol red to the pH tube, according to the instructions that came with your kit.

3. Add the number of drops of orthotolidine to the chlorine tube, according to the instructions that came with your kit.

4. Using a white piece of paper as a background, use the color scales provided on the container to compare with the colors of your pool water samples.

5. Adjust your chemical levels accordingly. We also covered a frequent question "what chemicals do I need for my pool".

Professional Water Testing

If you don’t think you will have the energy and time to test your pool’s water yourself, there are other options. You can always take a sample of your pool’s water (properly collected according to the aforementioned guidelines) to a reputable professional. 

Most pool and pool equipment retailers offer water testing services. It’s probably a good idea to call around for rates and availability, though many of these professional water testers offer walk-in water testing as well.

It may not be the most economical option for testing your pool water, but if you want to eliminate the possibility of user error and obtain the most accurate readings, this might be a good route for you to take.  

Professional testing may also be a better option for you if you have a salt water pool or live in an area with high mineral contents in your water. This is especially the case if you use well water to fill your pool. Using professional testing will avoid purchasing the otherwise necessary specialty testing kits. 

When to Test Your Pool Water

Determining how often to test your pool water can be a bit of a challenge. This is because the various chemicals you need to test for need to be tested at different rates. For the two most important readings, pH and chlorine levels, you should test weekly. However, most experts suggest testing for these readings two to three times per week.
We will discuss the frequency required to test some of the other chemicals in greater detail later in this guide. For now, just know that you should be testing the pH and chlorine levels of your pool’s water at least once a week.
Of course, beyond this regular testing, you should also test your pool water more often when it is being used more often. Also, if it has rained recently, and the pool wasn’t covered, it’s a good idea to test again before getting in the pool.
Important: You should always test your pool’s water both before and after adding any new chemicals. This is to ensure your safety and proper chemical balancing of your pool water.

Combatting Contaminants

Depending on the water quality you have available for filling your pool, you may need to test your water more or less often to combat unwanted and dangerous contaminants. For instance, the minerality of well water is much higher than water from other sources. This means you will likely see higher levels of metallic elements in your pool water.
If you are using well water for your pool, or live in an area with hard water (that is, water with higher calcium content), you will definitely want to test your pool’s water more frequently. These kinds of contaminants can leave stains on your pool surfaces and even cause more significant kinds of damage in the long run.

What Chemical Levels to Test for Regularly?

As mentioned above, you want to regularly test your pool water for pH and chlorine levels. These are the most important things to check to ensure your water is clean and safe for swimming.
Beyond those, however, you also want to regularly test for things like alkalinity, calcium, iron, copper, and phosphates. Now, you don’t need to test for these elements quite as often as pH and Chlorine, but intermittent testing for them will certainly improve water quality and extend the life of your pool.

High levels of copper, for instance, can leave your pool water looking murky or cloudy, and can even leave black or green stains on your pool walls. Yuck! You will, however, need a special kit to test for copper, in addition to what you are already using for pH and chlorine.

But what if your water has taken on a rusty brown hue? The likely culprit is high levels of iron. High iron levels, like high copper levels, are usually a result of low pH balance in your pool. Both are more likely if you are using well water to fill your pool. Luckily, you can use the same tests for iron that you use for copper.

Calcium, on the other hand, is one of the most damaging contaminants that might be present in your pool. High levels of hard water can cause scaling that builds up and can clog filters. It can even lead to etching in plaster and pitting in concrete surfaces that can be very expensive to repair. To test for calcium, you’ll need a professional level testing kit, or simply take a sample to a professional water tester.

How Often Do I Need to Test the Water?

When it comes to these other chemicals and contaminants, the frequency of testing is quite different than it is for things like chlorine and pH levels. For all of those that we’ve mentioned, monthly testing should be sufficient.
However, if you run into any of the indicators of high levels that we’ve discussed—cloudy water, rust-colored water, black or green stains, calcium scaling, etc.—then you’ll want to test for the respective contaminants right away.

Along with those elements, if you have a salt water pool, you need to test for salinity (salt levels) only once a month, using a salt water pool test kit. 

What Are the Recommended Levels?

yellow floater in the pool

Going through all this work of testing your pool water won’t do you much good unless you know the recommended levels for the various chemicals. In this section, we’ll go over the various target levels for each of the important readings from your water testing.

First, pH levels should be around 7.5 to 7.6. Keeping your pH balanced in this range will go a long way to promoting safe, clean water for all of your summer fun.

Next, you want to keep your chlorine levels between 1.0 and 3.0 parts per million (ppm). Of course, this reading will be much higher immediately following a chlorine shock to sanitize your pool more thoroughly. So be sure to wait at least 24 hours after a shock treatment before testing your chlorine levels again.
As for the other chemicals, refer to this list for recommended levels:

  • Calcium Hardness: 200 – 400
  • Total Alkalinity: 80 – 140 ppm
  • Cyanuric Acid: 25 – 50 ppm
  • Total Dissolved Solids (TDS): 500 – 5000 ppm

Which Pool Test Kit Is the Most Accurate?

While none of the available pool water testing options are completely fool proof, some are certainly more accurate than others. As mentioned above, pool water test strips are a great and affordable option, but they aren’t always the most accurate, as they usually only give you a range for your readings.

Liquid test kits are certainly more accurate than test strips; however, they too have a downside. Those more accurate results can be compromised by the greater potential for user error. To ensure the best and most accurate results, be sure to follow the provided instructions and our liquid test kit advice carefully.

Perhaps the most accurate option available for at-home use is to use a digital water tester. These tend to be more pricey, but they give you the most accurate results and often test for elements that the other testing options do not.

Of course, to get the most accurate readings for your pool water, you can always take a sample to a professional. Doing so will provide you with precise measurements of any factor you are interested in. 

Ana Stanar
 

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