What Is The Best Water Test Kit For DIY Swimming Pool Owners?

As a swimming pool maintenance technician for over 12 years, I get asked a lot about what test kit people should use when testing their backyard pools. It may surprise you to know that there are several options on the market, that will fit the bill. That being said, I will address 2 of the most common styles of test kits. Eyedropper style, and test-strip style.

The best all-around test kit for swimming pools in the eyedropper style category is the Taylor K-2006 kit. For DIY swimming pool owners who are more comfortable with test-strip style kits, the best out there is the Hach AquaCheck 7 test kit.

Keep in mind that many pool service professionals like myself are beginning to use digital testing methods that are accurate out to two or three decimal points, even using automated controllers. Since this article is directed at the DIY consumer who isn’t going to be spending the amount of money that digital testers will set you back.

In a future article, I will address some of the more advanced options that are available for testing swimming pool chemistry. When it comes to accuracy on a swimming pool test kit, the eyedropper-style kits are going to be about as accurate as they come for the DIY crowd.

There are also several specialty tests on the market for very specific parameters such as copper or iron content, salinity, phosphate levels, and so on… I’ll cover these specialty tests in another article.

Since Chlorine is usually what everyone thinks of when it comes to testing chemicals, that’s what I will cover first.

Which Is The Best Chlorine Test Kit?

The types of chemicals used in test kits, also known as a “reagent” (pronounced RE-AGENT), help identify not only which is most accurate, but which will suit your needs the best. In this first section, I am going to cover the dropper-style test kits, I’ll cover the test strip style in the next section.

The Best “Eyedropper” Test Kits

The eyedropper-style test kits use three main reagents in their test kits to test for chlorine.

1. OTO (orthi-Tolidine [orthotolidine])
2. DPD (N,N-diethyl-p-phenylenediamine)
3. FAS-DPD (Ferrous Ammonium Sulfate-DPD)

OTO (orthi-Tolidine [orthotolidine])

OTO Has been in use since the early 1900s. Today it is mostly only used in quick tests or ‘basic’ tests that are marketed to homeowners, rather than commercial pool service providers. An example is this Pool Master five-way test kit or Taylor K1000.

To perform an OTO test, five drops of the reagent are added to the water sample in the comparator (sample) tube and a color comparison is made to the color samples provided to determine the concentration of total available chlorine in the sample. This is what is known as a colorimetric test.

OTO is not recommended for commercial or professional use because of its drawbacks…

1. OTO measures total chlorine which isn’t an accurate representation of the available chlorine that is the actual sanitizing form of chlorine.
2. OTO has a very low pH which can skew a test result by activating HOCL or hypochlorous acid which is the killing form of chlorine, thus actually consuming part of the test sample before the result can be recorded. So accuracy is a problem.
3. OTO can also be affected by minerals and other compounds that are present in the water sample, reading such as total chlorine.

In short, OTO can’t give you an accurate representation of FAC (free available chlorine), TAC (total available chlorine), and CC (Combined chlorine) for you to be able to properly maintain your pool’s chlorine levels, which are necessary for accuracy.

DPD (N, N-diethyl-p-phenylenediamine)

DPD is widely used in the professional swimming pool community as a chlorine reagent. It first came into use in the mid-1900s. DPD allows you to test for FAC (free available chlorine) as well as TAC (total available chlorine). DPD is accurate between .5 and 10 parts PPM (parts per million) of chlorine. As a reagent, DPD is relatively pH neutral leaving the sample fairly unadulterated.

Similar to OTO, a DPD test is performed by adding five drops of two separate reagents to the sample in a sample tube and comparing the resulting color to the sample chart to determine the concentration of free available chlorine, A third reagent is then added to determine total available chlorine. The free available chlorine number is subtracted from the total available chlorine number resulting in recorded combined chlorine. 

An example of a test kit that includes DPD is this complete kit from Taylor K-2005 Or this basic kit from Taylor K -1001.  

While DPD is superior to OTO in many ways, there are still drawbacks to consider…

1. liquid DPD reagent has a relatively short shelf life of six months up to a year. This is why it’s a good option for professionals who test numerous pools in a short period of time.
2. At high chlorine sample levels the coloring dye can actually be bleached by the chlorine sample, which will give a false low reading. This is counteracted by adding more DPD to the sample or performing a dilution test
3. If high calcium levels are present in the sample they can adversely affect the DPD test, turning the sample cloudy
4. High chloramines (an ammonia/chlorine byproduct) in the sample can present as free chlorine if the sample isn’t read fast enough.
5. Higher temperatures can also cause Skewed readings

Even with the drawbacks, the majority of health authorities in the United States use DPD test kits as a means for measuring chlorine In Pool water. DPD continues to be a reliable test for professionals and homeowners for consistent results.

FAS-DPD (Ferrous Ammonium Sulfate-DPD)

Whereas OTO and DPD are color comparison tests a.k.a colorimetric that turn color and increase in intensity depending on the test results and require you to be able to compare test results with a standard color chart. The FAS-DPD test is what’s known as a chlorine drop count test, or titration test. In this test, you get the water sample, add a reagent that turns color right away, and then add a second reagent by counting drop by drop until the color turns to clear. The number of drops is then multiplied by a specified factor to determine the concentration of combined chlorine. Here’s an example of a test kit that uses FAS-DPD, Taylor K-2006 & Taylor K-2006 Salt

Of the three, FAS-DPD is my favorite because it takes the guesswork out of the color comparison. Especially when high-quality light is unavailable. And I can imagine if someone suffered from color blindness trying to read a color comparison chart would be quite difficult. Of my time using the FAS DPD method, I have only been able to find two real drawbacks.

1. the DPD powder cannot get wet or it will clump up
2. The test takes slightly longer.

Of the three dropper-style tests, I’m sure it’s obvious which I prefer, but you have to go with what suits your needs. Let’s take a look at the different strip-style kits.

Test-Strip Swimming Pool Test Kits

Like dropper tests, not all pool test strips are created equally. Various manufacturing methods can affect both the speed and accuracy of the testers. Some strip testers are on the more basic side, testing for 3 or 4 parameters. While others test for 6 or 7.

Test strip manufacturers use two primary reagents to detect and record chlorine.

1. Syringaldazine
2. TMB (tetramethylbenzidine)

Syringaldazine

Syringaldazine is a great reagent to use. It went into use in the 1980s. It reacts with FAC (free available chlorine). The great thing about syringaldazine is that it is accurate from 0.1 ppm to 10.0 ppm. Unlike many other reagents there, it won’t be affected by many of the other compounds that are found in pool water.

Syringaldazine is of the more common test strip reagents found on the market. Here are a couple of examples. Hach AquaChek 7 and Poolmaster Smart Test.

Some test strip manufacturers produce very high-quality strips for both professional and end-user consumers. Test strips can be a much more economical way to monitor your swimming pool’s chemistry balance. It can be argued that some test strips rival the accuracy of many dropper-style test kids on the market. I know in a pinch wow on my pool service route I have on occasion used test strips and been fairly impressed with their accuracy.

Best Test Kit For Swimming Pool pH, alkalinity, calcium & cyanuric acid?

You probably caught on by the 2nd test kit that I was only talking about chlorine testing. That’s because chlorine is the most complex of the tests and it’s where there seems to be the most discrepancy.

Testing pH with Phenol Red

When it comes to pH all of the tests pretty much use what’s called phenol red reagent to test for pH. Whether it’s a test strip or a dropper-style test the pH test is going to be colorimetric.

Because phenol red gets darker red to magenta as the pH increases it is limited by how high and how low it can take accurate readings. In general phenol red will read a low of 6.8 and a high of 8.2. This is where a professional dropper-style test kit like Taylor K-2006 really comes in handy because the user can run an acid/basic demand test even on out-of-range readings to determine the needs of the pool. This is not an option on basic test kits and test strip-style kits.

Where chlorine is in the higher ranges, it will tend to bleach out the pH test giving a lower reading than what is accurate. To combat this the higher-end dropper tests include a chlorine neutralizer solution that can be added before the pH test. Basic kits and test strips don’t have that option.

At the beginning of my career, I had a pool with higher chlorine that kept bleaching my pH test and I didn’t know it until a co-worker set me straight after about 6 months of servicing the pool.

Calcium, Total Alkalinity, and Cyanuric Acid

At the risk of becoming redundant, testing TA (total alkalinity) as well as CH (calcium hardness) when using a dropper style kit are both titration tests like the FAS-DPD test. Rather than colorimetric tests where you need to compare colors, a titration test requires you to count how many drops it takes to turn a sample into a particular color.

For example, in the TA test in a Taylor K2005 or 2006 test kit after adding a pH adjuster you then add a reagent that dyes the sample green, then another reagent is added drop by drop until the sample turns red. The number of drops is then multiplied by 10 to give you the recorded result.

In the case of CH and TA, the dropper kit is more accurate than the test strips. Even still, if your preference is test strips, I would recommend getting the strips that include CH and TA in the test results because it will give a close approximation of these two parameters.

Before moving on to the all-important CYA test… Some things to be aware of on the total alkalinity and calcium hardness tests. It’s a known issue and one that I have run into numerous times in my career, high chlorine in the sample water will absolutely bleach the TA and CH samples. The only remedy to this issue when using a test kit is to add 2-3 drops of chlorine neutralizer to the sample first. A chlorine neutralizer is usually included with any high-quality test kit.

Unfortunately, there is no remedy to this issue when using test strips. One possibility is to take the sample in an isolation cup instead of directly from the pool or spa and neutralize that sample before dipping the strip, but then you don’t get a chlorine reading.

Testing for Cyanuric Acid (CYA)

The use of chlorine stabilizer, aka water conditioner, aka cyanuric acid within the pool industry has become increasingly popular in recent years. This naturally means we need to be able to test for it.

To better understand what CYA is and why it’s important to understand head over to this article on “How To Add CYA To Your Pool Water” after you’re done here. Here’s one very important tidbit about CYA, it does not leave your pool through evaporation or use like other chemicals so it’s very important to monitor its levels. Especially if you use chlorine tablets (pucks), or granules.

When using a dropper kit the CYA test is a turbidity test. Basically, you will take a specified sample amount of the pool water, then mix in the reagent until it is fully incorporated into the sample, then based on the amount of turbidity (cloudiness), the quantity of CYA can be determined. In the case of the Taylor test kits, there is a dot at the bottom of the test vial and as the cloudy sample water is added you’ll watch from the top of the vial until you can’t see the dot any longer, and this determines the amount of CYA that is present in the pool.

Again, in the case of test strips that include a CYA test, they are not completely accurate, but they give you enough information to know if further investigation is needed.

Are Test-Strips or Test Kits Better For DIY Swimming Pool Owners?

If you have read up to this point it should be obvious that I prefer the Taylor K2006 test kit, in fact, I like the K2006-Salt version because it’s the most versatile and complete way to test in the field for a swimming pool professional. But what about you, the DIY swimming pool owner?

Are you the type that likes to know all the specifics? Will you do all the research that is needed to know what the tests mean, and all the calculations to know how to make adjustments? Or, are you the type that wants a quick visual confirmation that the pool is safe to swim in today, and when you get to it you will go to the pool shop and buy what they recommend?

The Pool Master five-way test kit, OTO gets the job done by allowing the DIY homeowner to test for chlorine, bromine, pH, acid, and total alkalinity. It includes an easy-to-read testing block. The OTO reagent has a long enough shelf-life so you don’t have to worry too much about an expiration date. if budget is a concern, these tend to be on the more affordable side of the spectrum and are pretty much available at most hardware and some larger grocery stores like Walmart.

The Poolmaster Smart Test will give you a quick sanity check to make sure the kids are safe and not much more. Since they are test strips, they have a superior shelf-life. It’s a 3-way test so it gives you the parameters you need for life safety, without extra diagnostic tests. A bottle of 50 strips is pretty affordable.

If you like more information, but still like the quick visual approach, the Hach AquaChek 7 is the way to go. For not much more out of pocket, you get 4 more tests per strip and you get 100 tests per bottle. Many pool service companies actually use these as an alternative to using dropper kits at every stop because it speeds up their day and is accurate “enough”. If I was going the test strip route, I would go with this pick.

The DPD dropper-style test kits like the Taylor K-2005 are great. The main drawbacks that I see for a homeowner are (1) the initial cost is pretty high by comparison to the test strips and (2) the DPD reagent has a shelf life of only 6 to 12 months. Most homeowners that I speak to end up testing their pool on average twice a month during the swim season and maybe once during the offseason. This isn’t necessarily a deal-breaker if you don’t mind replacing the reagents every other year. This is an option because the rest of the test kit will do just fine if stored properly.

THE WINNER!

Finally, the FAS DPD kit Taylor K-2006 is far superior and more advanced than the others. As far as affordability goes, it is the most expensive if you get the complete kit. You might be comfortable getting the basic Taylor K -1001 kit and then picking up another cheaper kit to test the rest of the chemistry. personally, I would look at it as an investment in your family’s safety and pay the extra money for the complete kit.

How To Use Swimming Pool Tests

Believe it or not, there is a right and a wrong way to use these tests. It’s important to follow closely the instructions provided with your test kit. Here are a couple of highlights that you’ll want to watch.

• always test before using the pool
• take your sample from as far down as you can reach. Most test mfr instructions say 18 inches down. This is so the sample is plenty mixed with the rest of the pool.
• use the test vial caps when mixing reagents. Reagents are toxic chemicals that should be treated with respect.
• When using droppers, hold the dropper perfectly vertically to get a complete drop.
• Don’t wait to record the test results as the colors will fade within a few seconds in some cases
• when performing a colorimetric test make sure you are in even light with the sun to your back if possible, or out of the sun even better.
• store test kits and strips in a cool dark place. A metal storage shed is not the best place.

Hopefully, this article has been of help to you. Feel free to share it around. Join my mailing list to get notified of new information, and head over to the PoolProAnswers YouTube channel.

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