Beginner’s Guide to Pool Water Testing

testing-pool-water - the wrong wayWe have all heard of “testing the waters” but when comes to swimming pool maintenance, water testing is the best route to an easy to maintain pool.

You have to do more than touch the water to test anything more than the temperature. Test kits, strips and readers are used to check pool water balance levels.

A swimming pool is just a hole in the ground without water, and swimming is no fun if not experienced in clean, clear and healthy water.

Since swimming pools are generally used by multiple people at any given time, it is imperative that pool water is tested and treated regularly to prevent the spread of infectious illness and enhance the pool experience.

In order for us to have a sparkling clean and well-balanced pool, we have to ensure that the levels of pool chemicals stay within the ideal range of:aquachek-7-way-test-strip-color-chart

  • pH: 7.2 – 7.6
  • Alkalinity: 80 – 120 ppm
  • Calcium Hardness: 180 – 220 ppm
  • Chlorine: 1-3 ppm
  • Bromine: 3-5 ppm
  • Cyanuric Acid: 30 – 50 ppm

Testing your pool water and maintaining perfect chemical harmony is not rocket science but it definitely involves regularity and consistency on your part. It is recommended to test your pool water weekly and add chemicals if you see an increase/decrease in ideal chemical levels. There are several types of testing supplies available on the market varying in price and accuracy.

Since I work for a company that sells pool supplies, it was fairly easy for me to get customer input via our amazing review program, and I was able to narrow down the bestselling water testing supplies to make it easier for you to make the selection to your liking.

Pool Test Strips:

pool-test-stripsThe most inexpensive and widely used method of water testing – test strips – is fast, easy, and fairly accurate. Water testing strips like the AquaChek Test Strips can be used to test for individual chemicals or you can buy something like AquaChek Select 7 Way Test Strips or YellowYellow 4 Way chlorine test strips to make multiple tests at the same time.

The most amazing feature of test strips other than their low price is that they are very simple to use; just dip them in water, swirl and read the results within seconds. Usually the test strips are color coded and come with an easy-to-read chart that lets you easily determine which chemicals you need to add to your pool.

Liquid Test Kits:

taylor-troubleshooter-test-kit-Liquid test kits are an excellent way to determine chemical levels in your pool and maintain crystal clear water at all times. Obviously higher in price as compared to testing strips, the liquid kits offer a more reliable and complete testing solution. Liquid testing kits like the LaMotte ColorQ Pro 7 Water Chemistry Liquid Test Kit make use of reagents that are added to sample water and results are read on a user-friendly comparator.

Liquid testing kits like the 4-Way Test Kit Liquid Solution are economical and easy to use, and some like the Taylor Basic Residential DPD Test Kit take maintenance a step further and include a dosage chart for translating test results into treatment.

Digital Pool Testers:

digital-pool-testerWhat is the first thing that comes to mind when you hear the word digital – accurate and fast, right? Well when it comes to digital water testers, accuracy and promptness is what these amazing testers offer. Extremely easy to use, the digital water testers often feature LCD display, water-resistant housing, memory function, and no color matching, so reading results is a snap.

Digital pool testers have electrodes that measure chemical levels in the water with results that have more accuracy and dependability. Of course more on the expensive side, Digital water testers are definitely my favorite for a reliable, complete and fast water testing solution.

As a pool owner, you know that pool maintenance is not easy and does not come at a flip of a button. Regular pool testing is an important foundation to prevent other pool problems. These water testing solutions mentioned above are perfect to keep water balance easy and make your overall pool maintenance a little lighter.

balanced-happy-pool-waterTest Strips, Test Kits or Digital? The type of pool test you use depends on the level of accuracy you want in your pool tests. Test strips are the least accurate, a liquid test kit has better results and a digital reader is most exact and also rules out [most] human error!

Until next time, adiós!

Ayesha Aslam
InTheSwim Staff Blogger



Beginner’s Guide to Pool Water Testing — 20 Comments

  1. Hi I to this hot tub stuff but I sure like it. I have not mastered on how get the water balanced correctly. So to start I am using aqua check test strips. First question is does it matter if more than one chemical added at a time? Additionally the biggest issue right now is for me to understand that if the ph is off, like really off, (it is often purple) does that mean it needs to come up or down? I have both a ph increaser chemical and a ph decreaser chemical. Then assuming I eventually get an accurate ph reading do I then look to acquire accurate readings of the other chemicals? Please help… thanks. DD

    • Hi deb, When pH is really purple that means that it’s too high, or basic, when it’s really yellow, that means it’s too low, or acidic. Anything below 7.0 neutral is more acidic on the pH scale and anything above 7.0 is turning basic. The best range for pools and spas is 7.2-7.4. Too high and scaling and cloudy water can occur, and sanitizers are very slow to react. Too low and staining and corrosion can occur from acidic water. Use the pH decreaser if pH is above 7.8, and use pH increaser if it goes below 7.2. If it seems to bounce around a lot and your pH is ‘erratic’, check the total alkalinity, it should be 60-80 ppm in high calcium hardness water (over 400 ppm) or 100-120 ppm for soft calcium hardness water 150-200 ppm. However, for a Purple pH test result, it could be that the sanitizer level is so high that it is interfering with the test, if you suspect it is, you can dilute the test solution by half, but only with a test kit, not test strips.

  2. I bought a 15′ x 48″ round Intex pool (blow up top ring) a couple of weeks ago. I am having a hard time with the testing. I filled the pool with well water running through an in-line hose filter. The filter with the pool is 1000 gph. When the pool was full, I put .5 lb of shock in it which was the recommended amount. A few days ago, I put in another .5 lb of shock. I am using a floater with 3″ tablets. My pH, alkalinity, and chlorine levels are very low. I tried adding baking soda and that helps a little. I tried putting more than 1 chlorine tablet in the floater. I have tried 2 different testers (Poolmaster strips and Taylor test kit). The pool water is clear and no slime on the pool walls or floor. We swim almost every day. Besides the readings being very low, everything else is good. What am I doing wrong? (sorry for the long post)

    • Hi Renee, thanks for all the info, prefer long posts… likely you have very low stabilizer level (Cyanuric Acid) in the pool, and if testing during sunlight hours, it may be very low (chlorine). Adding 2 lbs of stabilizer would raise the cyanuric acid level to 20 ppm, per 10,000 gallons. Secondly, I would double shock the pool with an entire bag of shock, in the evening. If the chlorine level rises and remains for at least 8 hours, still there in the a.m. – good. If it’s zero again, repeat the dose, but double it to 2 lbs of shock – trying to reach a breakpoint threshold where whatever is consuming the chlorine is eliminated. Then raise the pH level using pH increaser, baking soda will also work, but will raise alkalinity more than pH. As long as you can keep it 7.2-7.8 (pH), it’s good. Below 7.0 and the water becomes slightly acidic and below 6.5, it will begin to eat your pool 🙂

  3. Have a sand filter thats stopped working that is now fixed my pool was almost clean just cloudy but itnis. Ow green the walls are not slimy i added 2 bags of shock and let the pump runnfor 24 hours while backwashing here and there. No color change at all what do i do. Also whem do i use ph kit and do i had increaser before or after addimg different shock treatment

    • Hi Sam, test your pH every few days, or at least 1x per week. Chlorine works most effectively in the 7.2-7.4 pH range. When it’s near 8.0, chlorine is very sluggish, and over half of it is impotent. Resist the urge to backwash, until filter pressure has risen at least 5 psi – sand filters work better when they are a little dirty. Using a clarifier could help clear the water. When shocking for algae, have a low pH, and keep adding shock until the water turns a blue/grey color, depending on the severity, it can take 2,3,4 or more lbs of shock, per 10000 gallons of pool water. When it turns blue-ish, with no hint of green, add one more pound, for good measure, brush the pool and run the filter all night.

  4. I use a test strip to test the water in my above ground 15×30 pool. The chlorine level shows almost white (very low) although the total chlorine seems to be at a good level. I did two tests just to make sure. How can that be? What should I do to adjust it? All other readings look good. Hardness is a little low. I shocked the pool last week and have also added powdered chlorine a few days after that.

    • Hi Bob, total chlorine is made up of Free chlorine + combined chlorine. If your total reads high, but your free reads low, the difference between the two is chlorine that has combined with something, to be the dreaded ‘chloramine’ – no longer an active sanitizer, and responsible for strong chlorine smell and red eyes. The solution is to add enough shock chlorine all at once to break apart the molecular bonds holding your chlorine hostage. For a 15×30 pool, around 10K gallons, I’d go with 3 lbs off shock, predissolved in a bucket of water, and poured around the edge.

      • The shock chlorine link you have in your comment above says NOT to dissolve in water. Is there a reason you say to dissolve it first?

        • Hi Bob, I believe that to be an error, and I have alerted the web team to correct. For any vinyl pool, pouring shock directly in the pool can cause the liner to bleach or fade, over time. Wont’ normally happen if you do it once (although it may). So, I advise to fill a clean 5-gal bucket with pool water, then pour the shock in, and use a stick or rod to stir to dissolve. Then pour in the water, but when the bucket is almost empty fill again with water, to dissolve remaining granules. Plaster or concrete pools and maybe fiberglass dont’ need to pre-dissolve, but for painted pools and vinyl pools – it’s a good idea to do so…

  5. Hello. I have a 5300 gl round pool I just started and have never had a pool before. I shock the pool yesterday afterwards 6pm and in the morning test the water with a strip. I am using a floder with a 3′ chlorine tablet and have the setting on hight the tablet is for a 10000 gl
    Chlorine is 10
    Chlorine free is 10
    Total hardness is 500
    Ph is 6.8
    Total alkaline is 120
    Stabilizer is zero
    What should I do Please help thank you for your time

    • Hi Tyson, sounds like you are grasping it, and you’re almost there. To protect chlorine from the sun, add a small amount of cyanuric acid, just 16oz, or 1 lb, to build up a residual. then secondly I notice hat your pH is low and alkalinity high. Add pH increaser, about 2 lbs of soda ash, to raise pH level to 7.4 range. The chlorine is very high from the shocking, but should come down today/tomorrow, then your tablets will maintain the level, in the 2-3 ppm range. Hardness is quite high, but not much you can do about that, should not be a problem. Sounds like you’ve almost mastered the chemistry, the other thing to pay close attention to is the amount of daily filtering and circulation. Your filter may be a bit on the small side, and you may need 18 hrs per day of filtering, or more, to compensate. Use a timer for best results, so you don’t forget to turn it back on!

  6. Hi

    I tested my pool for alkalinity this morning using an electronic tester one side read the alkalinity ar 120ppm the other side read 170ppm is this possible. Ph is looking w at 6.7. I’m finding it difficult to regulate the ph due to the alkalinity.

    • High alkalinity and low pH is one of the most troublesome conditions to deal with. You need to lower the pH to also lower the Alkalinity (using pH decreaser or muriatic acid), and then your pH goes too low, and you need to raise it back up, but the high Alkalinity fights the change in pH, by buffering the pH too much. It may be cheaper and easier to drain half the pool, refill with source water of a lower alkalinity and higher ph (use your test kit to test your hose water). Otherwise, buy the large bucket of pH decreaser, and the large bucket of pH increaser, and treat the pool each day over the course of a week, and you should be able to realign the two.

  7. Good morning! I tested the pool and seems like everything was in balance but water is greenish color. You can see the bottom but water is green. Its not slimy but I bought the yellow mustard chemical and put in the pool along with 2 lbs of chlorine. This morning still the same vacummed it and according to strip there was no chlorine so I added 2 lbs again of chlorine. Not sure what to do next.

    • Hi Jackie, keep adding chlorine shock until you see the water turn a blue/grey color. For dark green pools that can be over 10 lbs of pool shock. I would avoid yellow out (sodium bromide) and just use lots and lots of shock, with the pH on the low side (7.1-7.3). When the chlorine level drops to zero the morning after a shock treatment, the chlorine demand was higher than the treatment dosage. Double it and try again!

    • Hi – on most pH tests, yellow colors indicate low pH, and thus requires pH+ to raise the pH. ‘Bright’ yellow may also mean that the reagents are expired, or that the chlorine level is very, very high.

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