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Pool Water Testing – Your Complete Guide

A swimming pool is an ideal oasis on a steaming hot day. Keeping your water clean and clear might seem mysterious or labor-intensive. But with a bit of know-how, you can complete all of your pool water testing chores simply and easily and for very little money.

Doing so will save you money, keep your pool looking its best, and minimize the risk of it turning green before your big party or on the hottest day of the year.

All it requires is a quality testing kit and a bit of knowledge. Keep reading, and you’ll learn everything you need in our easy-to-follow guide to pool water testing.

Why Test Pool Water?

Pool water testing is essential for keeping your sanitizing chemicals and water chemistry in the sweet spot for swimming. Consider that without chlorine or another sanitizer, the water can develop algae and become green quickly. But, if you use too much chlorine, the water will be harsh and unpleasant.

That’s just one reason why testing your pool water is essential. But there’s also another benefit to testing the water yourself.

You can save a lot of money by skipping out on testing your water at the local pool store, where they’ll try to sell you a bunch of stuff you don’t need. Hiring a pool service professional to handle pool water testing is even more expensive.

Testing is important. But it’s also pretty easy!

What Does Pool Water Testing Show?

Each pool water testing kit is a little different, but they’re all looking for the same few things.


Chlorine is the most common sanitizing agent used to prevent organics from living in your pool. There are three types of chlorine measurements, but free chlorine is the most important. The ideal level should be between 1.0 and 3.0 parts per million (PPM).

Calcium Hardness

Calcium hardness measures the total calcium dissolved in your pool’s water. Too much calcium can make the pool’s water unpleasant, just like when you have “hard water” in your home. The ideal calcium hardness is 200-275 PPM for plaster and concrete pools and between 175 and 225 PPM for vinyl or fiberglass pools.

Total Alkalinity

Total alkalinity closely corresponds with overall pH. But it can help you fine-tune the water a bit farther. Keep your readings between 80 and 120 PPM.


When your water is too base or acidic, it becomes unpleasant to swim in and can create a burning sensation if you open your eyes underwater. Plus, when the pH is too low (acidic), the water becomes more corrosive to your pool and its hardware and plumbing. So, keep your pH between 7.2 and 7.8 PPM, and aim for an ideal level of 7.4.

Cyanuric Acid

Cyanuric acid is a chlorine stabilizer. It helps prevent the chlorine from burning off in the sun, helping it last longer and saving you money.

Other Tests

Those are the big four in testing, and almost every test kit can measure them. Some test kits also measure:

  1. Bromine – an alternative to chlorine.
  2. Total dissolved solids – a measurement of substances dissolved in the water.
  3. Metals – If you’re seeing staining on your pool’s fixtures, you might have too much
    copper, iron, or manganese in the water. Ideally, you should have 0 PPM. You can use chelating agents to bond with and help remove metal if needed.
  4. Salt – Some swimming pools use an electronic cell to create chlorine from salt molecules. The ideal salt level for a salt pool is about 3400 PPM.

Stay Safe With Pool Chemical Testing

Before you test the water, consider how you handle your pool chemicals. Chlorine tablets and granules are caustic and can stain your clothes, and they’re harmful to your skin, eyes, and lungs when mishandled.

Always use the material safety data sheets for the chemicals to understand how to handle them safely. You may need to use gloves, an apron, and eye protection, especially if you are very sensitive.

How to Test Pool Water

Pool water testing starts with getting a high-quality testing kit. Testing kits come in three main styles.

  • Test strips come in a small bottle. You dip them in the water, and little squares change color to indicate your readings. They’re convenient and inexpensive but not as precise as a liquid testing kit.
  • Digital pool testers are electronic and detect multiple parameters. But they were expensive!
  • Liquid reagent kits are the most accurate. But, using one involves mixing samples of water with various chemicals. Their reaction generates a color change that you compare to a chart.

Test strips are the most straightforward method, and unless you are dealing with something more complicated, they’re probably the best.

1. Prepare To Test

Get your kit ready and make sure you understand the instructions. It’s a good idea to ensure that the pool’s filter is running, so the water is well-circulated during your test. Your hands should be clean and dry so you don’t contaminate your sample.

2. Perform Your Test

Perform your test according to the instructions on your test kit. If you’re using a reagent kit, you may have to do more than one sampling, so make sure to rinse everything out between tests. It’s a good idea to avoid touching anything sensitive until you’ve washed your hands.

3. Read Your Results

Take a look at your results. Make your adjustments in very small increments. It’s very easy to add a little more of most chemicals, and sometimes, adding one affects another’s reading. It’s usually very difficult to remove them from the water if you add too much. And, it’s a waste of money.

Consider adding a smaller dose than you think you need and letting the water circulate for a day or at least a few hours. Then, retest and add more if necessary.

Pool Water Testing Tips

To make things easy, keep these tips in mind.

Be Prepared

Keep your chemicals handy. Buy a supply for each season so you can cut down on trips to the store. You can also save money by shopping for bundle discounts and act quickly when your tests reveal an issue.

  • Adding chlorine – Sold in slow-dissolving tablets and sticks or fast-acting granules. Some people use bleach instead.
  • Lowering the pH – You can buy chemicals labeled ‘pH down’ or use muriatic acid to lower the pH
  • Raising the pH – You can find chemicals labeled ‘pH Up,’ but they’re mostly just soda ash. You can save money by using generic soda ash or Borax. If you need to raise the pH but don’t want to increase total alkalinity, aerate the water.
  • Raising calcium hardness – Use calcium chloride or calcium chloride dihydrate. It’s available in bulk at some big box stores, or you can find it under various names like ‘Hardness Booster’ at your local pool store.
  • Cyanuric acid Cyanuric acid is a specialty chemical for swimming pools, often sold in containers that say ‘chlorine stabilizer’ or similar. The best way to add this granular product is to fill a sock with your desired amount and let it sit in the skimmer. This is to prevent it from clumping up and blocking water flow.
  • Salt – If you have a salt pool, buy some water softener salt or pool salt. The only difference is the size of the granules or crystals. You can dump it directly into the pool, but it’s a good idea to turn the chlorine generator off when doing so. Leave it off for 24 hours and use a brush or your feet, to make sure that there are no piles of salt on the floor of the pool.

Test Regularly

Once you start pool water testing, you’ll get to know your pool and how to keep it looking its best. This will make it easy to plan for events that can affect the water’s balance, chemistry, and cleanliness.

Consider testing chlorine levels a few times a week, and make sure you’re testing pH at the same time. After you develop a rhythm of adding chemicals according to a loose schedule, you’ll be able to test less often.

Remember that certain times of the pool season require more testing than usual. Plan to test anytime:

  • You open the pool for the season.
  • There is a big storm that adds rainwater.
  • After a period of heavy use.
  • Anytime little kids, pets, or other sources of organic contamination are in the water.
  • When you close the pool for the season.

Pool Water Testing With St. Cyr Pool & Spa

Now you know everything about pool water testing. Get yourself a test kit today, and you can start managing your pool water’s quality and cleanliness effectively and easily. Keep your hot tub chemicals on hand, so when you need them, they’re ready and waiting.

And maybe most important, know when to ask for help. St. Cyr Pool & Spa’s team of experienced professionals is waiting to assist you.

If your water is turning green or you’re having trouble managing your hot tub’s water and chemicals, contact us today!

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