The Ultimate Guide to Testing Your Pool Water

We’ve gone over pool chemicals and pool water testing a number of times on our blog but we’ve realized that we’ve never really done an ultra-comprehensive guide on pool water testing. That’s going to change today with Mr Pool Man’s Ultimate pool water testing guide. We’ll go over every single value that you can test for in your pool, what they mean, and how to correct levels that are out of bounds.

Three Main Pool Testing Methods

For testing pools, there are three main methods that a home pool owner can utilize to properly test their pool water.

  • Pool Test Strips – Easy, just dip into pool water and wait a few seconds for the results. Limited to whatever reagents are applied on the strip and may be a little bit inaccurate.
  • Liquid / Reagent Pool Testing Kits – A little bit more involved but is very accurate. Reagents can be purchased as a kit or as individual reagents for different tests. Ultimate customizability / you can test for one or all values that you think need testing for. Needs a steady hand to drop in reagents accurately. These can be manual test kits where you have to interpret the results via color coding, or digital testing kits where a device reads the results for you and gives you a numeric reading instead of a color reading.
  • Professional Pool Testing – Easiest pool testing method, most accurate, but can be costly. Simply get a water sample and bring it over to your pool shop for testing. Recommended if things have spiraled out of control, but with proper pool maintenance, it shouldn’t reach this point.

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When should you do pool water testing

As a rule of thumb, we encourage every pool owner to test their pool water at least once a week to ensure that there are no wild swings in your pool chemistry. Remember that with pool chemicals, slow and steady wins the race. We want to be able to spot pool chemical fluctuations as early as possible to avoid losing control and keep chemical adjustments as minimal as possible. Aside from weekly testing, here are some situations where pool water testing is called for.

  • After a pool party – Having extra load on your pool will definitely throw your pool balance off. So after you have guests over or there’s extra-heavy pool usage, test your pool and balance as needed.
  • After a rainstorm – Rain and other debris will undoubtedly affect your pool chemical levels. Vacuum your pool, remove all of the debris, and test your pool to bring your pool chemical levels back up to where they’re supposed to be.
  • After adding water – If your pool water levels have gone down due to evaporation or for any other reason and you need to bring your water levels up, check your pool chemical levels after the water has been circulated and adjust as needed. New water will dilute your chemical levels and you’ll need to add more chemicals as a result.
  • Before and After algae treatment – If you’re battling algae, you will need to check your pool’s pH levels to ensure that your pool shock is as effective as possible. After shocking your pool, you also have to test and rebalance your pool as the pool shock may have altered your chemical levels as well.
  • Before closing your pool for the winter – We’ve already included this in our Pool Winterizing guide, but we just thought that it was prudent to remind you that testing is the required first step in winterizing your pool.
  • Opening your pool for the summer season – After a long period of disuse, your pool water may need adjustment even if it looks fine. Test and readjust your pool water chemistry as you open your pool for the season.

Collecting Water for Pool Testing

One of the first things we should remember (and is often unmentioned in many guides) is that to test the real state of your pool water. There are certain areas of the pool where you should get your sample from and there’s a method of getting the pool water sample to get a good representation of your pool’s chemical levels.

Where to get pool water samples

The two places to avoid when getting a pool water sample for testing are the areas around your return jets and skimmers. Water around your return jets may give you a reading that’s not representative of your pool water’s overall condition as it has just been filtered and may have passed through a chlorinator on the way back to the pool, which will give you a much more “cleaner” result.

The opposite is true for water around your skimmers, this is where the pool water “lines up” before getting sucked into your filtration system, getting water from this part of the pool may show higher concentrations of particles and may trick you into thinking that your pool water is “dirtier” than it actually is.

The best location to get pool water samples from is somewhere in between your return jets or skimmers, as this is the true “average” representation of your pool water’s chemical levels.

How to get water samples

Once you’ve determined the location to get your sample from, take a vial or small vessel, dip it into the water opening side first to trap the air inside, bring it to about a foot in depth and turn it over to let the air escape. This way you’ll be getting your pool water sample away from the surface and you’ll be getting a more accurate reading.  

Testing your pool water

To test your pool water using the samples that you have collected, follow the easy steps below.

  • Pool Test Strip – Simply dip the test strip into the water you have collected, hold the strip with the test dots facing up or place on a dry and level surface and wait until the recommended time indicated on the container. Do not shake it as it may cause the reagents to spill over to the others. Once the time as elapsed, compare the colors on the strips against the printed instructions on the container.
  • Liquid / Reagent Pool Testing Kits – Drop the required amounts of reagents into your testing vials and check the results against the included levels. For more information on how to test your pools using reagent test kits, click on the button below.

What to Test your Pool Water for

Here’s the fun part of the blog post, what figures to check for and what to do incase your levels are out of their required values.

Testing for Pool pH

Pool pH Optimal levels: 7.4-7.6

When your pool pH is above 7.6 this means that your pool is too alkaline. This means that your pool water is in a scaling or basic condition. Having a high pH level will reduce the effectivity of your pool sanitisers (chlorine) and can lead to pool scaling and calcium formation. To reduce your pH levels, add some acid or some pH down to bring the pH levels back down to optimal levels.

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When your pool pH is below 7.4 this means that your pool is too acidic. This can lead to increased corrosion of your pool surfaces as well as irritation to the eyes and skin of the swimmers. To raise your pH levels, you need to use baking soda (you might have to use a LOT of it though) or a specialized alkalinity up powder designed especially for the job like the Zodiac Alkalinity Up powder.

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Testing for Pool Total Alkalinity

Pool Total Alkalinity Optimal Levels: 80-140 ppm

Total Alkalinity is closely related to your pool pH levels so balancing out your pH should help in stabilizing your total alkalinity levels. If your total alkalinity is within optimal levels, your pool’s pH levels should be stable as well leading to less pH adjustments down the line. In best practice, stabilize your pool pH levels first, then adjust your Total Alkalinity levels with the same chemicals used to adjust pool pH to lock in your pH levels.

Testing for Pool Calcium Hardness

Pool Calcium Hardness Optimal levels: 200-400

Calcium hardness levels have to be strictly monitored if you want to avoid hard water stains or corrosion to your pool surfaces. In a nutshell, your water needs calcium. If there is too much calcium in your pool water, then that calcium won’t be dissolved in the water and it will stick to your pool surfaces instead, this is apparent when you see hard water stains on your pool surfaces (the white chalk-like stains you see). To lower your pool calcium hardness levels, some people will recommend draining the pool and adding new water or to use flocculants to bind to the excess calcium but we find that too much work as it would entail rebalancing the water again. What we recommend when you’re faced with hard water or calcium levels of over 400 is to use a specially formulated pool chemical to specifically lower your calcium hardness levels like the Zodiac Calcium Down.

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On the other side of the coin, if your calcium hardness levels are below 200 then the reverse will happen. Your pool water will try to look for calcium and the result will be corrosion of your pool surfaces. Concrete, grout, and pool tiles all contain calcium and your water will eat away at them until it reaches a hardness of around 200. To combat this, add a pool chemical like the Zodiac Calcium Up to your pool until your calcium hardness levels fall within the optimal levels.

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Testing for pool Cyanuric Acid Levels

Pool Cyanuric Acid Optimal Levels: 25 – 50 ppm

Cyanuric acid keeps the sun from “eating” your chlorine, that’s why it is also known as pool stabilizers, conditioners, or UV Blockout. The downside to having too much cyanuric acid in your pool is that your chlorine’s sanitizing ability is rendered ineffective and this is why we have to keep an eye out on the cyanuric acid levels. Too much and you’ll have to drain out your pool water and dilute the remaining with new water to bring the levels down.

Too little cyanuric acid (below the optimal levels) and the sun will burn out your chlorine before it gets a chance to clean your pool. To raise your cyanuric acid levels, you can either used stabilized chlorine or UV blockout powders. If your levels are just right, then just use your regular unstabilised chlorine to avoid adding more cyanuric acid to your pool.

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Testing for Pool Chlorine Levels

Pool chorine Optimal Levels: 1-3 ppm

Chlorine is the most important pool chemical in your arsenal. It effectively destroys any microorganism or bacteria in your pool, making it safe to swim in. It’s also one of the most simple ones to balance. If it’s below the optimal level, then simply add more liquid chlorine to raise the levels. If it is too high then just wait it out for a day or two for the sun to eat away at your pool’s chlorine.

There are other ways to lower your pool’s chlorine levels but they’re just an added expense and they will require you to wait a full day as well before using the pool, which is basically the same as waiting it out. Now for indoor pools, the best way to quickly reduce chlorine levels is to drain out some of the water and add new water, but that will require you to rebalance the other chemical levels as well.

There’s another metric known as Breakpoint or Break-Even Chlorination and we’ve tackled that extensively in another blog post, check out the button below to learn more.

Testing for Metal Levels

Metals like copper and iron can come from a variety of sources. The number one culprit for metals in your pools is the water coming from the pipes or corrosion of pool equipment. Many pool testing kits don’t test for metals so you’ll have to buy specialized testing kits from your local pool supply dealer or from online stores. Once you’ve determined that you have high metal levels in your pool, the best way to deal with it is to add a sequestrant to your pool to prevent the metals from staining your equipment and pool surfaces. Sequestrants do not remove the metals in your pool, it simply prevents them from sticking to surfaces.

To remove metals like copper and iron from your pool water, the cheapest and easiest way to do it would to first determine the source of the metal contamination and deal with it there. If the contamination comes from your source water then the best option would be to have a metal-trap pre-filter installed then drain your pool to and then to start from scratch. Chelating metals from your pool water isn’t cost effective is useless if your metal contamination comes from your source water, better to start with clean pre-filtered water and pre-filter all of your future water to prevent metals from entering your pool.

For metal stains, we’ve dedicated a whole blog post on how to identify and remove pool stains and you can check it out by clicking on the button below.

Testing for Pool Phosphate Levels

Optimal Phosphate Levels: Zero

Your pool doesn’t need phosphates, they’re basically pollutants and algae food. Some people don’t bother with testing for phosphates and just treat the water with phosphate removers as a maintenance task. Getting a pool phosphate test kit is optional but it’s a really good way to combat the problem if you detect it early as opposed to waiting for an algae infestation and treating it then. If pool phosphate levels are left unchecked, this may lead to algae blooms and you might even need an algaecide to get rid of the algae that could have been prevented with the judicious use of a phosphate remover.

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Testing for Pool Salt Levels

Optimal Pool Salt Levels: 2,700 – 3,400 ppm

It goes without saying that you only test for salt if you have a saltwater chlorinator. It’s almost impossible to get salt levels above the optimal levels unless you live near a coastal area, but barring that, salt levels are something to be tested once every few months for your saltwater chlorinator to function properly. In many cases, your chlorinator will have a low salt indicator that will tell you when to test and add more salt to your pool. Testing is only done to determine how much salt you should add to your pool. If you go over, then the only way to lower salt levels is to dilute the water with new water.

Putting it all together

Knowing the different chemical levels from testing your pool water is enough in themselves for any pool owner to have a well-maintained pool. If you want to take your pool maintenance skills to the next level, we suggest taking a look at our blog post dedicated to the LSI or Langelier Saturation Index, which will give you a broader understanding of how your pool chemical levels interact with each other and how to achieve perfect pool chemical balance.

Products Featured on This Blog Post

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Conclusion

Our suggestion is to test, test, and test some more. Testing only takes a few minutes but it can save you hundreds of dollars in chemical usage and dozens of hours in maintenance tasks. With pool maintenance, it’s all about knowing what to look for and fixing the problem while it’s small and manageable. Keep both types of testing kits handy at all times. Test strips to monitor your overall chemical levels and reagent kits to get an accurate number right before adding chemicals for treatments. Spend a few minutes every week testing so that you’ll have more time to enjoy your pool and not spend all your time fixing chemical levels from neglect

Do you have any questions about this topic or the featured products? No worries, we're here to help! Drop us a question down below and we'll get back to you ASAP.

Happy swimming :)

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Post author:

Tom Hintze

Head of eCommerce & Operations at Mr Pool Man,
Co-Founder at Water TechniX

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