Pool Chemistry for Dummies

Ryan Cuenca
November 19, 2018

If you've mastered the art of testing your pool water, you are ready for our next course: Pool Chemistry for Dummies.

For starters, I'm assuming you are here because you need help with some pool water issues.  That is, you want to know what to do to maintain balanced pool water, and care less about the theory of pool chemistry.  On the other hand, if theory is your thing, here is a great piece for you to read.

With this in mind, I wrote Pool Chemistry for Dummies as a no-nonsense action guide on how to correct water balance issues you might be having.

IMPORTANT: The information below assumes you know how to test your pool water.  If you don't, I suggest reading our article here before continuing.

Hopefully, you are already using our free online pool chemistry calculator to make sense of your pool water chemistry levels. It works with just about any test strip or test kit on the market, and we built-in simple user interfaces to match up with some of the most popular pool water test kits from LaMotte, Clorox Pool & Spa, and Poolmaster.

Now...let's dive into Pool Chemistry for Dummies!

Pool Chemistry for Dummies: A How-To Guide

Proper pool chemistry requires two main ingredients: Water Balance & Sanitation.  (Of course, it also includes Circulation & Filtration, as we describe here.)

Water Balance

There are 4 central elements in Water Balance:

  • pH
  • Total Alkalinity
  • Calcium Hardness (aka Hardness)
  • Cyanuric Acid

In the following sections, I'm going to tell you the ideal range for each element, based on your test strip result, and what to do if the element (pH, Alkalinity, Calcium Hardness, Cyanuric Acid) is too high or low.


Ideal Range: 7.2 - 7.8.  No action required.


  • Lower than 7.2: Add a pH increaser*
  • Higher than 7.8: Add a pH decreaser (or muriatic acid)

*Read "The Curious Case of Low pH and High Alkalinity" below for an exception to this rule.

Total Alkalinity

Ideal Range: 80 - 120 parts per million (ppm).  No action required.


  • Lower than 80 ppm: Add a Total Alkalinity Increaser
  • Higher than 120 ppm*: Add pH decreaser (or muriatic acid)

*Read "The Curious Case of Low pH and High Alkalinity" below for an exception to this rule.

Calcium Hardness

Ideal range: 150 - 400 ppm.  No action required.


  • Lower than 150 ppm: Add Calcium Hardness Increaser
  • Higher than 400 ppm and:
    • Your source water has high hardness*, use a mineral removal agent (aka Stain and Scale, mineral sequestering agent)
    • Your source water has low hardness*, "dilution is the solution"** (i.e., drain some of your pool water and add freshwater)

*Hardness is the amount of calcium in your water.  To determine source water hardness, follow the instructions in our article here, but test the water you use to fill your pool instead.

How to Dilute your Pool Water**

To properly dilute your pool water, follow these instructions:

  1. Ensure your pool equipment is OFF.
  2. Empty 1 - 2 feet of water from your pool.
  3. Refill the pool until water is halfway up your skimmer opening(s).
  4. Turn your pool equipment back ON and run your filter pump for 6 - 8 hours.
  5. Re-test water.  Repeat from step 1 if necessary.

Cyanuric Acid (CYA)

Cyanuric acid is added to the most popular forms of chlorine.  Its job is to protect the chlorine from being dissipated too quickly by the sun's ultraviolet rays.  Think of it as sunscreen for the chlorine.

However good this sounds, it comes with a cost, namely that it can build up in your pool over time and prevent your chlorine from doing its job.  It can also interfere with your Total Alkalinity readings.

Ideal Range: 20 - 100 ppm.  No action is required.


  • Lower than 20: Add Cyanuric Acid (aka water stabilizer)
  • Higher than 100: Dilution is the solution**

The Curious Case of low pH and High Alkalinity

In extremely rare cases, one will receive a low pH and a high Alkalinity result.  Here's what to do when this happens:

  1. If you have new pool water, let it settle in for a few days and retest. Sometimes, this issue resolves itself.
  2. Increase your pH using a pH increaser so that it is well above 7.2.
  3. Lower the Total Alkalinity by adding pH decreaser or muriatic acid (do not let pH drop below 7.2)
  4. Increase the pH by adding pH Increaser until you reach the ideal range.

If your pH, Total Alkalinity, Calcium Hardness, and CYA readings are within the ideal ranges stated above: Congratulations, you have balanced water!  If not, take the corrective action provided until your water is balanced.

Water balance is important for a number of reasons.  One of these reasons is that it allows your sanitizer to work at an optimal level.

On to sanitation!


There are 3 main types of sanitizers used by pool owners today: chlorine, bromine, and biguanide.

Please note that if you own a saline pool, your pool is still a chlorine pool.  The difference is that your salt water chlorine generator creates it so that you don't have to add it regularly.

I'm going to tell you the ideal range for each chemical.  The corrective action for each type of sanitation is straightforward (this is Pool Chemistry for Dummies, after all!).  If your water test reading is low, add more sanitizer until it reaches the ideal range.  If it's high, do not add more sanitizer until it drops to the ideal range over time.

Regular Use Sanitizers

  • Chlorine: 1 - 3 parts per million (ppm)
  • Bromine: 3 - 5 ppm
  • Biguanide: 30 - 50 ppm

The proper amount of sanitizer is necessary to kill algae and bacteria in your pool and keep your water looking clear.

Irregular Use Sanitizer: Shock

Pool shock is simply another word for a highly concentrated and effective shot of chlorine to your pool.

Some recommend a weekly dose of shock.  This recommendation is suitable for some, but not for all.  In Pool Chemistry for Dummies, we advise shocking your pool:

  • 1 day prior to and after a large pool party
  • When you let your sanitizer run too low
  • When your pool is green or turning green

Additionally, here are some situations when you don't need to shock your pool:

  • If you winterize your pool
  • Outside of swim season, when the days are shorter, the temperatures are cooler, and the pool isn't being used

Other Important Water Balance Elements

So, your water is balanced and sanitized.  That's all there is to it, right?

Yes, for the vast majority of pools.  Maintaining proper levels of pH, Total Alkalinity, Total Hardness, CYA, and Sanitizer will be adequate for clear, clean (safe), pool water in most cases.

However, I would be remiss by not pointing out a few special circumstances that require additional tests and corrections.


Certain metals, namely iron, copper, and manganese, can make their way into your pool water.  If their presence is strong enough, bad things can happen (staining of your pool finish, green pool water, and green hair, to name a few!).  More importantly, at elevated levels, they can be outright toxic to people!

To test your water for these metals, we recommend taking a sample of both your source water and your pool water down to a pool store for testing.  (Or, become a Poolhop subscriber, and we'll test your water for you.)

If either sample has high metal content, the solution is a metal remover product (aka Stain & Scale).  Now, if your source water has high metal content, then the metal remover must be made part of your regular chemical dosage plan.

Total Dissolved Solids (TDS)

Of the two special cases mentioned thus far (metals & cyanuric acid), total dissolved solids are usually the cause of least concern. But they can prevent your sanitizer from working well, and can also result in perpetual cloudy pool water, so I'll give a quick solution.

First, the best way to test TDS is to take a pool water sample down to your local pool store.

Ideal Range: 0 - 2000 ppm


  • Lower than: N/A, no lower limit
  • Higher than 2,000: Dilution is the solution**

Some Closing Thoughts

"Now is my water balanced?", you may be asking.  To which my response is a resounding yes!

If your pH, Total Alkalinity, Total Hardness, CYA, Sanitizer, metals, and TDS levels are all within the ideal range your pool water is most certainly balanced.

This, combined with proper circulation, filtration, and maintenance will result in beautiful pool water.

One final note: As you probably noticed, we intentionally did not make any specific product recommendations in this article.  There are many fine suppliers of pool chemicals.  And, as is often the case with consumer goods, the essential ingredients are the same across different brands.

So if you need to buy a pH increase, for example, most pool stores and online retailers will provide a quality product.  If you have any doubts, please contact us and we'll help you out!

If you really want to kick this pool care thing into high gear, check out our free DIY Pool Maintenance Plan tool. In about 15 seconds, you get a list of all the sanitization chemicals needed for the entire year. It doesn't matter if your pool is above-ground or in-ground, or if you maintain it year-round or seasonally. The maintenance plan is built to the exact specs of your swimming pool.

Lastly, whatever product(s) you end up purchasing, always make sure to follow the manufacturer's Directions for Use.

Thank you for reading Pool Chemistry for Dummies.  Comments are welcome below!

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