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Pool Water Chemistry 101: A Beginner’s Guide

Pool Water Chemistry

Pool water chemistry is not the topic of many idle daydreams. Everyone would love to install a swimming pool, fill it with water, and not have to worry about bacteria or algae. It takes time to balance pool chemicals, and many people find the task annoying. However, maintaining swimming pool water chemistry is essential to protecting your investment and ensuring a healthy backyard experience. 

A homeowner can clean and sanitize their pool appropriately. You will just need some basic equipment and supplies. 

As noted by Matt Harper of Pool Care Guy, the most important task you could have as a pool owner is maintaining chemistry. Harper notes that using sanitization best practices and well-balanced pool water chemistry keeps the water safe for swimmers: clear and beautiful. 

What You Need to Know About Swimming Pool Water Chemistry

Pool Water Chemistry Calculator

Pool owners often seek an online calculator in which to run numbers. The tools available online are not comprehensive but can be useful for what they are:

Chemical Factor Levels

Three key factors in pool water chemistry are pH, alkalinity, and calcium hardness. Here are the recommended levels and why it is important to keep your pool within the advised range.


Recommended level: 7.4 to 7.6

Your pool’s pH level indicates how acidic the water is.

The level matters because if it’s:

  • too high, you can get scaling on the plumbing & surface; or
  • too low, metal fixtures could erode, or etching could appear on your pool’s sides.

Recommended level: 100 to 150 ppm

Your pH level should be as stable as possible. Alkalinity supports stability by regulating potentially destabilizing factors. 

Calcium hardness

Recommended level: 150 to 400 ppm

A proper calcium hardness level keeps your pool surface attractive and maintains your water cleanliness. 

If your calcium levels gets:

  • too high, your filters and plumbing could end up with scaly deposits while your water gets cloudy and hard; or
  • too low, there will be sliminess to the water, which will begin leaching calcium from the surface of your pool.

Sanitizing Chemical Levels

Sanitizing is the top-priority concern of swimming pool water chemistry. Most people use chlorine to sanitize their pools for its affordability and effectiveness. However, a couple of other sanitizing chemicals are also worthy of mention.


Recommended level: 3 ppm

Chlorine is incredibly affordable and effective, making it the #1 pool sanitizer. Chlorine oxidizes anything that is contaminating the water. It invades molecules of algae, bacteria, and viruses; then, it destroys them from within. Plus, chlorine prevents the initial growth of algae.

If the level is:

  • too high, you will need to get the chlorine level down with a chlorine neutralizer or through dilution with more water. 
  • too low, your pool water should not be considered sanitary and clean. 

Two basic options you have for chlorine are:

#1. Tablets — You can introduce tablets (1-inch or 3-inch versions) into your automatic chlorinator, into your skimmer basket, or into a floating chlorine dispenser. Doing so will save you time, you will not have to handle tablets as frequently, and you get an ideal dispersion rate. 

#2. Granules – With this method, granules of chlorine dissolve and pump into your pool water, where they are distributed via the filtration system. This method is not best for chlorination: 1.) It may result in imbalanced distribution of chlorine, causing your pool liner to become damaged due to super-chlorinated areas and resulting in spots that are ineffectively sanitized; and 2.) It can eat up a lot of your free time.


Recommended level: 3 to 5 ppm

An alternative to chlorine, bromine is used to reduce the strong smell. It is used for indoor pools and hot tubs in some cases for that purpose.

Bromine is not a good choice for outdoor pools because it does not fare well in the sun. It is also generally less effective than chlorine.


Recommended level: 30 to 50 ppm

Biguanide is a costlier but similarly effective chlorine alternative.

You need to use a matching pool shock and algaecide because biguanide cannot be blended with other chemicals.


Pool owners often choose ozone because it does not have a strong smell and is praised for their skin gentleness. To ensure sanitization of all your pool water, you may need to supplement the action of your Ozonator with a small amount of chlorine.

Additional Pool Water Chemistry Supplies

You can typically keep your pool in good shape using chemicals to sanitize your pool, maintain safe alkalinity, balance pH, and manage calcium hardness. However, additional chemicals may be needed to prevent and treat cloudiness, algae, and stains. 

  • Clarifier and flocculant – Clarifier is used to immediately do away with cloudiness. It temporarily clears the pool. Flocculant is a permanent solution, creating clumps of the problematic material that must be vacuumed from the bottom of the pool.
  • Algaecide – If you develop algae, along with a double- or even triple-shocking with chlorine, you may need an algaecide. 
  • Metal sequestrant – You may see green or rust-colored stains develop if copper or iron is in your water. These stains will require cleaning. Metal sequestrants can be used to keep stains from recurring.

Chemistry Of A Saltwater Pool

Your swimming pool water chemistry needs will be different if you have a saltwater pool. Here are cornerstones of saltwater pool chemistry:


Recommended levels: Usually about 3400 ppm

A salt chlorine generator will generally need salt to be at about 3000 ppm to operate. You may have to add salt to get the level to the generator’s minimum. 


Recommended level: 7.4

Your pH will change as time passes and will, overall, keep rising in saltwater pools. Take steps to lower the pH when it gets high, as detected by regular checks.


To stop chlorine from evaporating, cyanuric acid is typically used as a stabilizer in saltwater pools. Your chlorine level should be stable when you have the correct amount of stabilizer.

Free chlorine 

Recommended level: 1 to 3 ppm

Use a test kit to check your chlorine. When additional chlorine is needed, you can shock the pool with granular chlorine. Expect to occasionally take this route to get the chlorine to a safe level and adequately defend swimmers against contaminants. Pay careful attention to the manufacturer’s instructions.

Water Chemistry

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