All the Chemicals You Need for an Above-Ground Pool

Clean Clear Pool with pool chemicals

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Everyone loves a pool with clean water, but how does that water stay clean and not turn green? Pool chemicals are what keep your pool clean and clear. Understanding the essential pool chemicals is key to taking good care of your pool. Besides keeping your pool from turning green, pool chemistry helps protect the finish of certain types of pools and can extend the life of your pool machinery and plumbing.

In this guide you can learn what each pool chemical does and how they work together to help maintain your pool’s chemical balance and clean appearance. Here are the four essential pool chemicals.

The Four Pool Chemicals

Chlorine, pH, alkalinity, and calcium all work together to help maintain a picture perfect pool. Each one of these chemicals has a unique role to play in the daily maintenance of all pools. Chlorine fights bacteria; pH controls pool acidity and promotes chlorine effectiveness; alkalinity helps maintain pH levels; and calcium helps maintain the Alkalinity. Checking each one of these chemicals weekly and adjusting accordingly will ensure a perfect pool for many years to come.


Chlorine is the main bacteria-fighting chemical responsible for sterilizing the pool water so no bacteria can grow. It’s the chemical you most likely associate with pools, though bromine and salt are two common alternatives that work in a similar fashion.  

Chlorine should be checked weekly, at a minimum. Keep in mind that, for chlorine (and any other chemical added to your pool), if your pool gets a lot of sun, rain, or debris from the surrounding area the water will use up more chemicals to maintain the balance, so check the balances regularly to eliminate any surprises from that recent rainstorm or heat wave.

When adding chlorine to your pool remember that chlorine bleaches (it is a form of bleach, after all) and in strong enough concentrations over time can make plastic brittle. This is why it is important to add chlorine in a float or through a chlorinator, which will help evenly disperse the chlorine and mitigate the risk of bleaching.


Never place chlorine tablets at the skimmer mouth. The chlorine tablets’ close proximity to the pool machinery will shorten the life of the pool components it comes near.


PH level is another more common chemical level that gets monitored weekly. The purpose of checking the pH level is to make sure the water is not too acidic or basic so that the chlorine is able to properly kill bacteria but it is also safe for swimming and contact with skin.

If the pH level is too high or low, there are commercial powders for sale that can help adjust the pH level.

PH level is also important to monitor because if the water is too far in either direction it can cause damage to your pool machinery. An example of this would be the pool water eating through plumbing lines or damaging the internals of your equipment such as seals, or plastic or metal pieces, not to mention what it would do once in contact with a person’s skin.


Alkalinity is a pool chemical that is often overlooked but is still just as important as chlorine or pH. Alkalinity is responsible for stabilizing the pH level, which helps the chlorine to do its job.

A low alkalinity level will cause the pH level to fluctuate, which would hurt the chlorine’s ability to keep the pool clean and can damage your machinery or hurt someone in the pool.

A high alkalinity level will make the water feel slippery, cause scaling, and make your water look cloudy. Alkalinity is generally checked every two weeks, but it does not hurt to also check when testing the chlorine and pH levels to help diagnose out-of-range chemical readings.


Calcium is another pool chemical that is often overlooked. Calcium helps mitigate calcium stains on hard surface pools while stabilizing the alkalinity level.

If your pool has low calcium then it is at risk of destabilizing the alkalinity, which helps stabilize the pH level, which promotes the effectiveness of chlorine.

On the other hand, if your pool has high calcium this can cause scaling on your pool’s floor, wall, and piping and prematurely corrode metal fittings and fixtures. Calcium levels in a pool should be checked every two weeks, but again is beneficial to check every week to help diagnose other issues that the pool might be having.