Ideal Chemical Levels for Swimming Pools

It would be nice if you could just fill your swimming pool with water and go for a swim. But, unfortunately, doing that will mean your pool grows nasty algae, builds up bacteria, and overall becomes a breeding ground for all sorts of unwanted organic contaminants.

It might seem tedious to constantly test your water and add chemicals, but it’s essential for your health and the safety of your pool water.

Doing regular maintenance and maintaining proper chemical levels in your pool will avoid time-consuming cleaning processes down the line. If your pool becomes infested with algae, for example, there’s little to do but drain the water and start from scratch.

Unfortunately, this process will render your pool unusable for several days, so it’s much better to stay on top of maintenance and enjoy your pool whenever you want.

Keeping your pool chemicals at the right level doesn’t have to be complicated. It’s not necessarily fun, but with a bit of knowledge of basic pool water chemistry, the right supplies, and a regular maintenance schedule, you can keep your pool water crystal clear and ready for swimming!

Ideal Chemical Levels for Swimming Pools

The Basics of a Clean Swimming Pool

Even if you skim, filter, and vacuum your pool daily, your water will still get dirty without chemical intervention. Leaves and dirt blow into the pool. Bugs swim or drown in it. Birds fly over and poop in it (gross, but true).

Every time you go for a swim, you leave body oils behind; hair, dead skin cells, deodorant, soap residue, and shampoo all leave microscopic particles behind in your pool water.

Your pool water isn’t already growing creatures from the black lagoon because you use sanitizing chemicals. Pool sanitizer is the most essential pool chemical you will ever use. However, it requires certain conditions to work effectively, such as a balanced pH level, alkalinity, and calcium hardness.

Other categories of pool chemicals include algae treatments, clarifiers, and stain prevention. There are some chemicals to keep buildup out of your filtration system if you have hard water, as well.

Knowing what chemicals to use when (or whether you need some at all) will allow you to create balanced, clean, safe water in your swimming pool.

Pool Sanitizer

No matter which type of sanitizer you choose, a pool sanitizer’s job is to sanitize your pool. It keeps your pool water free from bacteria, viruses, algae, and other nasty particles that grow unchecked in water that isn’t treated. There’s more than one option for pool sanitizer chemicals, so let’s look at your choices.


Chlorine is the most popular sanitizer chemical for swimming pools and the most well-known. It is good at its job and relatively cost-effective to use. Chlorine oxidizes contaminants in your pool, meaning it sneaks into molecules and destroys them. It kills bacteria, viruses, and algae and even prevents them from growing to start with.

There are two different forms of chlorine:

  • Granules are poured into your filter and pumped out directly into your pool. Granule distribution of chlorine is time-consuming as the chlorine is often unevenly distributed, leaving some parts of your pool over-sanitized and others not sanitized at all. The purpose of granules is most often when you start new pool water and need to increase chlorine levels quickly or shock your pool. Usually, you will want to follow up granular chlorine with a form that maintains chlorine levels, like tablets.
  • Tablets or pucks are available in different sizes and added to a floating dispenser, a skimmer basket, or an automatic chlorinator. They are slow-release tablets and designed to maintain your chlorine levels over time without continuously adding chlorine.

Ideal chlorine levels in your pool should be three ppm. Less than that, and your pool’s not clean. Higher than that will cause serious irritation while swimming.


Bromine is a readily available alternative to chlorine and works by ionizing contaminants instead of oxidizing them. Ionization means that bromine breaks apart the chemical bonds that make up contaminants.

The number one benefit of bromine over chlorine is that it remains active for a more extended period. However, bromine pools still require occasional shock, and bromine is available in granular and tablet forms like chlorine.

Your pool water should have a bromine level of 5 ppm and should not be allowed to drop below 3 ppm.

Biguanide of PHMB

Your final option for pool sanitizer is a biguanide, a surgical disinfectant similar to hydrogen peroxide. Biguanide works by binding contaminants together into insoluble clumps that the filter can pick up. The biggest downside to biguanide use is that your filter will clog and require more frequent cleanings.

So, if it clogs your filter, why would you use it? Biguanide doesn’t produce chloramines (the nasty smelling byproducts of chlorine breakdown), it’s gentle on your skin and eyes, it doesn’t break down in sunlight, and it won’t turn blonde hair green in the pool.

Biguanide is the most expensive type of sanitizer and breaks down over time. It can also make your pool water cloudy, so do your homework before switching to this type of sanitizer.

Ideal levels of biguanide in your pool are between 30 and 50 ppm. Below 30 ppm, your pool has zero effective sanitization.

pH Levels

The pH scale measures the degree to which a substance is acidic or basic. It’s measured on a scale of 0-14, with 0-6.9 being acidic and 7.1-14 being basic. 7.0 is considered neutral on the pH scale.

Your water may have a pH higher or lower than 7, and the pH is further altered by anything that enters the water. Rainwater, people, dirt, everything will either raise or lower the pH of your water. This is why you have to monitor your pH levels and adjust them with chemicals.

There are two pool chemicals (or maybe 3) you will need to adjust your pool water’s pH. These chemicals are pH increaser, pH decreaser, and if you have very alkaline (basic) water, you might consider muriatic acid.

Ideal pH levels for pool water are somewhere between 7.4 and 7.6, so slightly on the basic side. At this level, chlorine and bromine work at optimum levels.

Note: The purpose of using muriatic acid is to lower water pH with less chemical. If you have very alkaline water, it takes significant amounts (think the whole bottle) of pH decreaser to get your pH at the optimum level.

In contrast, you would only require 2-3 capfuls of muriatic acid. If you are using muriatic acid, be very careful! It is, as the name implies, an acid that can cause burns to your skin.


You may have noticed that your pool test strips have one reading for pH and another for total alkalinity. What’s the difference? Constant total alkalinity levels act as a buffer for your pH and keep it from bouncing around too drastically.

If you have an acidic pH in your pool water, you can use either a pH increaser or baking soda to correct it. If both your pH and alkalinity are low, you would still use the same chemical. Adjust your total alkalinity levels first, and the pH will follow.

It can take a little fiddling to get your levels right. Make your adjustments gradually to avoid throwing things drastically out of whack. As stated before, if you find your alkalinity is incredibly high and not budging with a pH reducer, try muriatic acid.

The alkalinity levels in your pool should be 100 ppm to 150 ppm. If you must run high or low on this scale, it is best to run on the high side.

Calcium Hardness

Whether you have hard or soft water, this indicates how much calcium is present in your water. Hard water has lots of calcium, whereas soft water has little or none.

High calcium levels in your water cause scaling and buildup on your pipes. These levels can be reduced by shocking your pool, adding a clarifier, or adding flocculent. Most commonly, you will notice that you have cloudy water. It’s not harmful to swimmers, just not as clean-looking.

If you have very soft water, you will have a low calcium hardness reading. The topic of whether you need to add calcium to your pool is a little controversial, but we’ll give you an overview.

You can buy a calcium hardness increaser to add to your water and bring calcium levels up to ‘normal’ at a level of 175 ppm to 225 ppm. There are pool maintenance companies that will tell you that having low calcium leads to scaling and corrosion in your pool.

However, as a rule, it is hard water that causes scaling and corrosion, not soft water. People spend thousands of dollars to equip their pools with saltwater systems that create soft water that is less damaging to both swimmers and the pool itself. The decision of whether to add calcium to your water is your own.

Happy Swimming!

Knowing what pool chemical you need and how much you need can make pool maintenance a breeze. Don’t let the process of adding chemicals be intimidating. Most test strips will clearly indicate normal ranges so that you don’t have to guess. Test your water every week and add chemicals as needed to maintain clear water all summer.

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