Saltwater Pool Chemistry (What is different?)

A common questions we get is how do you maintain a salt water pool? Or, what is the ideal water chemistry for saltwater pools? We'll talk about the most important things to know about salt pool maintenance and the top ten most important chemistry levels for pools with saltwater chlorine generators .

Is the water chemistry different for saltwater pools versus traditional chlorine pools? The basic answer is no, there is just the salinity level of the water which is added to the mix. Water chemistry maintenance is typically easier with a salt pool, since your chlorine level (which is what usually would fluctuate the quickest) is maintained and the salinity level of the water remains fairly constant. Below are the top ten chemistry levels for saltwater pools, they are based on national standards and although it might not touch on every last thing there is to know, it will give you a pretty great start.

1. Free Chlorine

What it is - Free Chlorine (FC) is the leftover residual of sanitizer that keeps your pool clean and safe to swim in. If chlorine is added to the pool and you don't measure any FC, that means that there are enough impurities that the added chlorine has been completely used up and there wasn't enough leftover to create the measurable residual.

Why it is important - A constant level of FC means that there is active sanitizer "waiting around" in the pool, ready to attack impurities as they enter the water. If your FC doesn't stay in range, that means that impurities like bacteria and algae can get a head-start on you and begin to grow and multiply in the water. FC is consumed not only by those impurities, but by the sun as well. Basically what that means that the FC is constantly being consumed unless more and more chlorine is being added to the pool (Which is what salt systems do for you. Nice!) .

Ideal levels - The ideal FC level varies, especially with your CYA level, but in general you want to keep your FC between 1-3 ppm in a saltwater pool.

2. Salinity

What it is - Salinity is how much salt is present compared to how much water is present, or in other words, the level of salt in the water.

Why it is important - Salt itself is not a sanitizer. Salt pool systems need a certain level of salt in the water to be able to operate and create chlorine. When salt levels are too low (and for some systems, too high), the process of generating chlorine is much less efficient and it puts much more strain and wear-and-tear on the chlorine generator's cell. Remember that salt doesn't get used up in the process. You only need to add more salt because you have drained water out of the pool or you have gotten a lot of rain (adding water for evaporation doesn't count). Since its levels don't naturally go down, remember to test, double-check, and add salt in batches so you don't add too much.

Ideal levels - Check your system's manual, but for most systems the ideal salinity range is right between 3000 - 3500 ppm.

3. Acidity / pH

What it is - pH is the balance of whether the pool is acidic or basic.

Why it is important - An imbalanced pH has pretty far-reaching repercussions. You chlorine will be less effective, requiring higher levels of chlorine being added to the pool. The water can become much more harsh on your skin and eyes. Imbalanced pH can even lead to damage to your pool itself and equipment. With experience, you'll see how your pool's pH wants to trend, and maintaining the pH can even become rather infrequent.

Ideal levels - pH levels typically want to be kept between 7.5 and 7.8 on the scale. Remember that small changes on the pH scale can add up to large results.

4. Stabilizer / Cyanuric Acid

What it is - Cyanuric Acid (CYA) is a conditioner chemical that helps prevent the sunlight from breaking down chlorine in the water.

Why it is important - CYA is often called "sunscreen" for your chlorine. It is very important to have CYA in your pool water. However, as CYA "coats" the chlorine, it also begins to make the chlorine a less effective sanitizer. That means it is also very important that you don't have too much CYA in your pool water. It is also important to know that CYA does not break down, which means that if you add too much, the only way to lower the CYA level is to drain large amounts of water from your pool to compensate.

Ideal levels - If you don't have an extremely high amount of sunlight, CYA is typically kept between 30 and 50 ppm. With high levels of direct sunlight, CYA is typically kept as high as 70 and 80 ppm.

5. Phosphates

What it is - Phosphates are, unfortunately, very common substances that accumulate in pools and other bodies of water. They come from both natural and man-made sources. A very concentrated source of phosphates is fertilizer, however it is also a persistent part of our environment as well.

Why it is important - Phosphates create an EXTREMELY high chlorine demand in the water. Since phosphates don't break down naturally, the problem will only get worse until it is treated. High phosphate levels could potentially raise the chlorine demand of the water past the ability to add enough chlorine to compensate. Phosphates also allow algae to grow even with chlorine in the water.

Ideal levels - IDEALLY ZERO if possible, otherwise as far under 100 ppb (parts per BILLION) as possible.

6. Total Alkalinity

What it is - Total Alkalinity (TA) is the pool water's ability to "buffer" pH changes, or in other words, to make it easier or harder for pH to change.

Why it is important - TA balance can cause you need to use a larger quantity of a chemical to change the pH, or allow there to be rapid swings of pH. TA also determines the LSI which helps prevent pool damage or calcium scaling.

Ideal Levels - Typical TA levels fall within 100-200 ppm.

7. Calcium Hardness

What it is - Simple enough, Calcium Hardness (CH) is the level of calcium based minerals in the pool water.

Why it is important - Imbalanced CH can lead to corrosion or damage to plaster or concrete, and excessive scale deposits.

Ideal Levels - It may vary with your pool type, but in general 200 - 400 ppm.

8. Saturation Index

What it is - The Saturation Index (SI) is the measure of the water's tendency to become corrosive or scale forming.

Why it is important - the SI balance takes into account other chemistry levels such as pH, CH, TA and more. A low SI means that the water wants to absorb things into it and causes corrosion damage. A high SI means that the water wants to deposit things out of it and causes high levels of mineral scaling.

Ideal levels - The SI is kept between -0.2 to +0.2. The SI is measured on a small scale, with a one point difference indicating an effect in reality being 10x as severe.

9. Nitrates

What it is - Nitrates, like phosphates, are a powerful food source for algae. Nitrates, however, are not as common in pools, unless introduced through fertilizer-based sources.

Why it is important - Nitrates cause very high chlorine demand in the pool water, don't break down naturally, and can't effectively be treated. Significant nitrate levels in the pool require it to be drained.

Ideal levels - Zero if possible

10. Other contaminants

What it is - Contaminants such as metals (copper, iron, etc...) and ammonia

Why it is important - These contaminants can make it harder to balance your other chemistry levels, cause high chlorine demand, and even stain pool surfaces.

Ideal levels - Zero

TIP: Check your chemistry levels frequently when you first install a saltwater chlorine generator. With experience, you'll find out the way your pool water tends to behave, and fairly quickly discover that your chemical maintenance needs have been greatly, greatly reduced.

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Date 7/22/2018

What chlorinator would be best? Could I use normal Salt water treatment chemicals Cyanuric acid, Muriatic acid and Algeacide etc..?

DSP Staff

Date 7/23/2018

Brian, You typically want a salt chlorinator that can handle at least 50% more gallons than your pool holds. You initially just add regular pool salt or water softener salt (Sodium Chloride) to start up when you install the system, and you'll balance all of your other supplementary water chemistry as normal, like you mention - nothing else changes or requires special chemicals.

Michael Sheehan

Date 5/25/2024

Test strip shows low chlorine level in pool. We are only running the chlorine generator at 25%. If we raise it to 50% will that raise the chlorine level.

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