Saltwater Pool Chemistry

Salt Water Generators or pool salt systems, create chlorine from electrolysis of a saline solution. In the process of making your own chlorine, chemical reactions occur that aren’t present in tablet chlorinated pools.

The Topic of Discussion today is pH Rise, Corrosion and Cyanuric Acid; in a salt water pool.

pH Rise in a Saltwater Pool

ph-rise-in-a-salt-water-pool

In a salt pool, when electrolysis occurs (within the pipe), the products are hypochlorous acid, which is very acidic (as you may assume), and sodium hydroxide which is very basic. However, the acids and bases created by your salt cell will neutralize each other with very little net pH change.

The pH rise noticed by some salt chlorinator users may be a result of the outgassing of carbon dioxide, as water is agitated through the salt cell with hydrogen production.

A simpler answer is that Trichlor tablets, which have a very low pH, tends to suppress pH levels, or drive them lower over time, and in their absence, pH levels will naturally drift higher.

Corrosion in a Salt Pool

Salt is a corrosive substance, which is why winter road salt creates problems for concrete and steel.

Salt levels in a salt pool are usually quite low, under 3500 ppm. But even at low levels, galvanic corrosion can occur to stainless steel equipment (filters, lights, ladders) that is not properly bonded. Passive corrosion can affect soft porous stones and concrete around the pool.

sacrificial-anodes-for-salt-pools

What to do? One solution is pool equipment made of thermoplastics or bronze, or you can slow galvanic corrosion with a sacrificial anode. Zinc anodes attach to ladder, pool light or skimmer, and self-sacrifice, to draw corrosion away from other metal sources with lower electrochemical potential.

Cyanuric Acid in a Saltwater Pool

You didn’t know that you have to use cyanuric acid (Stabilizer or Conditioner) in a salt pool? In fact, you should use more than pools that chlorinate with Trichlor tablets. Hayward and Pentair both recommend 60-80 ppm of cyanuric acid for their salt systems.

Why more CYA? Manufacturers of salt systems want more output from the salt cell, without fighting against UV degradation. As cyanuric acid bonds to chlorine, the chlorine residual can build faster.

However, when using high range CYA levels, above 50 ppm, you must also maintain a higher Free Chlorine level, in the range of 5 ppm, to compensate for the effects of cyanuric acid on chlorine.

cyanuric-acid-compensation-chart-for-chlorine - Intheswim Image

What effects? Cyanuric acid protects chlorine from the sun, but it also restricts chlorine activity; reduces kill rates and impacts ORP. As a result, many public pools are raising their FC minimum, for pools treated with cyanuric acid, or stabilizer. See an earlier blog post on chlorine kill rates in pools.


In a nutshell, water chemistry of salt water pools is not much different than tablet chlorine pools. Here’s the key takeaways from the discussion.

  • Maintain your pH at 7.4-7.6 and Total Alkalinity at 90-110 ppm
  • Invest in a Sacrificial Anode for metal equipment or soft stones
  • Test and Adjust Cyanuric Acid to manufacturer recommendation

26 thoughts on “Saltwater Pool Chemistry

  1. Good morning, I have a new 31,000 gallon pool that I transitioned to my salt cell after the 30 day start up. All of my levels are ideal except I cannot get my chlorine levels up. CYA is currently at 60 while my FCL and TCL are both under 1. I have been running the cell non-stop the past two days hoping the chlorine levels would get to the proper levels, but they are not. What should I do?

    • Hi Keith, I would say that you may have high levels of ammonia or nitrates in the water, consuming the chlorine, and would suggest a triple-shock, using 9 lbs of granular chlorine, to destroy those substances. Also be sure to drop the pH level first, down to around 7.2-ish, where chlorine is most potent.

  2. Eric D Denner

    I’m setting up a 3400 gallon saltwater pool for my granddaughter, and was wondering what i should keep the salt level at and how much cyanuric acid to add.

  3. Hi, I have a small above ground pool (1000 gallons), but with sand pump filter and saltwater. Recently it got algae, so I emptied the pool. My question is how I clean the pump?

    What is the correct procedure to initiate the pool? Add salt and at the same time CYA?

    Thank you very much
    first-time pool user

    • Yes, you can add salt, and brush to help dissolve it. Then add cyanuric acid. Keep some granular chlorine (shock) on hand, to raise chlorine level very high on occasion, and also use a weekly dose of Clarifier and Algaecide, to help the small filter and salt system. You can also just abandon the salt system and start using 1″ tablets in a chlorine floater.

  4. Colleen Hubley-Kedinger

    We just put our pool up for the first time. We have a saltwater system for our 5400 gal pool. Do I need to put a chlorine stabilizer (cyanuric acid) in the pool that is specifically for saltwater systems or can be a general chlorine stabilizer? Is trihydroxy-s-triazine the same as cyanuric acid?
    Thanks!

    • Hello, trihydroxy-s-triazine is another name for cyanuric acid. You should add stabilizer for a salt system yes, to prevent your salt cell from overworking. I don’t know of a CYA that is made for salt pools.

  5. Hi there! We just got a 26 ft, 15,000 gallon intex above ground pool. We have a sand filter and added a saltwater system (pool is still filling so it’s not even been run yet). When we get it filled and add our salt in, should we go ahead and add the stabilizer at that point? Or does the pump need to run the recommended 24 hours and then we test and add? I read a few places that 4 lbs would be needed for the initial startup? There’s so many differing opinions everywhere so I’d love any advice! Wasn’t sure how often stabilizer needs to be added either, first time owners here just trying to be sure we get it right and have clean water to swim in!

    • Stabilizer: Use 1 lb per 10,000 gallons, to raise the level by 10 ppm. For your pool, about 4 lbs would be fine, 30-50 ppm is the best target level. Stabilizer does not deplete, so you will only need a booster amount added next season.

  6. Bobby Warren

    I have a 28000 galkon pool and my cyneric acid level is low….how much acid per 10000 gallons should I add?

    • Hi Bobby, the rule of thumb is to add 1 lb per 10,000 gallons to raise CYA 10 ppm, but check the label to be sure. Recommended level is 30-50 ppm.

  7. Glenn Thoma

    I have a 8000 gal pool with a cya of 110. I believe this makes my salt cell work harder. I live in Florida and run my pool all year. My questions. Will this high level harm a swimmer? The only way to lower the level is to drain my pool and refill,correct? If I am willing to accept the heavy cell usage can I leave the cya at this level without harm to swimmers and pool surface? I find I can’t get the cya down because I am always fighting the high on level. Thanks in adavance

    • Hi Glenn, such high levels make chlorine less active, and less potent. At a level of 110 ppm, you would need to keep the chlorine level about 5 ppm, to maintain sanitary water, or water that is fully disinfected. This can make the salt cell work harder, to keep such a high level of free chlorine. Since your pool is so small in size, I would recommend draining and replacing 1/4 of the water, or 1/3 even, to get the CYA level down to 60-70 ppm range, which most salt system manufacturers recommend (although we normally like it lower, 30-50 ppm, around here…). There is no solid evidence that cya is damaging to swimmers or pool surfaces, although some believe that it may. High levels have been shown to be carcinogenic in lab mice.

  8. From the Pentair IntelliChlor user manual: “When using the IntelliChlor SCG, thecyanuric acid level should be maintained between 30-50 ppm”

    This is in contrast to the statement in your post: “Pentair Hayward and Pentair both recommend 60-80 ppm of cyanuric acid for their salt systems.”

    • Well that’s good to see – Pentair finally adopting OUR standards! 🙂 Honestly, they did in the past, recommend much higher levels, until the new data came out about reduced chlorine effectiveness at higher cya levels.

  9. Dan Gomez

    I have a 20,000 gallon salt pool but my cyanuric acid level is reading 180ppm +!

    The salt cell runs constantly and can’t seem to keep the chlorine level above 0.6 leaving me adding dichlor granules weekly. Some have said drain the pool and start over.

    Others say don’t worry about high cyanuic acid levels as it will not affect chlorine generation. I need to know which to believe. Thanks!

    • Hi Dan, with cya at such a high level, it suppresses the activity of the chlorine so much that very little sanitation takes place. Many experts believe that when using cyanuric acid, you should also raise your minimum level of Free Chlorine and if at 70 ppm of cya, a pool should maintain FC levels at 4-5 ppm, to counteract the effect of the cyanuric. Now, most salt cell manufacturers suggest what I would call as high levels of cya, most manuf’s suggest 50-70 ppm, whereas I like to run 30-50 ppm. When you get over 100ppm it can become hard to maintain and test for good levels of FC, as you have mentioned. Double check the cya test to be sure, but if the reading is really 180 ppm, I would drain 80% of the pool and refill. How did it get that high too, would be another question. Dichlor contains cyanuric, about 30% by weight, but maybe dry cyanuric acid or stabilizer was added too?

      • Michael Peck

        Davy….Very informative response to Mr. Gomez. My cya level is in the same ballpark as Mr. Gomez’s. Using trichlor tablets for an extended period it’s not hard for it to build to such levels. I assume you regulate your cya level via periodic drainage. As you indicated a serious initial drainage will be in order. Based on your experience once this is done and cya is at desired level how often and how much drainage would you estimate to maintain the proper cya level while maintaining the optimum free chlorine level for a 20,000 gal. pool. Thank You.

        • Hi Michael, how fast cyanuric acid builds up in a pool depends on rain fall and fill-water rates to a large degree, and also if the pool operates year around, or winterizes. For pools that in the snowbelt, that get regularly rain fall and who backwash a sand or DE filter regularly, and then lower the water level by 1-2′ in winter, there usually is not a problem with cyanuric acid build-up. For pools in arid regions, with a cartridge filter, that operate year round, I understand that some pools using stabilized trichlor tablets (3″ tabs) can rise naturally to high levels within a few seasons, if some water replacement is not done. There is a product called Bio-Active that works to remove cyanuric acid levels, and this year Natural Chemistry is launching a product to remove cya. And since we are on a salt water pool chemistry blog post, if you use a salt chlorinator, this won’t add any cyanuric to the pool, only what you manually add to the pool water. Another way to reduce cyanuric acid build-up is to use a Nature2 Express purifier, or an ozonator or a UV system, or an ionizer – all of which can allow you to reduce your chlorine tablet consumption by as much as 50%, so 50% less cya added to the pool on a daily basis, should go twice as long before draining is needed.

  10. My salt level is at 4000 since the salt cell was cleaned and the cya is reading high. Are these levels safe to swim in? The water looks clear and beautiful.

    • The levels should be safe to swim in, although I don’t know if 4000 ppm is too high for your salt system, as each system has their own maximum level. Cyanuric acid – actually suppresses chlorine activity, and high cya levels can create unsafe swim water, in that chlorine levels which are fine without cya, are not sufficient to kill all bacteria, at a high cyanuric acid level. Experts say that for higher levels of cya, higher levels of chlorine should be maintained, to compensate for the reduced activity of the chlorine molecule, when combined with cya.

  11. Every time I talk to a pool person whether at a pool store or if I hire someone to service my pool. They all push the conditioner. I always feel like this is a upsell. My saltwater pool is 16,18K gl I think.
    What my question is, If I keep the acid, salt levels where they should be done, I really need conditioner? I feel it is one of the first things that are said “I need” when it’s really not….my system is pvc pipe.

    • Davy Merino

      Hi Pamela, it’s an upsell yes, but it is a necessary chemical to use with salt systems, and all salt system manufacturers recommend using conditioner (aka stabilizer, aka cyanuric acid), to protect chlorine from the sun, which depletes the chlorine rapidly and causes the salt cell to overwork during the sunny part of the day. If your pool is very heavily shaded, or indoors, you may not need to use it, but if you get several hours per day of sun directly on the pool, having a low level of cyanuric acid (20-40 ppm) is a good idea, for salt cell longevity. The harder the salt cell works, the shorter it will last, in most cases.

  12. frank garcia

    what about stains and fiberglass pools….do you still need a Sacrificial Anode? thank you

    • The sacrificial anode is not really to protect the pool surfaces, but the steel component surfaces like ladders, handrails, light bezels, or other chrome or steel items in the pool. They can develop a tarnish or loss of the shiny finish in salt pools, over time – but the anode will sacrifice itself, and attract all of the finish-damaging corrosion to itself

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