As a salt water pool owner, unless you’re testing your chlorine levels daily or have a live reading available, chances are you will experience the following: Your pool water slowly turns cloudy, a bit of algae starts setting in and you need to take a closer look to see what is happening.
Chances are, you are no longer producing chlorine or possibly aren’t producing enough for your pool’s needs.
The main reasons why your salt water pool is showing 0 chlorine available in the water is as follows:
- Salt level is too low.
- Problem with the salt cell or chlorinator itself.
- Chlorinator run time is too low for the needs of the pool.
- Pump run time is too low for the needs of the pool.
- Cyanuric acid (stabilizer) is too low.
- Chlorine lock is present.
- Other water balancing problem.
- Torrential rain which dilutes the chlorine in your pool.
Below we will discuss each in more detail and how to deal with the problem.
Salt level is too low
The level of salt in your salt water pool is typically best set between 2700 ppm to 3400 ppm (parts per million). Check your chlorinator owner’s manual to be safe but that’s the normal range. If your salt level is a bit high, it will come down during the season as water is lost through splashing, leaks (if you have one) and back washing if you have that type of filtration system.
But if your salt level is too low, it means your chlorinator will have to work harder to produce chlorine which is stressful on the salt cell and will quickly lead to cloudy water.
At some point, your chlorinator will shut down and stop producing chlorine to protect itself when the salt level drops below a certain level. This will remain until you add the necessary level of salt to the water.
Solution: Test salt levels frequently if you have to do it manually. Many modern chlorinators have a built-in live salt reading that gives an instant measurement which is a handy tool. Add salt as required.
Problem with the salt cell or chlorinator itself
Salt water pool owners often discover that there is a problem with the salt cell (it’s dirty or damaged, has reached its end of lifespan) or the chlorinator system itself (electrical problem or other malfunction).
But unless you’re testing chlorine regularly, you might not notice until the water starts getting cloudy and algae is forming. By then it’s likely you’re already at 0 chlorine especially if you’re seeing sunny weather and have been using the pool frequently.
A modern chlorinator system has alerts that will let you know if the salt cell needs servicing or is no longer working, if salt levels are too low or high, etc.
Solution: Test water regularly particularly for chlorine. Test strips are pretty cheap and quick and easy to use. If your chlorinator has warnings and alerts for salt cell problems, check the unit every few days to ensure no warnings are present.
Chlorinator run time is too low for the needs of the pool
Your chlorinator can typically be set to run at a percentage of time based on when the pump is running. So if your chlorinator is set to 70%, it means that 70% of the time the pump is running, the chlorinator will also run and produce chlorine.
I generally run my chlorinator around 50% and that suffices but you might need something different.
Solution: If your chlorinator run percentage is set too low, it’s possible you will need to increase the rate so that chlorine is produced more frequently.
Of course you need to have the pump running for the chlorinator to produce chlorine. With that in mind, another problem you might have is…
Pump run time is too low for the needs of the pool
When your pump is running, the chlorinator can also operate and produce chlorine. When the pump is shut off, the chlorinator cannot function and thus no chlorine will be produced.
If you are (for example) only running your pump 8 hours per day and find it’s difficult to produce enough chlorine, you have the option of increasing your chlorinator run percentage (please refer to the paragraph above) and/or the pump running time.
Solution: With a bit of trial and error, you will find out how to balance both your pump and chlorinator run times. You want a happy medium – both the pump and chlorinator are running just enough to properly filter the water and produce enough chlorine – rather than running one too high and the other too low.
It’s generally accepted to run your pump at least 8 – 10 hours per day but your local weather and swimming conditions might require something a bit different.
Cyanuric acid (stabilizer) is too low
Cyanuric acid (CYA) should be added to your salt water pool to maintain a rate of 60 ppm at the low end and 80 ppm (ideal) to protect the chlorine in the water for the sun’s harmful rays. Chlorine can break down into a gas that exits your pool in as little as 2 hours of sunlight.
This is why you will see commercially purchased chlorine products with “Stabilized Chlorine” on the label: It has stabilizer added to it.
The chlorine produced by your pool’s chlorinator does not have stabilizer built in which is why we need to add CYA manually.
Plus, chlorinators don’t quickly increase the chlorine level in your pool the way you can by shocking the water with a concentrated chemical chlorine product. Instead, they keep a steady level of chlorine, producing just enough to sanitize your pool.
Solution: Maintaining stabilizer at 60 ppm – 80 ppm in your pool is critical to protecting the chlorine in your pool and allowing it to accumulate over time so that it can effectively sanitize your water.
Chlorine lock is present
A chlorine lock refers to a large disparity between the free chlorine and total chlorine in the water. Normally these numbers should be fairly close.
But if you add too much cyanuric acid, it can prevent the chlorine in your pool from doing its job (sanitizing the pool by killing bacteria) and a chlorine or bleach-type smell emanates from your pool as a result.
This may cause you to think you have too much chlorine in the water but this is not the case. It’s actually too much CYA most likely and a lack of chlorine that you’re experiencing.
Solution: Depending on the specific case you’re facing, you might drain some pool water and refill with fresh water.
You can also use a non-chlorine-based shock product to oxidize the chlorine in your pool. The formula I was told to use to calculate shock requirements is:
(Total Chlorine – Free Chlorine) x (Number of gallons of water in your pool / 10,000) x 2 = lbs of non-chlorine shock to add.
So if your Total Chlorine is showing 5, Free Chlorine is currently 3 and your pool has 20,000 gallons of water, you would need: (5 – 3) x (20,000/10,000) x 2 = 8 lbs of non-chlorine shock required.
If in doubt or the process is simply too time-consuming to resolve, save yourself the bother: Take a water sample to your trusted pool company and get a diagnosis. Sure, they might try to sell you some products – you can always tell them you have the necessary chemicals if you want to buy it somewhere else – but the swimming season is short. The quicker you get the problem resolved the better.
Other water balancing problem
Low pH is another common reason for low or no chlorine build up in your pool. The ideal pH level in a salt water pool is 7.2 to 7.8. pH often drifts higher in salt water pools specifically due to Sodium Hydroxide produced during chlorine production. If your CYA (stabilizer) is too high, pH can also go higher as a result. Excessively high Total Alkalinity (TA) can also cause a rise in your pH.
Solution: Click here to learn more about lowering your pH as it’s a common problem in salt water pools.
You can also learn more about overall water balancing and the 7 main factors of balanced water in a salt water pool including maintaining your TA. These are important topics that will help you become more self sufficient and less reliant on your pool company.
Torrential rain which dilutes the chlorine in your pool
Torrential rain can quickly increase the water level in your pool, causing you to need to drain water. The extra water in your pool can quickly dilute chlorine but the necessary draining of water can further reduce your chlorine to 0.
If you receive a large amount of water in a short period of time, whether you need to drain water or not might mean shocking your pool water either with the Super Chlorinate feature of your chlorination system or possibly with chemical chlorine.
Using chemical chlorine is quicker and also less taxing on your salt cell so that’s typically what I do.
Summary
There are a number of main reasons that chlorine can be low in your salt water pool at any given time. The ones listed and discussed above are the main ones in my experience.
The more automated your chlorinator system, the quicker you’ll be alerted to various problems although testing your pool water with test strips at least once per week helps too.
The longer you own your pool, the better you can get at quickly troubleshooting various problems so you have to rely less on your pool company.