Chlorine Level in salt water pool

  • Last Post 13 September 2016
  • Topic Is Solved
JEOster posted this 23 August 2016

I have a new 20x35 salt water pool with a Pentair control box. I'm not convinced that my Intellichlor chlorinator is working properly. The chlorine level is almost always reading 0 and my pool builder says that is normal since it's a salt water. The greenlights are on except for the ones that show the percentage of chlorination it is set on (set at 75% currently). The only time those lights come on is when I set it to superchlorinate and then they all come on. Thoughts? Should I get a chlorine reading on the test strip? Is it measuring free vs total chlorine?

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InyoAlan posted this 13 September 2016

Excellent!!! Thank you and have a great rest of your season.


JEOster posted this 13 September 2016

Thank you for the follow up. We have been able to get the issue resolved. It was a scheduling issue on our control box. We are producing chlorine!

InyoAlan posted this 13 September 2016

Hello JEOster,

Just checking up on you to see if you have been getting a chlorine reading. You would want to take a water sample at the jet. Place your thumb over the hole in the bottle, and then retrieve a sample directly from the jet. Turn the salt system to 100% and let it run 10-15 min before taking the sample. You can test for chlorine at home or at a local pool store within one hour of retrieving the water sample. The chloring level should be regestiering high. If you have 0 on the chlorine reading, your salt system is not working. Also, remember the salt level should read between 2900-3200 ppm.

Thank you,


JEOster posted this 28 August 2016

Thanks. We've made some progress. We got the right lights to turn on with the chlorinator (it was on a spa setting-- which we don't have). Anyway, we had it running at 80% for the last 24 hours but no detectable chlorine level. So, again still not sure if it's working. I'll try taking a sample by the inlet and see if I get a reading.

Surprisingly, the pool is crystal clear right now. We added clear aid, dry acid and clarifier. No algae, phophates are a little high(400) and ph a little high (8.0).

We also checked and cleaned the cell in the chlorinator.

Service posted this 28 August 2016

Jeoster, I would also highly recommend a liquid test kit instead of the strips as we found the strips to be unreliable. One way to see if your salt system is creating chlorine is to test the water which is coming directly out of your jet. If you were salt system is working then this water should be highly concentrated with chlorine. I have tried this with a test strip but the jet blows the test strip apart so you really only can do this with a liquid test kit.

Thank You


InyoRob posted this 26 August 2016

The cloudiness is the first sign of an algae bloom. We would recommend shocking the pool with dry shock (cal-hypo) or liquid chlorine (sodium hypochlorite). You'll want to bring the free chlorine level up around 24 ppm. This should kill anything organic. Once the pool is free of any organic matter, the salt system should be able to take over and maintain the chlorine level.

JEOster posted this 26 August 2016

To be honest, I'm not sure if I have an algae problem. The pool had been cloudy. Last week, we added a clarifier (with algaecide) which cleared the water. Now, it's starting to get cloudy again. If algae is a problem, not sure if it's the chicken or egg with the chlorine level.

Do you recommend adding supplemental chlorine to get the level up and then see what the chlorinator does after that? Once the chlorine level is up 1-4ppm, it should be able to maintain that level, right?

I will double check the plates though. It's less than a month old so I expect them to be ok.

InyoRob posted this 26 August 2016

Is there any algae in the pool? If so, it is very hard to get a chlorine reading because it's being used up trying to kill the algae.

If algae is not the issue, it may be time to clean or replace the cell. Check the plates on the inside of the cell. Clean the cell if there is scale covering the plates. If you clean the cell and it still doesn't produce chlorine it's probably time to replace it.

JEOster posted this 25 August 2016

Thanks for the quick follow-up.

Other than the chlorine, everything else is in good shape... FAC = 0 SALT = 2900 HARDNESS = 240 CYA = 65 ALKALINITY = 120 PH = 7.7 Phosphates = 400 Temp = 87

Last night I set the superchlorinator to run 8pm-8am, when I tested it at 6pm tonight it still read 0.

All the lights are green on the chlorinator and when I set it to superchlorinate the lights come on as expected.

Is there a way to tell if it's working properly?

InyoRob posted this 24 August 2016

Hello JEOster - Salt water systems generate chlorine. Therefore, you should be getting a chlorine reading. A lot of the test strips will test the free and total chlorine. 

Are you able to test the stabilizer (cyanuric acid) level?  The stabilizer level is really important because it acts as sunscreen for chlorine. If the stabilizer is too low, the sunlight will quickly burn off your chlorine. If the stabilizer level is too high, it will make the chlorine ineffective.