What is your CYA level?

Are you shocking appropriately for your CYA level?

Have you done the overnight CL test after shocking properly?

Try trouble free pools website, it will help guide you.

CYA level is fine at 50.

However, cya levels would not explain a CL level of zero with the chlorinator set to maximum output.

You have algae so you need to shock. Your chlorinator will produce a baseline level of chlorine but will not generate shock levels of chlorine. Any chlorine being produced by your generator right now is being used up in a losing battle with the algae so it shows zero chlorine. It is amazing how fast it can be used up. To know what your levels of chlorine need to be for both maintenance and shock levels depends on your CYA level. I tried to post the the link to trouble free pool but it blocked me. Go there and you'll find everything in Pool School that you need. Let us know if it doesn't make sense.

An IC-40 is too small for your pool. You need an IC-60.

Cells are rated by the maximum amount of FC generated in a 24 hour period. Is your pump normally running that long? Most are not.

Scott

Scott,

I told my pb about your response- that the unit was undersized. His response was that he has never needed to use anything larger than an IC-40. They tested the unit yesterday and it is producing chlorine. It seems that it must be undersized for my pool. They are still testing the unit running it at high speed and chlorine level today still reads zero. Any suggestions on how to approach my pb? This is getting ridiculous. Even if it went to 1 ppm what would that prove at this point? ( But it will be zero in the morning once again).

The IC40 being undersized is not the problem now, it is algae. Even if you had the IC60 it would not matter, they cant produce enough chlorine to kill an algae bloom, you have to do so by adding chlorine manually. Please go to trouble free pool dot com and read pool school on how to deal with algae.

All that will happen with the IC40 (once you have defeated the algae) is that it will have to run at a higher percentage and possibly longer pump run times to keep your pool chlorinated than a larger unit would. The units last for only so much "run time" so you will not get as many years with an IC40 as you would the IC60. But as I said before, any chlorine you are producing now is getting used up too quickly for you to detect it. You need to shock. Time is money. You will need a lot more chlorine for a longer time the longer you wait.

I stand by what I said. If there was enough free chlorine (FC), he would not have gotten the algae. The output of a cell should not be used to kill it. Cells are intended to only produce maintenance levels even though some have a 24 hour boost cycle.

Cells have two states, on and off. The percentage of time it is on is usually portrayed as the power level when it should be represented as a function of the amount of time per hour it is on. Most cells have a design life of 10,000 hours of on time. Boost cycles just turn the cell on all the time, shortening the life of the cell.

For building a residual or starting the shock process, I recommend using another chlorine elevator such as unscented bleach, 10-12% chlorinating liquid, cal-hypo or dichlor.

WRT the original problem, I have to assume the OP is running his cell for too short a period and at too low a power and relying on OTO drops and test strips. They aren't going to cut it, especially when shocking levels of FC are needed. A good kit with an FAS-DPD test such as found in the Taylor K-2006 for TF-100 (better value for homeowners) is needed.

Scott

I agree with what you're saying that his initial power level of 50% and whatever pump run time he had was not chlorinating adequately. He states he always had zero FC at that setting. It seems no sdjustments were made until the algae showed up, and then it was too late to rely on the SWCG no matter what setting. He won't know until the algae bloom is dealt with if this SWCG will produce enough. Once shocking has killed the algae, he should likely run it at 100% and decrease if he can based on testing results. I also agree that if the PB will get him an IC-60, that would be best. If not, he can get the bigger cell when it comes time to replace. Of course, if the IC-40 will not keep up at all, that would hopefully prove to the PB that he needs the bigger cell.

Thanks for all of your responses.

I should clarify that my water has almost always been crystal clear, even now that I have some brown patches of algae (not staining from fe or mn) on the walls in the deep end of the pool. I have closely followed and maintained the water chemistry with the TF-100 kit you mention, Scott. I am not tryong to control an algae bloom with thue chlorinator. My point is that there has never been a trace of chlorine in the pool other than the traces left after shocking.
The unit has a shock cycle whereby it superchlorinates,ie, runs at 100% for 2 consecutive 12hour cycles. It is supposed to raise the cl to greater than 10ppm. However, I cant even get 0.5 ppm after running it consecutive cycles nonstop over several days.
I spoke to my pb this am. He has agreed to talk to the Pentair rep but I dont want them to simply replace it with another IC 40 which appears to be undersized for my pool. The present one has already been tested-the cell is working properly- it is making chlorine.I want pb to replace with the IC 60. I already told my pb I wouldpay the upcharge for the bigger unit.

I have a 30,000 gallon pool and an IC40. They are rated up to 40,000 gallons. I have never had a problem. I run mine 24/7 @ 60%. Been this way for over 3 years.
Apparently, your initial setting of 50% was not enough to keep an algae bloom from taking hold.

I bought a IC40 couple of year back. I think it failed after few months of installation. No chlorine at all. I called their customer support. They kept on relating it to either phosphate or hot weather. Finally I found on you tube how to test it. Pour water run it ... it should generate some bubbles. I did, but no bubbles what so ever. That means unit doesn't work at all, despite all lights showing green. My pool size is 11000 and salt is at 4000 level.

I was thinking to say good bye to IC for ever and go for a different company but is there any one who has gone further in the cell testing.

Its frustrating for a how much these companies are charring for a piece of garbage. Hardly anything in a cell. A Laptop which has so many sophisticated components can be easily bought for under $400 but his crap which hardly has even item worth $100 is sold for $800 or so. That too most of these cell fails.