Chlorine levels very low


New member
May 13, 2017
I am having trouble getting free chlorine levels up to 1.0-3.0. My latest test results are:

Total Chlorine: 1.0
Free Chlorine: 0.0
pH: 7.2
Total Alkalinity:100
Calcium Hardness: 225
Stabilizer: 60

My chlorinator is working plus I have added tablets to both skimmers. over the past week I have added at least 10 # of Super shock. Additionally, I added 10# of Chlorinating concentrate within the past 24 hours.

Nothing I have done so far has raised the Free Chlorine levels.


TFP Expert
LifeTime Supporter
Jan 6, 2010
San Dimas, CA (LA County)
Welcome! :wave:

I'm guessing the water isn't clear, or at least not crystal clear.

First thing: stop adding tablets. They contain chlorine and CYA and you already have enough CYA.
Second, FC + CC = TC. Or TC-FC = CC. In your case, 1TC -0FC = 1 CC. Something is reacting to the chlorine you're putting in and creating combined chloramines. You need to kill it with sustained high doses of chlorine

What you need is a lot of bleach. Or liquid shock or pool chlorinating liquid or whatever they label it as. It's all the same stuff: Sodium Hypochlorite. Specific instructions on how much to add and all the rest are in the SLAM article. Please look closely at the prerequisites, especially regarding test kits. If your only chlorine test uses colormatching, it won't work.

Here's a recent (finished today) thread that shows you how the SLAM process works.


New member
May 13, 2017
Actually I forgot to mention that the water is crystal clear!!! And this is only 10 days after opening the pool. It came out of winterization looking pretty good. I have a loop lock cover and the pool just had a few leafs in it when we opened it. It cleared up within 96 hours but still won't hold any chlorine.


Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
Bedford, TX

Well, it's not magic... If you put chlorine in, it has to get used up by sunlight or by something consuming it, or it would still be there.

With a CYA of 60, it should not be the sunlight.. (Of course that assumes the 60 ppm of CYA is an accurate number.. Where did this number come from??)

You can confirm if something (algae) is consuming your FC by doing what we call an OCLT.. See this...

Basically add chlorine after dark, wait 30 minutes and test and record the results... Get your rear out of bed before sunrise and test again. If you loose more than 1 ppm overnight, you have an algae outbreak.

Of course this requires you to have an accurate test kit.. What test kit are you currently using to test your water?


Jim R.


New member
May 13, 2017
I have been taking the water sample to my local pool store. They use the standard test strips. I haven't used a full up test analysis kit in years but recognize that it is probably necessary in this case. The 60 CYA number comes from a test on 5/12/17. I added the 10 pounds of Chlorinating concentrate after the test the same day and let the pool circulate it over night. I took a sample back to the same store on 5/13/17 and the FC was still 0.0 but the CYA had dropped to 20, the pH dropped from 7.2 to 6.8, the total alkalinity dropped from 100 to 75, and the calcium hardness dropped from 225 to 200. The pool is about 11 years old. I am the second owner and have been here for 4 years. To my knowledge, the pool has never been drained (except about 18 inches to winterize it each year). This year I made up most of the 18 inches by letting it fill up with rain water starting 1 March.

They recommend using "Revive" which is supposed to remove orthophosphates, copper, iron and generally clear the water of organic debris. So I am going through this process now. I am running the filter and having to backwash about every 5 -6 hours so this stuff is taking something out of the water. Right now my plan is to continue this for another 24 hours or until I quit having to backwash so often. This morning the water is still crystal clear! The next step they recommend is to add 20 pounds of "Easy Pool" which is a concentrated pool blend. That won't happen until tomorrow morning at the earliest.

Before anyone starts to think that they are just selling me chemicals, they have refused to charge me for the 10 pounds of Chlorinating concentrate or the "Revive" or "Easy Pool" unless it works! So far nothing has. These are honest guys. This is a small Midwest town and they have a reputation to protect.


Bronze Supporter
LifeTime Supporter
TFP Guide
Jun 3, 2015
Hmm, they give you 'Revive' to remove copper, then give you 'Easy Pool' which adds copper. Puzzling.

I'm sure they mean well, and want to help, but products that add copper should really be avoided. Regular use of these products will eventually cause staining of pool surfaces, as well as turn hair & fingernails green.

I hope that your pool clears up to your satisfaction. Remember to keep FC above 7.5% of your CYA at all times.


TFP Expert
LifeTime Supporter
Apr 27, 2012
Grand Rapids, MI
OK3, I just want to clarify whether you'd like further assistance, and make sure you understand why this particular forum may not be able to offer it if you're relying on pool store readings. Because we'd LOVE to help you, but our hands are kinda tied when a poster follows typical pool store advice.

That's because the founding principal of TFP is based on science that shows keeping FC at 7.5% of your CYA level will eliminate algae problems. But most pool store products except liquid chlorine are stabilized products, meaning they incrementally add CYA...which makes it a moving target.

In addition, cya testing is difficult even poolside with the recommended kit, and notoriously inaccurate at most pool stores.

So to diagnose problems, we always need to know first that the FC ratio is correct as a baseline. And we can't do that in good conscious with any other test ;)

With SWG there are a variety of things to look at, including age of cell, sizing for pool, salt levels, current, etc. There are also a variety of things that create a high chlorine demand, including nascent algae and even things like antifreeze getting into the pool on opening if lines are flushed back into the pool.

If you raise your FC with liquid chlorine repeatedly until it holds at its recommended level (if you had a proper test kit) you would be able to rule out nascent algae, or oxidize any chemical fighting your chlorine, etc. You are then in a better position to diagnose, or ave us help diagnose, what's going on.

Have a read through Pool School to see what you think about our maintenance approach before adding the Easy Pool.

While I don't doubt your guys are honest and believe in their system, which is in the interest of the mfgs that sell to them to promote, at the end of the day I'd rather teach you to fish than give you a fish. The pool store guys are giving you a fish, and you're paying for it, and the convenience of that is probably attractive, so its your call and we do undrstand. But learning to fish the TFP way empowers you to have a trouble free pool, so I invite your consideration ;)